egraphs: Remove iconcat as a shift input

cranelift/codegen/src/opts/shifts.isle

@@ -130,3 +130,17 @@
 (rule (simplify (rotl ty x (ireduce _ y @ (value_type (fits_in_64 _))))) (rotl ty x y))
 (rule (simplify (rotl ty x (uextend _ y))) (rotl ty x y))
 (rule (simplify (rotl ty x (sextend _ y))) (rotl ty x y))
+
+;; Remove iconcat from the shift amount input. This is correct even if the
+;; the iconcat is i8 type, since it can represent the largest shift amount
+;; for i128 types.
+;;
+;; (op x (iconcat y1 y2)) == (op x y1)
+;;
+;; where `op` is one of ishl, ushr, sshr, rotl, rotr
+
+(rule (simplify (ishl ty x (iconcat _ y _))) (ishl ty x y))
+(rule (simplify (ushr ty x (iconcat _ y _))) (ushr ty x y))
+(rule (simplify (sshr ty x (iconcat _ y _))) (sshr ty x y))
+(rule (simplify (rotr ty x (iconcat _ y _))) (rotr ty x y))
+(rule (simplify (rotl ty x (iconcat _ y _))) (rotl ty x y))

cranelift/filetests/filetests/egraph/shifts.clif

@@ -469,3 +469,58 @@ block0(v0: i8, v1: i16):
 
 ; check: v4 = rotl v0, v1
 ; check: return v4
+
+
+function %ishl_amt_type_iconcat(i8, i16, i16) -> i8 {
+block0(v0: i8, v1: i16, v2: i16):
+    v3 = iconcat.i16 v1, v2
+    v4 = ishl.i8 v0, v3
+    return v4
+}
+
+; check: v5 = ishl v0, v1
+; check: return v5
+
+
+function %ushr_amt_type_iconcat(i8, i16, i16) -> i8 {
+block0(v0: i8, v1: i16, v2: i16):
+    v3 = iconcat.i16 v1, v2
+    v4 = ushr.i8 v0, v3
+    return v4
+}
+
+; check: v5 = ushr v0, v1
+; check: return v5
+
+
+function %sshr_amt_type_iconcat(i8, i16, i16) -> i8 {
+block0(v0: i8, v1: i16, v2: i16):
+    v3 = iconcat.i16 v1, v2
+    v4 = sshr.i8 v0, v3
+    return v4
+}
+
+; check: v5 = sshr v0, v1
+; check: return v5
+
+
+function %rotr_amt_type_iconcat(i8, i16, i16) -> i8 {
+block0(v0: i8, v1: i16, v2: i16):
+    v3 = iconcat.i16 v1, v2
+    v4 = rotr.i8 v0, v3
+    return v4
+}
+
+; check: v5 = rotr v0, v1
+; check: return v5
+
+
+function %rotl_amt_type_iconcat(i8, i16, i16) -> i8 {
+block0(v0: i8, v1: i16, v2: i16):
+    v3 = iconcat.i16 v1, v2
+    v4 = rotl.i8 v0, v3
+    return v4
+}
+
+; check: v5 = rotl v0, v1
+; check: return v5