From 44343c777ca8c02262d1d381a2cc24866b3c5414 Mon Sep 17 00:00:00 2001
From: Brian Kessler <brian.m.kessler@gmail.com>
Date: Tue, 23 Apr 2019 22:04:38 -0600
Subject: [PATCH] cmd/compile: add signed divisibility by power of 2 rules
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

For powers of two (c=1<<k), the divisibility check x%c == 0 can be made
just by checking the trailing zeroes via a mask x&(c-1) == 0 even for signed
integers. This avoids division fix-ups when just divisibility check is needed.

To apply this rule, we match on the fixed-up version of the division. This is
neccessary because the mod and division rewrite rules are already applied
during the initial opt pass.

The speed up on amd64 due to elimination of unneccessary fix-up code is ~55%:

name                     old time/op  new time/op  delta
DivconstI64-4            2.08ns ± 0%  2.09ns ± 1%     ~     (p=0.730 n=5+5)
DivisiblePow2constI64-4  1.78ns ± 1%  0.81ns ± 1%  -54.66%  (p=0.008 n=5+5)
DivconstU64-4            2.08ns ± 0%  2.08ns ± 0%     ~     (p=0.683 n=5+5)
DivconstI32-4            1.53ns ± 0%  1.53ns ± 1%     ~     (p=0.968 n=4+5)
DivisiblePow2constI32-4  1.79ns ± 1%  0.81ns ± 1%  -54.97%  (p=0.008 n=5+5)
DivconstU32-4            1.78ns ± 1%  1.80ns ± 2%     ~     (p=0.206 n=5+5)
DivconstI16-4            1.54ns ± 2%  1.54ns ± 0%     ~     (p=0.238 n=5+4)
DivisiblePow2constI16-4  1.78ns ± 0%  0.81ns ± 1%  -54.72%  (p=0.000 n=4+5)
DivconstU16-4            1.00ns ± 5%  1.01ns ± 1%     ~     (p=0.119 n=5+5)
DivconstI8-4             1.54ns ± 0%  1.54ns ± 2%     ~     (p=0.571 n=4+5)
DivisiblePow2constI8-4   1.78ns ± 0%  0.82ns ± 8%  -53.71%  (p=0.008 n=5+5)
DivconstU8-4             0.93ns ± 1%  0.93ns ± 1%     ~     (p=0.643 n=5+5)

A follow-up CL will address the general case of x%c == 0 for signed integers.

Updates #15806

Change-Id: Iabadbbe369b6e0998c8ce85d038ebc236142e42a
Reviewed-on: https://go-review.googlesource.com/c/go/+/173557
Run-TryBot: Brian Kessler <brian.m.kessler@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
---
 .../internal/gc/testdata/arith_test.go        |  291 ++++
 .../compile/internal/ssa/gen/generic.rules    |   35 +
 .../compile/internal/ssa/rewritegeneric.go    | 1546 ++++++++++++++++-
 .../compile/internal/test/divconst_test.go    |   26 +
 test/codegen/arithmetic.go                    |   21 +-
 5 files changed, 1910 insertions(+), 9 deletions(-)

diff --git a/src/cmd/compile/internal/gc/testdata/arith_test.go b/src/cmd/compile/internal/gc/testdata/arith_test.go
index 728ca56892f2a7..1ec9ae02c95fba 100644
--- a/src/cmd/compile/internal/gc/testdata/arith_test.go
+++ b/src/cmd/compile/internal/gc/testdata/arith_test.go
@@ -7,6 +7,7 @@
 package main
 
 import (
+	"math"
 	"runtime"
 	"testing"
 )
@@ -924,6 +925,7 @@ func TestArithmetic(t *testing.T) {
 	testShiftRemoval(t)
 	testShiftedOps(t)
 	testDivFixUp(t)
+	testDivisibleSignedPow2(t)
 }
 
 // testDivFixUp ensures that signed division fix-ups are being generated.
@@ -952,3 +954,292 @@ func testDivFixUp(t *testing.T) {
 		g64 = z % int64(i)
 	}
 }
+
+//go:noinline
+func divisible_int8_2to1(x int8) bool {
+	return x%(1<<1) == 0
+}
+
+//go:noinline
+func divisible_int8_2to2(x int8) bool {
+	return x%(1<<2) == 0
+}
+
+//go:noinline
+func divisible_int8_2to3(x int8) bool {
+	return x%(1<<3) == 0
+}
+
+//go:noinline
+func divisible_int8_2to4(x int8) bool {
+	return x%(1<<4) == 0
+}
+
+//go:noinline
+func divisible_int8_2to5(x int8) bool {
+	return x%(1<<5) == 0
+}
+
+//go:noinline
+func divisible_int8_2to6(x int8) bool {
+	return x%(1<<6) == 0
+}
+
+//go:noinline
+func divisible_int16_2to1(x int16) bool {
+	return x%(1<<1) == 0
+}
+
+//go:noinline
+func divisible_int16_2to2(x int16) bool {
+	return x%(1<<2) == 0
+}
+
+//go:noinline
+func divisible_int16_2to3(x int16) bool {
+	return x%(1<<3) == 0
+}
+
+//go:noinline
+func divisible_int16_2to4(x int16) bool {
+	return x%(1<<4) == 0
+}
+
+//go:noinline
+func divisible_int16_2to5(x int16) bool {
+	return x%(1<<5) == 0
+}
+
+//go:noinline
+func divisible_int16_2to6(x int16) bool {
+	return x%(1<<6) == 0
+}
+
+//go:noinline
+func divisible_int16_2to7(x int16) bool {
+	return x%(1<<7) == 0
+}
+
+//go:noinline
+func divisible_int16_2to8(x int16) bool {
+	return x%(1<<8) == 0
+}
+
+//go:noinline
+func divisible_int16_2to9(x int16) bool {
+	return x%(1<<9) == 0
+}
+
+//go:noinline
+func divisible_int16_2to10(x int16) bool {
+	return x%(1<<10) == 0
+}
+
+//go:noinline
+func divisible_int16_2to11(x int16) bool {
+	return x%(1<<11) == 0
+}
+
+//go:noinline
+func divisible_int16_2to12(x int16) bool {
+	return x%(1<<12) == 0
+}
+
+//go:noinline
+func divisible_int16_2to13(x int16) bool {
+	return x%(1<<13) == 0
+}
+
+//go:noinline
+func divisible_int16_2to14(x int16) bool {
+	return x%(1<<14) == 0
+}
+
+//go:noinline
+func divisible_int32_2to4(x int32) bool {
+	return x%(1<<4) == 0
+}
+
+//go:noinline
+func divisible_int32_2to15(x int32) bool {
+	return x%(1<<15) == 0
+}
+
+//go:noinline
+func divisible_int32_2to26(x int32) bool {
+	return x%(1<<26) == 0
+}
+
+//go:noinline
+func divisible_int64_2to4(x int64) bool {
+	return x%(1<<4) == 0
+}
+
+//go:noinline
+func divisible_int64_2to15(x int64) bool {
+	return x%(1<<15) == 0
+}
+
+//go:noinline
+func divisible_int64_2to26(x int64) bool {
+	return x%(1<<26) == 0
+}
+
+//go:noinline
+func divisible_int64_2to34(x int64) bool {
+	return x%(1<<34) == 0
+}
+
+//go:noinline
+func divisible_int64_2to48(x int64) bool {
+	return x%(1<<48) == 0
+}
+
+//go:noinline
+func divisible_int64_2to57(x int64) bool {
+	return x%(1<<57) == 0
+}
+
+// testDivisibleSignedPow2 confirms that x%(1<<k)==0 is rewritten correctly
+func testDivisibleSignedPow2(t *testing.T) {
+	var i int64
+	var pow2 = []int64{
+		1,
+		1 << 1,
+		1 << 2,
+		1 << 3,
+		1 << 4,
+		1 << 5,
+		1 << 6,
+		1 << 7,
+		1 << 8,
+		1 << 9,
+		1 << 10,
+		1 << 11,
+		1 << 12,
+		1 << 13,
+		1 << 14,
+	}
+	// exhaustive test for int8
+	for i = math.MinInt8; i <= math.MaxInt8; i++ {
+		if want, got := int8(i)%int8(pow2[1]) == 0, divisible_int8_2to1(int8(i)); got != want {
+			t.Errorf("divisible_int8_2to1(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int8(i)%int8(pow2[2]) == 0, divisible_int8_2to2(int8(i)); got != want {
+			t.Errorf("divisible_int8_2to2(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int8(i)%int8(pow2[3]) == 0, divisible_int8_2to3(int8(i)); got != want {
+			t.Errorf("divisible_int8_2to3(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int8(i)%int8(pow2[4]) == 0, divisible_int8_2to4(int8(i)); got != want {
+			t.Errorf("divisible_int8_2to4(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int8(i)%int8(pow2[5]) == 0, divisible_int8_2to5(int8(i)); got != want {
+			t.Errorf("divisible_int8_2to5(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int8(i)%int8(pow2[6]) == 0, divisible_int8_2to6(int8(i)); got != want {
+			t.Errorf("divisible_int8_2to6(%d) = %v want %v", i, got, want)
+		}
+	}
+	// exhaustive test for int16
+	for i = math.MinInt16; i <= math.MaxInt16; i++ {
+		if want, got := int16(i)%int16(pow2[1]) == 0, divisible_int16_2to1(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to1(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[2]) == 0, divisible_int16_2to2(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to2(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[3]) == 0, divisible_int16_2to3(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to3(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[4]) == 0, divisible_int16_2to4(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to4(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[5]) == 0, divisible_int16_2to5(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to5(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[6]) == 0, divisible_int16_2to6(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to6(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[7]) == 0, divisible_int16_2to7(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to7(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[8]) == 0, divisible_int16_2to8(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to8(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[9]) == 0, divisible_int16_2to9(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to9(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[10]) == 0, divisible_int16_2to10(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to10(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[11]) == 0, divisible_int16_2to11(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to11(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[12]) == 0, divisible_int16_2to12(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to12(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[13]) == 0, divisible_int16_2to13(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to13(%d) = %v want %v", i, got, want)
+		}
+		if want, got := int16(i)%int16(pow2[14]) == 0, divisible_int16_2to14(int16(i)); got != want {
+			t.Errorf("divisible_int16_2to14(%d) = %v want %v", i, got, want)
+		}
+	}
+	// spot check for int32 and int64
+	var (
+		two4  int64 = 1 << 4
+		two15 int64 = 1 << 15
+		two26 int64 = 1 << 26
+		two34 int64 = 1 << 34
+		two48 int64 = 1 << 48
+		two57 int64 = 1 << 57
+	)
+	var xs = []int64{two4, two4 + 3, -3 * two4, -3*two4 + 1,
+		two15, two15 + 3, -3 * two15, -3*two15 + 1,
+		two26, two26 + 37, -5 * two26, -5*two26 + 2,
+		two34, two34 + 356, -7 * two34, -7*two34 + 13,
+		two48, two48 + 3000, -12 * two48, -12*two48 + 1111,
+		two57, two57 + 397654, -15 * two57, -15*two57 + 11234,
+	}
+	for _, x := range xs {
+		if int64(int32(x)) == x {
+			if want, got := int32(x)%int32(two4) == 0, divisible_int32_2to4(int32(x)); got != want {
+				t.Errorf("divisible_int32_2to4(%d) = %v want %v", x, got, want)
+			}
+
+			if want, got := int32(x)%int32(two15) == 0, divisible_int32_2to15(int32(x)); got != want {
+				t.Errorf("divisible_int32_2to15(%d) = %v want %v", x, got, want)
+			}
+
+			if want, got := int32(x)%int32(two26) == 0, divisible_int32_2to26(int32(x)); got != want {
+				t.Errorf("divisible_int32_2to26(%d) = %v want %v", x, got, want)
+			}
+		}
+		// spot check for int64
+		if want, got := x%two4 == 0, divisible_int64_2to4(x); got != want {
+			t.Errorf("divisible_int64_2to4(%d) = %v want %v", x, got, want)
+		}
+
+		if want, got := x%two15 == 0, divisible_int64_2to15(x); got != want {
+			t.Errorf("divisible_int64_2to15(%d) = %v want %v", x, got, want)
+		}
+
+		if want, got := x%two26 == 0, divisible_int64_2to26(x); got != want {
+			t.Errorf("divisible_int64_2to26(%d) = %v want %v", x, got, want)
+		}
+
+		if want, got := x%two34 == 0, divisible_int64_2to34(x); got != want {
+			t.Errorf("divisible_int64_2to34(%d) = %v want %v", x, got, want)
+		}
+
+		if want, got := x%two48 == 0, divisible_int64_2to48(x); got != want {
+			t.Errorf("divisible_int64_2to48(%d) = %v want %v", x, got, want)
+		}
+
+		if want, got := x%two57 == 0, divisible_int64_2to57(x); got != want {
+			t.Errorf("divisible_int64_2to57(%d) = %v want %v", x, got, want)
+		}
+
+	}
+}
diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index 510cec0f4b7cd4..80429286165e66 100644
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -1163,6 +1163,41 @@
 (Mod64u <t> x (Const64 [c])) && x.Op != OpConst64 && c > 0 && umagicOK(64,c)
   -> (Sub64 x (Mul64 <t> (Div64u <t> x (Const64 <t> [c])) (Const64 <t> [c])))
 
+// Divisibility check for signed integers for power of two constant are simple mask.
+// However, we must match against the rewritten n%c == 0 -> n - c*(n/c) == 0 -> n == c *(n/c)
+// where n/c contains fixup code to handle signed n.
+(Eq8 n (Lsh8x64
+  (Rsh8x64
+    (Add8  <t> n (Rsh8Ux64  <t> (Rsh8x64  <t> n (Const64 <typ.UInt64> [ 7])) (Const64 <typ.UInt64> [kbar])))
+    (Const64 <typ.UInt64> [k]))
+	(Const64 <typ.UInt64> [k]))
+) && k > 0 && k < 7 && kbar == 8 - k
+  -> (Eq8 (And8 <t> n (Const8 <t> [int64(1<<uint(k)-1)])) (Const8 <t> [0]))
+
+(Eq16 n (Lsh16x64
+  (Rsh16x64
+    (Add16 <t> n (Rsh16Ux64 <t> (Rsh16x64 <t> n (Const64 <typ.UInt64> [15])) (Const64 <typ.UInt64> [kbar])))
+    (Const64 <typ.UInt64> [k]))
+	(Const64 <typ.UInt64> [k]))
+) && k > 0 && k < 15 && kbar == 16 - k
+  -> (Eq16 (And16 <t> n (Const16 <t> [int64(1<<uint(k)-1)])) (Const16 <t> [0]))
+
+(Eq32 n (Lsh32x64
+  (Rsh32x64
+    (Add32 <t> n (Rsh32Ux64 <t> (Rsh32x64 <t> n (Const64 <typ.UInt64> [31])) (Const64 <typ.UInt64> [kbar])))
+    (Const64 <typ.UInt64> [k]))
+	(Const64 <typ.UInt64> [k]))
+) && k > 0 && k < 31 && kbar == 32 - k
+  -> (Eq32 (And32 <t> n (Const32 <t> [int64(1<<uint(k)-1)])) (Const32 <t> [0]))
+
+(Eq64 n (Lsh64x64
+  (Rsh64x64
+    (Add64 <t> n (Rsh64Ux64 <t> (Rsh64x64 <t> n (Const64 <typ.UInt64> [63])) (Const64 <typ.UInt64> [kbar])))
+    (Const64 <typ.UInt64> [k]))
+	(Const64 <typ.UInt64> [k]))
+) && k > 0 && k < 63 && kbar == 64 - k
+  -> (Eq64 (And64 <t> n (Const64 <t> [int64(1<<uint(k)-1)])) (Const64 <t> [0]))
+
 (Eq(8|16|32|64)  s:(Sub(8|16|32|64) x y) (Const(8|16|32|64) [0])) && s.Uses == 1 -> (Eq(8|16|32|64)  x y)
 (Neq(8|16|32|64) s:(Sub(8|16|32|64) x y) (Const(8|16|32|64) [0])) && s.Uses == 1 -> (Neq(8|16|32|64) x y)
 
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index fe2fbb82c09af6..d30e65b7f18d95 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -98,17 +98,17 @@ func rewriteValuegeneric(v *Value) bool {
 	case OpDiv8u:
 		return rewriteValuegeneric_OpDiv8u_0(v)
 	case OpEq16:
-		return rewriteValuegeneric_OpEq16_0(v)
+		return rewriteValuegeneric_OpEq16_0(v) || rewriteValuegeneric_OpEq16_10(v)
 	case OpEq32:
-		return rewriteValuegeneric_OpEq32_0(v)
+		return rewriteValuegeneric_OpEq32_0(v) || rewriteValuegeneric_OpEq32_10(v)
 	case OpEq32F:
 		return rewriteValuegeneric_OpEq32F_0(v)
 	case OpEq64:
-		return rewriteValuegeneric_OpEq64_0(v)
+		return rewriteValuegeneric_OpEq64_0(v) || rewriteValuegeneric_OpEq64_10(v)
 	case OpEq64F:
 		return rewriteValuegeneric_OpEq64F_0(v)
 	case OpEq8:
-		return rewriteValuegeneric_OpEq8_0(v)
+		return rewriteValuegeneric_OpEq8_0(v) || rewriteValuegeneric_OpEq8_10(v)
 	case OpEqB:
 		return rewriteValuegeneric_OpEqB_0(v)
 	case OpEqInter:
@@ -8775,6 +8775,7 @@ func rewriteValuegeneric_OpDiv8u_0(v *Value) bool {
 }
 func rewriteValuegeneric_OpEq16_0(v *Value) bool {
 	b := v.Block
+	typ := &b.Func.Config.Types
 	// match: (Eq16 x x)
 	// cond:
 	// result: (ConstBool [1])
@@ -8951,6 +8952,389 @@ func rewriteValuegeneric_OpEq16_0(v *Value) bool {
 		v.AuxInt = b2i(c == d)
 		return true
 	}
+	// match: (Eq16 n (Lsh16x64 (Rsh16x64 (Add16 <t> n (Rsh16Ux64 <t> (Rsh16x64 <t> n (Const64 <typ.UInt64> [15])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 15 && kbar == 16 - k
+	// result: (Eq16 (And16 <t> n (Const16 <t> [int64(1<<uint(k)-1)])) (Const16 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh16x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh16x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd16 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		if n != v_1_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_1 := v_1_0_0.Args[1]
+		if v_1_0_0_1.Op != OpRsh16Ux64 {
+			break
+		}
+		if v_1_0_0_1.Type != t {
+			break
+		}
+		_ = v_1_0_0_1.Args[1]
+		v_1_0_0_1_0 := v_1_0_0_1.Args[0]
+		if v_1_0_0_1_0.Op != OpRsh16x64 {
+			break
+		}
+		if v_1_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_1_0.Args[1]
+		if n != v_1_0_0_1_0.Args[0] {
+			break
+		}
+		v_1_0_0_1_0_1 := v_1_0_0_1_0.Args[1]
+		if v_1_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_1_0_1.AuxInt != 15 {
+			break
+		}
+		v_1_0_0_1_1 := v_1_0_0_1.Args[1]
+		if v_1_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_1_1.AuxInt
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 15 && kbar == 16-k) {
+			break
+		}
+		v.reset(OpEq16)
+		v0 := b.NewValue0(v.Pos, OpAnd16, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst16, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst16, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq16 n (Lsh16x64 (Rsh16x64 (Add16 <t> (Rsh16Ux64 <t> (Rsh16x64 <t> n (Const64 <typ.UInt64> [15])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 15 && kbar == 16 - k
+	// result: (Eq16 (And16 <t> n (Const16 <t> [int64(1<<uint(k)-1)])) (Const16 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh16x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh16x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd16 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		v_1_0_0_0 := v_1_0_0.Args[0]
+		if v_1_0_0_0.Op != OpRsh16Ux64 {
+			break
+		}
+		if v_1_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0.Args[1]
+		v_1_0_0_0_0 := v_1_0_0_0.Args[0]
+		if v_1_0_0_0_0.Op != OpRsh16x64 {
+			break
+		}
+		if v_1_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0_0.Args[1]
+		if n != v_1_0_0_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_0_0_1 := v_1_0_0_0_0.Args[1]
+		if v_1_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_0_0_1.AuxInt != 15 {
+			break
+		}
+		v_1_0_0_0_1 := v_1_0_0_0.Args[1]
+		if v_1_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_0_1.AuxInt
+		if n != v_1_0_0.Args[1] {
+			break
+		}
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 15 && kbar == 16-k) {
+			break
+		}
+		v.reset(OpEq16)
+		v0 := b.NewValue0(v.Pos, OpAnd16, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst16, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst16, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq16 (Lsh16x64 (Rsh16x64 (Add16 <t> n (Rsh16Ux64 <t> (Rsh16x64 <t> n (Const64 <typ.UInt64> [15])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 15 && kbar == 16 - k
+	// result: (Eq16 (And16 <t> n (Const16 <t> [int64(1<<uint(k)-1)])) (Const16 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh16x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh16x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd16 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		if n != v_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_1 := v_0_0_0.Args[1]
+		if v_0_0_0_1.Op != OpRsh16Ux64 {
+			break
+		}
+		if v_0_0_0_1.Type != t {
+			break
+		}
+		_ = v_0_0_0_1.Args[1]
+		v_0_0_0_1_0 := v_0_0_0_1.Args[0]
+		if v_0_0_0_1_0.Op != OpRsh16x64 {
+			break
+		}
+		if v_0_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_1_0.Args[1]
+		if n != v_0_0_0_1_0.Args[0] {
+			break
+		}
+		v_0_0_0_1_0_1 := v_0_0_0_1_0.Args[1]
+		if v_0_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_1_0_1.AuxInt != 15 {
+			break
+		}
+		v_0_0_0_1_1 := v_0_0_0_1.Args[1]
+		if v_0_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_1_1.AuxInt
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 15 && kbar == 16-k) {
+			break
+		}
+		v.reset(OpEq16)
+		v0 := b.NewValue0(v.Pos, OpAnd16, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst16, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst16, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	return false
+}
+func rewriteValuegeneric_OpEq16_10(v *Value) bool {
+	b := v.Block
+	typ := &b.Func.Config.Types
+	// match: (Eq16 (Lsh16x64 (Rsh16x64 (Add16 <t> (Rsh16Ux64 <t> (Rsh16x64 <t> n (Const64 <typ.UInt64> [15])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 15 && kbar == 16 - k
+	// result: (Eq16 (And16 <t> n (Const16 <t> [int64(1<<uint(k)-1)])) (Const16 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh16x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh16x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd16 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		v_0_0_0_0 := v_0_0_0.Args[0]
+		if v_0_0_0_0.Op != OpRsh16Ux64 {
+			break
+		}
+		if v_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0.Args[1]
+		v_0_0_0_0_0 := v_0_0_0_0.Args[0]
+		if v_0_0_0_0_0.Op != OpRsh16x64 {
+			break
+		}
+		if v_0_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0_0.Args[1]
+		if n != v_0_0_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_0_0_1 := v_0_0_0_0_0.Args[1]
+		if v_0_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_0_0_1.AuxInt != 15 {
+			break
+		}
+		v_0_0_0_0_1 := v_0_0_0_0.Args[1]
+		if v_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_0_1.AuxInt
+		if n != v_0_0_0.Args[1] {
+			break
+		}
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 15 && kbar == 16-k) {
+			break
+		}
+		v.reset(OpEq16)
+		v0 := b.NewValue0(v.Pos, OpAnd16, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst16, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst16, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
 	// match: (Eq16 s:(Sub16 x y) (Const16 [0]))
 	// cond: s.Uses == 1
 	// result: (Eq16 x y)
@@ -9007,6 +9391,7 @@ func rewriteValuegeneric_OpEq16_0(v *Value) bool {
 }
 func rewriteValuegeneric_OpEq32_0(v *Value) bool {
 	b := v.Block
+	typ := &b.Func.Config.Types
 	// match: (Eq32 x x)
 	// cond:
 	// result: (ConstBool [1])
@@ -9183,7 +9568,390 @@ func rewriteValuegeneric_OpEq32_0(v *Value) bool {
 		v.AuxInt = b2i(c == d)
 		return true
 	}
-	// match: (Eq32 s:(Sub32 x y) (Const32 [0]))
+	// match: (Eq32 n (Lsh32x64 (Rsh32x64 (Add32 <t> n (Rsh32Ux64 <t> (Rsh32x64 <t> n (Const64 <typ.UInt64> [31])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 31 && kbar == 32 - k
+	// result: (Eq32 (And32 <t> n (Const32 <t> [int64(1<<uint(k)-1)])) (Const32 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh32x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh32x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd32 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		if n != v_1_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_1 := v_1_0_0.Args[1]
+		if v_1_0_0_1.Op != OpRsh32Ux64 {
+			break
+		}
+		if v_1_0_0_1.Type != t {
+			break
+		}
+		_ = v_1_0_0_1.Args[1]
+		v_1_0_0_1_0 := v_1_0_0_1.Args[0]
+		if v_1_0_0_1_0.Op != OpRsh32x64 {
+			break
+		}
+		if v_1_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_1_0.Args[1]
+		if n != v_1_0_0_1_0.Args[0] {
+			break
+		}
+		v_1_0_0_1_0_1 := v_1_0_0_1_0.Args[1]
+		if v_1_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_1_0_1.AuxInt != 31 {
+			break
+		}
+		v_1_0_0_1_1 := v_1_0_0_1.Args[1]
+		if v_1_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_1_1.AuxInt
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 31 && kbar == 32-k) {
+			break
+		}
+		v.reset(OpEq32)
+		v0 := b.NewValue0(v.Pos, OpAnd32, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst32, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst32, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq32 n (Lsh32x64 (Rsh32x64 (Add32 <t> (Rsh32Ux64 <t> (Rsh32x64 <t> n (Const64 <typ.UInt64> [31])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 31 && kbar == 32 - k
+	// result: (Eq32 (And32 <t> n (Const32 <t> [int64(1<<uint(k)-1)])) (Const32 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh32x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh32x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd32 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		v_1_0_0_0 := v_1_0_0.Args[0]
+		if v_1_0_0_0.Op != OpRsh32Ux64 {
+			break
+		}
+		if v_1_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0.Args[1]
+		v_1_0_0_0_0 := v_1_0_0_0.Args[0]
+		if v_1_0_0_0_0.Op != OpRsh32x64 {
+			break
+		}
+		if v_1_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0_0.Args[1]
+		if n != v_1_0_0_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_0_0_1 := v_1_0_0_0_0.Args[1]
+		if v_1_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_0_0_1.AuxInt != 31 {
+			break
+		}
+		v_1_0_0_0_1 := v_1_0_0_0.Args[1]
+		if v_1_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_0_1.AuxInt
+		if n != v_1_0_0.Args[1] {
+			break
+		}
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 31 && kbar == 32-k) {
+			break
+		}
+		v.reset(OpEq32)
+		v0 := b.NewValue0(v.Pos, OpAnd32, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst32, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst32, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq32 (Lsh32x64 (Rsh32x64 (Add32 <t> n (Rsh32Ux64 <t> (Rsh32x64 <t> n (Const64 <typ.UInt64> [31])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 31 && kbar == 32 - k
+	// result: (Eq32 (And32 <t> n (Const32 <t> [int64(1<<uint(k)-1)])) (Const32 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh32x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh32x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd32 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		if n != v_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_1 := v_0_0_0.Args[1]
+		if v_0_0_0_1.Op != OpRsh32Ux64 {
+			break
+		}
+		if v_0_0_0_1.Type != t {
+			break
+		}
+		_ = v_0_0_0_1.Args[1]
+		v_0_0_0_1_0 := v_0_0_0_1.Args[0]
+		if v_0_0_0_1_0.Op != OpRsh32x64 {
+			break
+		}
+		if v_0_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_1_0.Args[1]
+		if n != v_0_0_0_1_0.Args[0] {
+			break
+		}
+		v_0_0_0_1_0_1 := v_0_0_0_1_0.Args[1]
+		if v_0_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_1_0_1.AuxInt != 31 {
+			break
+		}
+		v_0_0_0_1_1 := v_0_0_0_1.Args[1]
+		if v_0_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_1_1.AuxInt
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 31 && kbar == 32-k) {
+			break
+		}
+		v.reset(OpEq32)
+		v0 := b.NewValue0(v.Pos, OpAnd32, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst32, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst32, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	return false
+}
+func rewriteValuegeneric_OpEq32_10(v *Value) bool {
+	b := v.Block
+	typ := &b.Func.Config.Types
+	// match: (Eq32 (Lsh32x64 (Rsh32x64 (Add32 <t> (Rsh32Ux64 <t> (Rsh32x64 <t> n (Const64 <typ.UInt64> [31])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 31 && kbar == 32 - k
+	// result: (Eq32 (And32 <t> n (Const32 <t> [int64(1<<uint(k)-1)])) (Const32 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh32x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh32x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd32 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		v_0_0_0_0 := v_0_0_0.Args[0]
+		if v_0_0_0_0.Op != OpRsh32Ux64 {
+			break
+		}
+		if v_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0.Args[1]
+		v_0_0_0_0_0 := v_0_0_0_0.Args[0]
+		if v_0_0_0_0_0.Op != OpRsh32x64 {
+			break
+		}
+		if v_0_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0_0.Args[1]
+		if n != v_0_0_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_0_0_1 := v_0_0_0_0_0.Args[1]
+		if v_0_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_0_0_1.AuxInt != 31 {
+			break
+		}
+		v_0_0_0_0_1 := v_0_0_0_0.Args[1]
+		if v_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_0_1.AuxInt
+		if n != v_0_0_0.Args[1] {
+			break
+		}
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 31 && kbar == 32-k) {
+			break
+		}
+		v.reset(OpEq32)
+		v0 := b.NewValue0(v.Pos, OpAnd32, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst32, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst32, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq32 s:(Sub32 x y) (Const32 [0]))
 	// cond: s.Uses == 1
 	// result: (Eq32 x y)
 	for {
@@ -9280,6 +10048,7 @@ func rewriteValuegeneric_OpEq32F_0(v *Value) bool {
 }
 func rewriteValuegeneric_OpEq64_0(v *Value) bool {
 	b := v.Block
+	typ := &b.Func.Config.Types
 	// match: (Eq64 x x)
 	// cond:
 	// result: (ConstBool [1])
@@ -9456,6 +10225,389 @@ func rewriteValuegeneric_OpEq64_0(v *Value) bool {
 		v.AuxInt = b2i(c == d)
 		return true
 	}
+	// match: (Eq64 n (Lsh64x64 (Rsh64x64 (Add64 <t> n (Rsh64Ux64 <t> (Rsh64x64 <t> n (Const64 <typ.UInt64> [63])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 63 && kbar == 64 - k
+	// result: (Eq64 (And64 <t> n (Const64 <t> [int64(1<<uint(k)-1)])) (Const64 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh64x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh64x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd64 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		if n != v_1_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_1 := v_1_0_0.Args[1]
+		if v_1_0_0_1.Op != OpRsh64Ux64 {
+			break
+		}
+		if v_1_0_0_1.Type != t {
+			break
+		}
+		_ = v_1_0_0_1.Args[1]
+		v_1_0_0_1_0 := v_1_0_0_1.Args[0]
+		if v_1_0_0_1_0.Op != OpRsh64x64 {
+			break
+		}
+		if v_1_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_1_0.Args[1]
+		if n != v_1_0_0_1_0.Args[0] {
+			break
+		}
+		v_1_0_0_1_0_1 := v_1_0_0_1_0.Args[1]
+		if v_1_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_1_0_1.AuxInt != 63 {
+			break
+		}
+		v_1_0_0_1_1 := v_1_0_0_1.Args[1]
+		if v_1_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_1_1.AuxInt
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 63 && kbar == 64-k) {
+			break
+		}
+		v.reset(OpEq64)
+		v0 := b.NewValue0(v.Pos, OpAnd64, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst64, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst64, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq64 n (Lsh64x64 (Rsh64x64 (Add64 <t> (Rsh64Ux64 <t> (Rsh64x64 <t> n (Const64 <typ.UInt64> [63])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 63 && kbar == 64 - k
+	// result: (Eq64 (And64 <t> n (Const64 <t> [int64(1<<uint(k)-1)])) (Const64 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh64x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh64x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd64 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		v_1_0_0_0 := v_1_0_0.Args[0]
+		if v_1_0_0_0.Op != OpRsh64Ux64 {
+			break
+		}
+		if v_1_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0.Args[1]
+		v_1_0_0_0_0 := v_1_0_0_0.Args[0]
+		if v_1_0_0_0_0.Op != OpRsh64x64 {
+			break
+		}
+		if v_1_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0_0.Args[1]
+		if n != v_1_0_0_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_0_0_1 := v_1_0_0_0_0.Args[1]
+		if v_1_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_0_0_1.AuxInt != 63 {
+			break
+		}
+		v_1_0_0_0_1 := v_1_0_0_0.Args[1]
+		if v_1_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_0_1.AuxInt
+		if n != v_1_0_0.Args[1] {
+			break
+		}
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 63 && kbar == 64-k) {
+			break
+		}
+		v.reset(OpEq64)
+		v0 := b.NewValue0(v.Pos, OpAnd64, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst64, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst64, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq64 (Lsh64x64 (Rsh64x64 (Add64 <t> n (Rsh64Ux64 <t> (Rsh64x64 <t> n (Const64 <typ.UInt64> [63])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 63 && kbar == 64 - k
+	// result: (Eq64 (And64 <t> n (Const64 <t> [int64(1<<uint(k)-1)])) (Const64 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh64x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh64x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd64 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		if n != v_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_1 := v_0_0_0.Args[1]
+		if v_0_0_0_1.Op != OpRsh64Ux64 {
+			break
+		}
+		if v_0_0_0_1.Type != t {
+			break
+		}
+		_ = v_0_0_0_1.Args[1]
+		v_0_0_0_1_0 := v_0_0_0_1.Args[0]
+		if v_0_0_0_1_0.Op != OpRsh64x64 {
+			break
+		}
+		if v_0_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_1_0.Args[1]
+		if n != v_0_0_0_1_0.Args[0] {
+			break
+		}
+		v_0_0_0_1_0_1 := v_0_0_0_1_0.Args[1]
+		if v_0_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_1_0_1.AuxInt != 63 {
+			break
+		}
+		v_0_0_0_1_1 := v_0_0_0_1.Args[1]
+		if v_0_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_1_1.AuxInt
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 63 && kbar == 64-k) {
+			break
+		}
+		v.reset(OpEq64)
+		v0 := b.NewValue0(v.Pos, OpAnd64, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst64, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst64, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	return false
+}
+func rewriteValuegeneric_OpEq64_10(v *Value) bool {
+	b := v.Block
+	typ := &b.Func.Config.Types
+	// match: (Eq64 (Lsh64x64 (Rsh64x64 (Add64 <t> (Rsh64Ux64 <t> (Rsh64x64 <t> n (Const64 <typ.UInt64> [63])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 63 && kbar == 64 - k
+	// result: (Eq64 (And64 <t> n (Const64 <t> [int64(1<<uint(k)-1)])) (Const64 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh64x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh64x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd64 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		v_0_0_0_0 := v_0_0_0.Args[0]
+		if v_0_0_0_0.Op != OpRsh64Ux64 {
+			break
+		}
+		if v_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0.Args[1]
+		v_0_0_0_0_0 := v_0_0_0_0.Args[0]
+		if v_0_0_0_0_0.Op != OpRsh64x64 {
+			break
+		}
+		if v_0_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0_0.Args[1]
+		if n != v_0_0_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_0_0_1 := v_0_0_0_0_0.Args[1]
+		if v_0_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_0_0_1.AuxInt != 63 {
+			break
+		}
+		v_0_0_0_0_1 := v_0_0_0_0.Args[1]
+		if v_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_0_1.AuxInt
+		if n != v_0_0_0.Args[1] {
+			break
+		}
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 63 && kbar == 64-k) {
+			break
+		}
+		v.reset(OpEq64)
+		v0 := b.NewValue0(v.Pos, OpAnd64, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst64, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst64, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
 	// match: (Eq64 s:(Sub64 x y) (Const64 [0]))
 	// cond: s.Uses == 1
 	// result: (Eq64 x y)
@@ -9553,6 +10705,7 @@ func rewriteValuegeneric_OpEq64F_0(v *Value) bool {
 }
 func rewriteValuegeneric_OpEq8_0(v *Value) bool {
 	b := v.Block
+	typ := &b.Func.Config.Types
 	// match: (Eq8 x x)
 	// cond:
 	// result: (ConstBool [1])
@@ -9729,6 +10882,389 @@ func rewriteValuegeneric_OpEq8_0(v *Value) bool {
 		v.AuxInt = b2i(c == d)
 		return true
 	}
+	// match: (Eq8 n (Lsh8x64 (Rsh8x64 (Add8 <t> n (Rsh8Ux64 <t> (Rsh8x64 <t> n (Const64 <typ.UInt64> [ 7])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 7 && kbar == 8 - k
+	// result: (Eq8 (And8 <t> n (Const8 <t> [int64(1<<uint(k)-1)])) (Const8 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh8x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh8x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd8 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		if n != v_1_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_1 := v_1_0_0.Args[1]
+		if v_1_0_0_1.Op != OpRsh8Ux64 {
+			break
+		}
+		if v_1_0_0_1.Type != t {
+			break
+		}
+		_ = v_1_0_0_1.Args[1]
+		v_1_0_0_1_0 := v_1_0_0_1.Args[0]
+		if v_1_0_0_1_0.Op != OpRsh8x64 {
+			break
+		}
+		if v_1_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_1_0.Args[1]
+		if n != v_1_0_0_1_0.Args[0] {
+			break
+		}
+		v_1_0_0_1_0_1 := v_1_0_0_1_0.Args[1]
+		if v_1_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_1_0_1.AuxInt != 7 {
+			break
+		}
+		v_1_0_0_1_1 := v_1_0_0_1.Args[1]
+		if v_1_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_1_1.AuxInt
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 7 && kbar == 8-k) {
+			break
+		}
+		v.reset(OpEq8)
+		v0 := b.NewValue0(v.Pos, OpAnd8, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst8, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst8, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq8 n (Lsh8x64 (Rsh8x64 (Add8 <t> (Rsh8Ux64 <t> (Rsh8x64 <t> n (Const64 <typ.UInt64> [ 7])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])))
+	// cond: k > 0 && k < 7 && kbar == 8 - k
+	// result: (Eq8 (And8 <t> n (Const8 <t> [int64(1<<uint(k)-1)])) (Const8 <t> [0]))
+	for {
+		_ = v.Args[1]
+		n := v.Args[0]
+		v_1 := v.Args[1]
+		if v_1.Op != OpLsh8x64 {
+			break
+		}
+		_ = v_1.Args[1]
+		v_1_0 := v_1.Args[0]
+		if v_1_0.Op != OpRsh8x64 {
+			break
+		}
+		_ = v_1_0.Args[1]
+		v_1_0_0 := v_1_0.Args[0]
+		if v_1_0_0.Op != OpAdd8 {
+			break
+		}
+		t := v_1_0_0.Type
+		_ = v_1_0_0.Args[1]
+		v_1_0_0_0 := v_1_0_0.Args[0]
+		if v_1_0_0_0.Op != OpRsh8Ux64 {
+			break
+		}
+		if v_1_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0.Args[1]
+		v_1_0_0_0_0 := v_1_0_0_0.Args[0]
+		if v_1_0_0_0_0.Op != OpRsh8x64 {
+			break
+		}
+		if v_1_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_1_0_0_0_0.Args[1]
+		if n != v_1_0_0_0_0.Args[0] {
+			break
+		}
+		v_1_0_0_0_0_1 := v_1_0_0_0_0.Args[1]
+		if v_1_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_0_0_0_0_1.AuxInt != 7 {
+			break
+		}
+		v_1_0_0_0_1 := v_1_0_0_0.Args[1]
+		if v_1_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_1_0_0_0_1.AuxInt
+		if n != v_1_0_0.Args[1] {
+			break
+		}
+		v_1_0_1 := v_1_0.Args[1]
+		if v_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_1_0_1.AuxInt
+		v_1_1 := v_1.Args[1]
+		if v_1_1.Op != OpConst64 {
+			break
+		}
+		if v_1_1.Type != typ.UInt64 {
+			break
+		}
+		if v_1_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 7 && kbar == 8-k) {
+			break
+		}
+		v.reset(OpEq8)
+		v0 := b.NewValue0(v.Pos, OpAnd8, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst8, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst8, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	// match: (Eq8 (Lsh8x64 (Rsh8x64 (Add8 <t> n (Rsh8Ux64 <t> (Rsh8x64 <t> n (Const64 <typ.UInt64> [ 7])) (Const64 <typ.UInt64> [kbar]))) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 7 && kbar == 8 - k
+	// result: (Eq8 (And8 <t> n (Const8 <t> [int64(1<<uint(k)-1)])) (Const8 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh8x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh8x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd8 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		if n != v_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_1 := v_0_0_0.Args[1]
+		if v_0_0_0_1.Op != OpRsh8Ux64 {
+			break
+		}
+		if v_0_0_0_1.Type != t {
+			break
+		}
+		_ = v_0_0_0_1.Args[1]
+		v_0_0_0_1_0 := v_0_0_0_1.Args[0]
+		if v_0_0_0_1_0.Op != OpRsh8x64 {
+			break
+		}
+		if v_0_0_0_1_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_1_0.Args[1]
+		if n != v_0_0_0_1_0.Args[0] {
+			break
+		}
+		v_0_0_0_1_0_1 := v_0_0_0_1_0.Args[1]
+		if v_0_0_0_1_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_1_0_1.AuxInt != 7 {
+			break
+		}
+		v_0_0_0_1_1 := v_0_0_0_1.Args[1]
+		if v_0_0_0_1_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_1_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_1_1.AuxInt
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 7 && kbar == 8-k) {
+			break
+		}
+		v.reset(OpEq8)
+		v0 := b.NewValue0(v.Pos, OpAnd8, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst8, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst8, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
+	return false
+}
+func rewriteValuegeneric_OpEq8_10(v *Value) bool {
+	b := v.Block
+	typ := &b.Func.Config.Types
+	// match: (Eq8 (Lsh8x64 (Rsh8x64 (Add8 <t> (Rsh8Ux64 <t> (Rsh8x64 <t> n (Const64 <typ.UInt64> [ 7])) (Const64 <typ.UInt64> [kbar])) n) (Const64 <typ.UInt64> [k])) (Const64 <typ.UInt64> [k])) n)
+	// cond: k > 0 && k < 7 && kbar == 8 - k
+	// result: (Eq8 (And8 <t> n (Const8 <t> [int64(1<<uint(k)-1)])) (Const8 <t> [0]))
+	for {
+		n := v.Args[1]
+		v_0 := v.Args[0]
+		if v_0.Op != OpLsh8x64 {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpRsh8x64 {
+			break
+		}
+		_ = v_0_0.Args[1]
+		v_0_0_0 := v_0_0.Args[0]
+		if v_0_0_0.Op != OpAdd8 {
+			break
+		}
+		t := v_0_0_0.Type
+		_ = v_0_0_0.Args[1]
+		v_0_0_0_0 := v_0_0_0.Args[0]
+		if v_0_0_0_0.Op != OpRsh8Ux64 {
+			break
+		}
+		if v_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0.Args[1]
+		v_0_0_0_0_0 := v_0_0_0_0.Args[0]
+		if v_0_0_0_0_0.Op != OpRsh8x64 {
+			break
+		}
+		if v_0_0_0_0_0.Type != t {
+			break
+		}
+		_ = v_0_0_0_0_0.Args[1]
+		if n != v_0_0_0_0_0.Args[0] {
+			break
+		}
+		v_0_0_0_0_0_1 := v_0_0_0_0_0.Args[1]
+		if v_0_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_0_0_0_0_1.AuxInt != 7 {
+			break
+		}
+		v_0_0_0_0_1 := v_0_0_0_0.Args[1]
+		if v_0_0_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		kbar := v_0_0_0_0_1.AuxInt
+		if n != v_0_0_0.Args[1] {
+			break
+		}
+		v_0_0_1 := v_0_0.Args[1]
+		if v_0_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_0_1.Type != typ.UInt64 {
+			break
+		}
+		k := v_0_0_1.AuxInt
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpConst64 {
+			break
+		}
+		if v_0_1.Type != typ.UInt64 {
+			break
+		}
+		if v_0_1.AuxInt != k {
+			break
+		}
+		if !(k > 0 && k < 7 && kbar == 8-k) {
+			break
+		}
+		v.reset(OpEq8)
+		v0 := b.NewValue0(v.Pos, OpAnd8, t)
+		v0.AddArg(n)
+		v1 := b.NewValue0(v.Pos, OpConst8, t)
+		v1.AuxInt = int64(1<<uint(k) - 1)
+		v0.AddArg(v1)
+		v.AddArg(v0)
+		v2 := b.NewValue0(v.Pos, OpConst8, t)
+		v2.AuxInt = 0
+		v.AddArg(v2)
+		return true
+	}
 	// match: (Eq8 s:(Sub8 x y) (Const8 [0]))
 	// cond: s.Uses == 1
 	// result: (Eq8 x y)
diff --git a/src/cmd/compile/internal/test/divconst_test.go b/src/cmd/compile/internal/test/divconst_test.go
index f585a5b51f8473..6b0bc4a6fbadc0 100644
--- a/src/cmd/compile/internal/test/divconst_test.go
+++ b/src/cmd/compile/internal/test/divconst_test.go
@@ -8,6 +8,8 @@ import (
 	"testing"
 )
 
+var boolres bool
+
 var i64res int64
 
 func BenchmarkDivconstI64(b *testing.B) {
@@ -16,6 +18,12 @@ func BenchmarkDivconstI64(b *testing.B) {
 	}
 }
 
+func BenchmarkDivisiblePow2constI64(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		boolres = int64(i)%16 == 0
+	}
+}
+
 var u64res uint64
 
 func BenchmarkDivconstU64(b *testing.B) {
@@ -32,6 +40,12 @@ func BenchmarkDivconstI32(b *testing.B) {
 	}
 }
 
+func BenchmarkDivisiblePow2constI32(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		boolres = int32(i)%16 == 0
+	}
+}
+
 var u32res uint32
 
 func BenchmarkDivconstU32(b *testing.B) {
@@ -48,6 +62,12 @@ func BenchmarkDivconstI16(b *testing.B) {
 	}
 }
 
+func BenchmarkDivisiblePow2constI16(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		boolres = int16(i)%16 == 0
+	}
+}
+
 var u16res uint16
 
 func BenchmarkDivconstU16(b *testing.B) {
@@ -64,6 +84,12 @@ func BenchmarkDivconstI8(b *testing.B) {
 	}
 }
 
+func BenchmarkDivisiblePow2constI8(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		boolres = int8(i)%16 == 0
+	}
+}
+
 var u8res uint8
 
 func BenchmarkDivconstU8(b *testing.B) {
diff --git a/test/codegen/arithmetic.go b/test/codegen/arithmetic.go
index b5976be9d258e6..a937be7fe5bfb3 100644
--- a/test/codegen/arithmetic.go
+++ b/test/codegen/arithmetic.go
@@ -176,15 +176,28 @@ func Pow2Mods(n1 uint, n2 int) (uint, int) {
 	// ppc64le:"ANDCC\t[$]31"
 	a := n1 % 32 // unsigned
 
-	// 386:-"IDIVL"
-	// amd64:-"IDIVQ"
-	// arm:-".*udiv"
-	// arm64:-"REM"
+	// 386:"SHRL",-"IDIVL"
+	// amd64:"SHRQ",-"IDIVQ"
+	// arm:"SRA",-".*udiv"
+	// arm64:"ASR",-"REM"
+	// ppc64:"SRAD"
+	// ppc64le:"SRAD"
 	b := n2 % 64 // signed
 
 	return a, b
 }
 
+// Check that signed divisibility checks get converted to AND on low bits
+func Pow2DivisibleSigned(n int) bool {
+	// 386:"TESTL\t[$]63",-"DIVL",-"SHRL"
+	// amd64:"TESTQ\t[$]63",-"DIVQ",-"SHRQ"
+	// arm:"AND\t[$]63",-".*udiv",-"SRA"
+	// arm64:"AND\t[$]63",-"UDIV",-"ASR"
+	// ppc64:"ANDCC\t[$]63",-"SRAD"
+	// ppc64le:"ANDCC\t[$]63",-"SRAD"
+	return n%64 == 0 // signed
+}
+
 // Check that constant modulo divs get turned into MULs
 func ConstMods(n1 uint, n2 int) (uint, int) {
 	// amd64:"MOVQ\t[$]-1085102592571150095","MULQ",-"DIVQ"