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[InstCombine] ror/rol(X, RotAmt) == C --> X == rol/ror(C, RotAmt) (PR51567) 

```
----------------------------------------
define i1 @src(i32 %0) {
%1:
  %2 = fshl i32 %0, i32 %0, i32 25
  %3 = icmp eq i32 %2, 5
  ret i1 %3
}
=>
define i1 @tgt(i32 %0) {
%1:
  %2 = icmp eq i32 %0, 640
  ret i1 %2
}
Transformation seems to be correct!
```

https://alive2.llvm.org/ce/z/GdY8Jm

Solves PR51567

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D109283
This commit is contained in:
Dávid Bolvanský 2021-09-07 18:04:38 +02:00
parent 81d3ac0cf2
commit 3b5f318f5d
2 changed files with 21 additions and 16 deletions
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20
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -3228,12 +3228,22 @@ Instruction *InstCombinerImpl::foldICmpEqIntrinsicWithConstant(
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))
if (II->getArgOperand(0) == II->getArgOperand(1)) {
// (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())
return new ICmpInst(Pred, II->getArgOperand(0), Cmp.getOperand(1));
const APInt *RotAmtC;
// ror(X, RotAmtC) == C --> X == rol(C, RotAmtC)
// rol(X, RotAmtC) == C --> X == ror(C, RotAmtC)
if (match(II->getArgOperand(2), m_APInt(RotAmtC)))
return new ICmpInst(Pred, II->getArgOperand(0),
II->getIntrinsicID() == Intrinsic::fshl
? ConstantInt::get(Ty, C.rotr(*RotAmtC))
: ConstantInt::get(Ty, C.rotl(*RotAmtC)));
}
break;
case Intrinsic::uadd_sat: {

17
llvm/test/Transforms/InstCombine/icmp-rotate.ll
View File

@ -108,8 +108,7 @@ define <2 x i1> @ror_eq_vec(<2 x i5> %x, <2 x i5> %y, <2 x i5> %z) {
define i1 @rol_eq_cst(i8 %x) {
; CHECK-LABEL: @rol_eq_cst(
; CHECK-NEXT: [[F:%.*]] = tail call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 3)
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[F]], 2
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X:%.*]], 64
; CHECK-NEXT: ret i1 [[R]]
;
%f = tail call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 3)
@ -119,8 +118,7 @@ define i1 @rol_eq_cst(i8 %x) {
define i1 @rol_ne_cst(i8 %x) {
; CHECK-LABEL: @rol_ne_cst(
; CHECK-NEXT: [[F:%.*]] = tail call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 3)
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[F]], 2
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X:%.*]], 64
; CHECK-NEXT: ret i1 [[R]]
;
%f = tail call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 3)
@ -132,7 +130,7 @@ define i1 @rol_eq_cst_use(i8 %x) {
; CHECK-LABEL: @rol_eq_cst_use(
; CHECK-NEXT: [[F:%.*]] = tail call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 3)
; CHECK-NEXT: call void @use(i8 [[F]])
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[F]], 2
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X]], 64
; CHECK-NEXT: ret i1 [[R]]
;
%f = tail call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 3)
@ -143,8 +141,7 @@ define i1 @rol_eq_cst_use(i8 %x) {
define i1 @ror_eq_cst(i8 %x) {
; CHECK-LABEL: @ror_eq_cst(
; CHECK-NEXT: [[F:%.*]] = call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 6)
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[F]], 3
; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X:%.*]], 12
; CHECK-NEXT: ret i1 [[R]]
;
%f = tail call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 2)
@ -154,8 +151,7 @@ define i1 @ror_eq_cst(i8 %x) {
define i1 @ror_ne_cst(i8 %x) {
; CHECK-LABEL: @ror_ne_cst(
; CHECK-NEXT: [[F:%.*]] = call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 6)
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[F]], 3
; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X:%.*]], 12
; CHECK-NEXT: ret i1 [[R]]
;
%f = tail call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 2)
@ -165,8 +161,7 @@ define i1 @ror_ne_cst(i8 %x) {
define <2 x i1> @rol_eq_cst_vec(<2 x i5> %x) {
; CHECK-LABEL: @rol_eq_cst_vec(
; CHECK-NEXT: [[F:%.*]] = tail call <2 x i5> @llvm.fshl.v2i5(<2 x i5> [[X:%.*]], <2 x i5> [[X]], <2 x i5> <i5 3, i5 3>)
; CHECK-NEXT: [[R:%.*]] = icmp eq <2 x i5> [[F]], <i5 2, i5 2>
; CHECK-NEXT: [[R:%.*]] = icmp eq <2 x i5> [[X:%.*]], <i5 8, i5 8>
; CHECK-NEXT: ret <2 x i1> [[R]]
;
%f = tail call <2 x i5> @llvm.fshl.v2i5(<2 x i5> %x, <2 x i5> %x, <2 x i5> <i5 3, i5 3>)