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[InstCombine] fold (rotate X) eq/ne (0/-1) 

This generalizes the examples shown in:
https://llvm.org/PR51566

https://alive2.llvm.org/ce/z/V-sEy9
This commit is contained in:
Sanjay Patel 2021-09-03 14:35:10 -04:00
parent d1458903eb
commit fd807601a7
2 changed files with 30 additions and 14 deletions
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10
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -3226,6 +3226,16 @@ Instruction *InstCombinerImpl::foldICmpEqIntrinsicWithConstant(
break;
}
case Intrinsic::fshl:
case Intrinsic::fshr:
// (rot X, ?) == 0/-1 --> X == 0/-1
// TODO: This transform is safe to re-use undef elts in a vector, but
// the constant value passed in by the caller doesn't allow that.
if (C.isNullValue() || C.isAllOnesValue())
if (II->getArgOperand(0) == II->getArgOperand(1))
return new ICmpInst(Pred, II->getArgOperand(0), Cmp.getOperand(1));
break;
case Intrinsic::uadd_sat: {
// uadd.sat(a, b) == 0 -> (a | b) == 0
if (C.isNullValue()) {

34
llvm/test/Transforms/InstCombine/icmp-fsh.ll
View File

@ -8,8 +8,7 @@ declare void @use(i8)
define i1 @rotl_eq_0(i8 %x, i8 %y) {
; CHECK-LABEL: @rotl_eq_0(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[ROT]], 0
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X:%.*]], 0
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 %y)
@ -17,11 +16,13 @@ define i1 @rotl_eq_0(i8 %x, i8 %y) {
ret i1 %r
}
; Extra use is ok.
define i1 @rotl_ne_0(i8 %x, i8 %y) {
; CHECK-LABEL: @rotl_ne_0(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: call void @use(i8 [[ROT]])
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[ROT]], 0
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X]], 0
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 %y)
@ -32,8 +33,7 @@ define i1 @rotl_ne_0(i8 %x, i8 %y) {
define i1 @rotl_eq_n1(i8 %x, i8 %y) {
; CHECK-LABEL: @rotl_eq_n1(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[ROT]], -1
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X:%.*]], -1
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 %y)
@ -41,10 +41,11 @@ define i1 @rotl_eq_n1(i8 %x, i8 %y) {
ret i1 %r
}
; Vectors work too.
define <2 x i1> @rotl_ne_n1(<2 x i5> %x, <2 x i5> %y) {
; CHECK-LABEL: @rotl_ne_n1(
; CHECK-NEXT: [[ROT:%.*]] = tail call <2 x i5> @llvm.fshl.v2i5(<2 x i5> [[X:%.*]], <2 x i5> [[X]], <2 x i5> [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = icmp ne <2 x i5> [[ROT]], <i5 -1, i5 -1>
; CHECK-NEXT: [[R:%.*]] = icmp ne <2 x i5> [[X:%.*]], <i5 -1, i5 -1>
; CHECK-NEXT: ret <2 x i1> [[R]]
;
%rot = tail call <2 x i5> @llvm.fshl.v2i5(<2 x i5>%x, <2 x i5> %x, <2 x i5> %y)
@ -52,6 +53,8 @@ define <2 x i1> @rotl_ne_n1(<2 x i5> %x, <2 x i5> %y) {
ret <2 x i1> %r
}
; TODO: We filter out vector constants with undef elts, but that isn't needed for this transform.
define <2 x i1> @rotl_ne_n1_undef(<2 x i5> %x, <2 x i5> %y) {
; CHECK-LABEL: @rotl_ne_n1_undef(
; CHECK-NEXT: [[ROT:%.*]] = tail call <2 x i5> @llvm.fshl.v2i5(<2 x i5> [[X:%.*]], <2 x i5> [[X]], <2 x i5> [[Y:%.*]])
@ -67,7 +70,7 @@ define i1 @rotr_eq_0(i8 %x, i8 %y) {
; CHECK-LABEL: @rotr_eq_0(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: call void @use(i8 [[ROT]])
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[ROT]], 0
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X]], 0
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 %y)
@ -78,8 +81,7 @@ define i1 @rotr_eq_0(i8 %x, i8 %y) {
define i1 @rotr_ne_0(i8 %x, i8 %y) {
; CHECK-LABEL: @rotr_ne_0(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[ROT]], 0
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X:%.*]], 0
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 %y)
@ -89,8 +91,7 @@ define i1 @rotr_ne_0(i8 %x, i8 %y) {
define i1 @rotr_eq_n1(i8 %x, i8 %y) {
; CHECK-LABEL: @rotr_eq_n1(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[ROT]], -1
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X:%.*]], -1
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 %y)
@ -100,8 +101,7 @@ define i1 @rotr_eq_n1(i8 %x, i8 %y) {
define i1 @rotr_ne_n1(i8 %x, i8 %y) {
; CHECK-LABEL: @rotr_ne_n1(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[ROT]], -1
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X:%.*]], -1
; CHECK-NEXT: ret i1 [[R]]
;
%rot = tail call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 %y)
@ -109,6 +109,8 @@ define i1 @rotr_ne_n1(i8 %x, i8 %y) {
ret i1 %r
}
; negative test - wrong constant value
define i1 @rotr_ne_1(i8 %x, i8 %y) {
; CHECK-LABEL: @rotr_ne_1(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
@ -120,6 +122,8 @@ define i1 @rotr_ne_1(i8 %x, i8 %y) {
ret i1 %r
}
; negative test - wrong predicate
define i1 @rotr_sgt_n1(i8 %x, i8 %y) {
; CHECK-LABEL: @rotr_sgt_n1(
; CHECK-NEXT: [[ROT:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[Y:%.*]])
@ -131,6 +135,8 @@ define i1 @rotr_sgt_n1(i8 %x, i8 %y) {
ret i1 %r
}
; negative test - must be a rotate, not general funnel shift
define i1 @fshr_sgt_n1(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @fshr_sgt_n1(
; CHECK-NEXT: [[FSH:%.*]] = tail call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[Y:%.*]], i8 [[Z:%.*]])