[PATCH] D152348: [InstCombine] Canonicalize (icmp eq/ne X, rotate(X)) to always use rotate-left
Noah Goldstein via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 7 01:15:38 PDT 2023
goldstein.w.n created this revision.
goldstein.w.n added reviewers: nikic, spatel.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
goldstein.w.n requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.
We canonicalize rotate-right -> rotate-left in other places. Makes
sense to do so here as well.
Proof: https://alive2.llvm.org/ce/z/HL3TpK
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D152348
Files:
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/test/Transforms/InstCombine/icmp-equality-rotate.ll
Index: llvm/test/Transforms/InstCombine/icmp-equality-rotate.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp-equality-rotate.ll
+++ llvm/test/Transforms/InstCombine/icmp-equality-rotate.ll
@@ -30,9 +30,9 @@
define i1 @cmpne_rorr_rorr(i8 %x, i8 %C0, i8 %C1) {
; CHECK-LABEL: @cmpne_rorr_rorr(
-; CHECK-NEXT: [[X_RORR0:%.*]] = call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[C0:%.*]])
-; CHECK-NEXT: [[X_RORR1:%.*]] = call i8 @llvm.fshr.i8(i8 [[X]], i8 [[X]], i8 [[C1:%.*]])
-; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[X_RORR0]], [[X_RORR1]]
+; CHECK-NEXT: [[TMP1:%.*]] = sub i8 [[C0:%.*]], [[C1:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = call i8 @llvm.fshr.i8(i8 [[X:%.*]], i8 [[X]], i8 [[TMP1]])
+; CHECK-NEXT: [[R:%.*]] = icmp ne i8 [[TMP2]], [[X]]
; CHECK-NEXT: ret i1 [[R]]
;
%x_rorr0 = call i8 @llvm.fshr.i8(i8 %x, i8 %x, i8 %C0)
@@ -71,10 +71,10 @@
define i1 @cmpeq_rorlC_rorlC_multiuse1(i8 %x, i8 %C0) {
; CHECK-LABEL: @cmpeq_rorlC_rorlC_multiuse1(
-; CHECK-NEXT: [[X_RORL0:%.*]] = call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 6)
-; CHECK-NEXT: [[X_RORL1:%.*]] = call i8 @llvm.fshl.i8(i8 [[X]], i8 [[X]], i8 3)
+; CHECK-NEXT: [[X_RORL1:%.*]] = call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[X]], i8 3)
; CHECK-NEXT: call void @use.i8(i8 [[X_RORL1]])
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[X_RORL0]], [[X_RORL1]]
+; CHECK-NEXT: [[TMP1:%.*]] = call i8 @llvm.fshl.i8(i8 [[X]], i8 [[X]], i8 3)
+; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[TMP1]], [[X]]
; CHECK-NEXT: ret i1 [[R]]
;
%x_rorl0 = call i8 @llvm.fshl.i8(i8 %x, i8 %x, i8 6)
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3443,7 +3443,9 @@
}
/// Fold an icmp with LLVM intrinsics
-static Instruction *foldICmpIntrinsicWithIntrinsic(ICmpInst &Cmp) {
+static Instruction *
+foldICmpIntrinsicWithIntrinsic(ICmpInst &Cmp,
+ InstCombiner::BuilderTy &Builder) {
assert(Cmp.isEquality());
ICmpInst::Predicate Pred = Cmp.getPredicate();
@@ -3468,9 +3470,30 @@
break;
if (IIOp1->getOperand(0) != IIOp1->getOperand(1))
break;
- if (IIOp0->getOperand(2) != IIOp1->getOperand(2))
- break;
- return new ICmpInst(Pred, IIOp0->getOperand(0), IIOp1->getOperand(0));
+ if (IIOp0->getOperand(2) == IIOp1->getOperand(2))
+ return new ICmpInst(Pred, IIOp0->getOperand(0), IIOp1->getOperand(0));
+
+ // rotate(X, Amt0) == rotate(X, Amt1)
+ // -> rotate(X, Amt0 - Amt1) == X
+ // Do this if either both rotates have one use or if only one has one use
+ // and Amt0/Amt1 are constants.
+ if (IIOp0->getOperand(0) == IIOp1->getOperand(0)) {
+ unsigned OneUses = IIOp0->hasOneUse() + IIOp1->hasOneUse();
+ if (OneUses == 2 ||
+ (OneUses == 1 && match(IIOp0->getOperand(2), m_ImmConstant()) &&
+ match(IIOp1->getOperand(2), m_ImmConstant()))) {
+ Module *Mod = Cmp.getModule();
+ Function *Rotate = Intrinsic::getDeclaration(
+ Mod, IIOp0->getIntrinsicID(), Op0->getType());
+ Value *SubAmt =
+ Builder.CreateSub(IIOp0->getOperand(2), IIOp1->getOperand(2));
+ return new ICmpInst(
+ Pred, IIOp0->getOperand(0),
+ Builder.CreateCall(
+ Rotate, {IIOp0->getOperand(0), IIOp0->getOperand(0), SubAmt}));
+ }
+ }
+ break;
default:
break;
}
@@ -4970,7 +4993,7 @@
}
}
- if (Instruction *ICmp = foldICmpIntrinsicWithIntrinsic(I))
+ if (Instruction *ICmp = foldICmpIntrinsicWithIntrinsic(I, Builder))
return ICmp;
// Canonicalize checking for a power-of-2-or-zero value:
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