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[AArch64] Lower extending sitofp using tbl (llvm#92528)
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In a similar manner as in https://reviews.llvm.org/D133494
use `TBL` to place bytes in the *upper* part of `i32` elements
and then convert to float using fixed-point `scvtf`, i.e.

    scvtf Vd.4s, Vn.4s, #24
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@momchil-velikov
momchil-velikov authored Jun 17, 2024
1 parent 5914a56 commit d1a4f0c
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Showing 3 changed files with 313 additions and 3 deletions.
3 changes: 2 additions & 1 deletion llvm/lib/CodeGen/CodeGenPrepare.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8331,7 +8331,8 @@ bool CodeGenPrepare::optimizeInst(Instruction *I, ModifyDT &ModifiedDT) {
if (OptimizeNoopCopyExpression(CI, *TLI, *DL))
return true;

if ((isa<UIToFPInst>(I) || isa<FPToUIInst>(I) || isa<TruncInst>(I)) &&
if ((isa<UIToFPInst>(I) || isa<SIToFPInst>(I) || isa<FPToUIInst>(I) ||
isa<TruncInst>(I)) &&
TLI->optimizeExtendOrTruncateConversion(
I, LI->getLoopFor(I->getParent()), *TTI))
return true;
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37 changes: 35 additions & 2 deletions llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15869,6 +15869,24 @@ static Value *createTblShuffleForZExt(IRBuilderBase &Builder, Value *Op,
return Result;
}

static Value *createTblShuffleForSExt(IRBuilderBase &Builder, Value *Op,
FixedVectorType *DstTy,
bool IsLittleEndian) {
auto *SrcTy = cast<FixedVectorType>(Op->getType());
auto SrcWidth = cast<IntegerType>(SrcTy->getElementType())->getBitWidth();
auto DstWidth = cast<IntegerType>(DstTy->getElementType())->getBitWidth();

SmallVector<int> Mask;
if (!createTblShuffleMask(SrcWidth, DstWidth, SrcTy->getNumElements(),
!IsLittleEndian, Mask))
return nullptr;

auto *FirstEltZero = Builder.CreateInsertElement(
PoisonValue::get(SrcTy), Builder.getInt8(0), uint64_t(0));

return Builder.CreateShuffleVector(Op, FirstEltZero, Mask);
}

static void createTblForTrunc(TruncInst *TI, bool IsLittleEndian) {
IRBuilder<> Builder(TI);
SmallVector<Value *> Parts;
Expand Down Expand Up @@ -16049,14 +16067,29 @@ bool AArch64TargetLowering::optimizeExtendOrTruncateConversion(
Value *ZExt = createTblShuffleForZExt(
Builder, I->getOperand(0), FixedVectorType::getInteger(DstTy),
FixedVectorType::getInteger(DstTy), Subtarget->isLittleEndian());
if (!ZExt)
return false;
assert(ZExt && "Cannot fail for the i8 to float conversion");
auto *UI = Builder.CreateUIToFP(ZExt, DstTy);
I->replaceAllUsesWith(UI);
I->eraseFromParent();
return true;
}

auto *SIToFP = dyn_cast<SIToFPInst>(I);
if (SIToFP && SrcTy->getElementType()->isIntegerTy(8) &&
DstTy->getElementType()->isFloatTy()) {
IRBuilder<> Builder(I);
auto *Shuffle = createTblShuffleForSExt(Builder, I->getOperand(0),
FixedVectorType::getInteger(DstTy),
Subtarget->isLittleEndian());
assert(Shuffle && "Cannot fail for the i8 to float conversion");
auto *Cast = Builder.CreateBitCast(Shuffle, VectorType::getInteger(DstTy));
auto *AShr = Builder.CreateAShr(Cast, 24, "", true);
auto *SI = Builder.CreateSIToFP(AShr, DstTy);
I->replaceAllUsesWith(SI);
I->eraseFromParent();
return true;
}

// Convert 'fptoui <(8|16) x float> to <(8|16) x i8>' to a wide fptoui
// followed by a truncate lowered to using tbl.4.
auto *FPToUI = dyn_cast<FPToUIInst>(I);
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276 changes: 276 additions & 0 deletions llvm/test/CodeGen/AArch64/sitofp-to-tbl.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,276 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
; RUN: llc -verify-machineinstrs < %s | FileCheck %s

target triple = "aarch64-linux"

; CHECK-LABEL: .LCPI0_0:
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 4
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 5
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 6
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 7
; CHECK-NEXT: .LCPI0_1:
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 0
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 1
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 2
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 3

define void @sitofp_v8i8_to_v8f32(ptr %src, ptr %dst) {
; CHECK-LABEL: sitofp_v8i8_to_v8f32:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: adrp x8, .LCPI0_0
; CHECK-NEXT: adrp x9, .LCPI0_1
; CHECK-NEXT: ldr q0, [x8, :lo12:.LCPI0_0]
; CHECK-NEXT: ldr q1, [x9, :lo12:.LCPI0_1]
; CHECK-NEXT: mov x8, xzr
; CHECK-NEXT: .LBB0_1: // %loop
; CHECK-NEXT: // =>This Inner Loop Header: Depth=1
; CHECK-NEXT: ldr d2, [x0, x8, lsl #3]
; CHECK-NEXT: add x9, x1, x8, lsl #5
; CHECK-NEXT: add x8, x8, #1
; CHECK-NEXT: cmp x8, #1000
; CHECK-NEXT: tbl v3.16b, { v2.16b }, v0.16b
; CHECK-NEXT: tbl v2.16b, { v2.16b }, v1.16b
; CHECK-NEXT: scvtf v3.4s, v3.4s, #24
; CHECK-NEXT: scvtf v2.4s, v2.4s, #24
; CHECK-NEXT: stp q2, q3, [x9]
; CHECK-NEXT: b.eq .LBB0_1
; CHECK-NEXT: // %bb.2: // %exit
; CHECK-NEXT: ret
entry:
br label %loop

loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
%gep.src = getelementptr inbounds <8 x i8>, ptr %src, i64 %iv
%l = load <8 x i8>, ptr %gep.src
%conv = sitofp <8 x i8> %l to <8 x float>
%gep.dst = getelementptr inbounds <8 x float>, ptr %dst, i64 %iv
store <8 x float> %conv, ptr %gep.dst
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, 1000
br i1 %ec, label %loop, label %exit

exit:
ret void
}

; CHECK-LABEL: .LCPI1_0:
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 12
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 13
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 14
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 15
; CHECK-NEXT: .LCPI1_1:
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 8
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 9
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 10
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 11
; CHECK-NEXT: .LCPI1_2:
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 4
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 5
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 6
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 7
; CHECK-NEXT: .LCPI1_3:
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 0
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 1
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 2
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 255
; CHECK-NEXT: .byte 3

define void @sitofp_v16i8_to_v16f32(ptr %src, ptr %dst) {
; CHECK-LABEL: sitofp_v16i8_to_v16f32:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: adrp x8, .LCPI1_0
; CHECK-NEXT: adrp x9, .LCPI1_1
; CHECK-NEXT: adrp x10, .LCPI1_2
; CHECK-NEXT: ldr q0, [x8, :lo12:.LCPI1_0]
; CHECK-NEXT: adrp x8, .LCPI1_3
; CHECK-NEXT: ldr q1, [x9, :lo12:.LCPI1_1]
; CHECK-NEXT: ldr q2, [x10, :lo12:.LCPI1_2]
; CHECK-NEXT: ldr q3, [x8, :lo12:.LCPI1_3]
; CHECK-NEXT: mov x8, xzr
; CHECK-NEXT: .LBB1_1: // %loop
; CHECK-NEXT: // =>This Inner Loop Header: Depth=1
; CHECK-NEXT: ldr q4, [x0, x8, lsl #4]
; CHECK-NEXT: add x9, x1, x8, lsl #6
; CHECK-NEXT: add x8, x8, #1
; CHECK-NEXT: cmp x8, #1000
; CHECK-NEXT: tbl v5.16b, { v4.16b }, v0.16b
; CHECK-NEXT: tbl v6.16b, { v4.16b }, v1.16b
; CHECK-NEXT: tbl v7.16b, { v4.16b }, v2.16b
; CHECK-NEXT: tbl v4.16b, { v4.16b }, v3.16b
; CHECK-NEXT: scvtf v5.4s, v5.4s, #24
; CHECK-NEXT: scvtf v6.4s, v6.4s, #24
; CHECK-NEXT: scvtf v7.4s, v7.4s, #24
; CHECK-NEXT: scvtf v4.4s, v4.4s, #24
; CHECK-NEXT: stp q6, q5, [x9, #32]
; CHECK-NEXT: stp q4, q7, [x9]
; CHECK-NEXT: b.eq .LBB1_1
; CHECK-NEXT: // %bb.2: // %exit
; CHECK-NEXT: ret
entry:
br label %loop

loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
%gep.src = getelementptr inbounds <16 x i8>, ptr %src, i64 %iv
%l = load <16 x i8>, ptr %gep.src
%conv = sitofp <16 x i8> %l to <16 x float>
%gep.dst = getelementptr inbounds <16 x float>, ptr %dst, i64 %iv
store <16 x float> %conv, ptr %gep.dst
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, 1000
br i1 %ec, label %loop, label %exit

exit:
ret void
}


; Negative tests, currently we don't convert to f16/bf16 via `tbl`.
define void @sitofp_v8i8_to_v8f16(ptr %src, ptr %dst) {
; CHECK-LABEL: sitofp_v8i8_to_v8f16:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: mov x8, xzr
; CHECK-NEXT: .LBB2_1: // %loop
; CHECK-NEXT: // =>This Inner Loop Header: Depth=1
; CHECK-NEXT: ldr d0, [x0, x8, lsl #3]
; CHECK-NEXT: sshll v0.8h, v0.8b, #0
; CHECK-NEXT: sshll v1.4s, v0.4h, #0
; CHECK-NEXT: sshll2 v0.4s, v0.8h, #0
; CHECK-NEXT: scvtf v1.4s, v1.4s
; CHECK-NEXT: scvtf v0.4s, v0.4s
; CHECK-NEXT: fcvtn v1.4h, v1.4s
; CHECK-NEXT: fcvtn2 v1.8h, v0.4s
; CHECK-NEXT: str q1, [x1, x8, lsl #4]
; CHECK-NEXT: add x8, x8, #1
; CHECK-NEXT: cmp x8, #1000
; CHECK-NEXT: b.eq .LBB2_1
; CHECK-NEXT: // %bb.2: // %exit
; CHECK-NEXT: ret
entry:
br label %loop

loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
%gep.src = getelementptr inbounds <8 x i8>, ptr %src, i64 %iv
%l = load <8 x i8>, ptr %gep.src
%conv = sitofp <8 x i8> %l to <8 x half>
%gep.dst = getelementptr inbounds <8 x half>, ptr %dst, i64 %iv
store <8 x half> %conv, ptr %gep.dst
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, 1000
br i1 %ec, label %loop, label %exit

exit:
ret void
}


; Negative test, conversion to double with the help of `tbl` not implemented (TODO)
define void @sitofp_v2i8_to_v2f64(ptr %src, ptr %dst) {
; CHECK-LABEL: sitofp_v2i8_to_v2f64:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: mov x8, xzr
; CHECK-NEXT: .LBB3_1: // %loop
; CHECK-NEXT: // =>This Inner Loop Header: Depth=1
; CHECK-NEXT: add x9, x0, x8, lsl #1
; CHECK-NEXT: ldrsb w10, [x9]
; CHECK-NEXT: ldrsb w9, [x9, #1]
; CHECK-NEXT: fmov s0, w10
; CHECK-NEXT: mov v0.s[1], w9
; CHECK-NEXT: sshll v0.2d, v0.2s, #0
; CHECK-NEXT: scvtf v0.2d, v0.2d
; CHECK-NEXT: str q0, [x1, x8, lsl #4]
; CHECK-NEXT: add x8, x8, #1
; CHECK-NEXT: cmp x8, #1000
; CHECK-NEXT: b.eq .LBB3_1
; CHECK-NEXT: // %bb.2: // %exit
; CHECK-NEXT: ret
entry:
br label %loop

loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
%gep.src = getelementptr inbounds <2 x i8>, ptr %src, i64 %iv
%l = load <2 x i8>, ptr %gep.src
%conv = sitofp <2 x i8> %l to <2 x double>
%gep.dst = getelementptr inbounds <2 x double>, ptr %dst, i64 %iv
store <2 x double> %conv, ptr %gep.dst
%iv.next = add i64 %iv, 1
%ec = icmp eq i64 %iv.next, 1000
br i1 %ec, label %loop, label %exit

exit:
ret void
}

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