[llvm] r315857 - revert r314984: revert r314698 - [InstCombine] remove one-use restriction for icmp (shr exact X, C1), C2 --> icmp X, (C2<<C1)
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 15 08:39:15 PDT 2017
Author: spatel
Date: Sun Oct 15 08:39:15 2017
New Revision: 315857
URL: http://llvm.org/viewvc/llvm-project?rev=315857&view=rev
Log:
revert r314984: revert r314698 - [InstCombine] remove one-use restriction for icmp (shr exact X, C1), C2 --> icmp X, (C2<<C1)
Recommitting r314698. The bug exposed by this change should be fixed with:
https://reviews.llvm.org/rL315579
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/icmp-shr.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=315857&r1=315856&r2=315857&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Sun Oct 15 08:39:15 2017
@@ -2060,15 +2060,15 @@ Instruction *InstCombiner::foldICmpShrCo
(!IsAShr && C.shl(ShAmtVal).lshr(ShAmtVal) == C)) &&
"Expected icmp+shr simplify did not occur.");
- // Check if the bits shifted out are known to be zero. If so, we can compare
- // against the unshifted value:
+ // If the bits shifted out are known zero, compare the unshifted value:
// (X & 4) >> 1 == 2 --> (X & 4) == 4.
Constant *ShiftedCmpRHS = ConstantInt::get(ShrTy, C << ShAmtVal);
- if (Shr->hasOneUse()) {
- if (Shr->isExact())
- return new ICmpInst(Pred, X, ShiftedCmpRHS);
+ if (Shr->isExact())
+ return new ICmpInst(Pred, X, ShiftedCmpRHS);
- // Otherwise strength reduce the shift into an 'and'.
+ if (Shr->hasOneUse()) {
+ // Canonicalize the shift into an 'and':
+ // icmp eq/ne (shr X, ShAmt), C --> icmp eq/ne (and X, HiMask), (C << ShAmt)
APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
Constant *Mask = ConstantInt::get(ShrTy, Val);
Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
Modified: llvm/trunk/test/Transforms/InstCombine/icmp-shr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp-shr.ll?rev=315857&r1=315856&r2=315857&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp-shr.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp-shr.ll Sun Oct 15 08:39:15 2017
@@ -483,7 +483,7 @@ declare void @foo(i32)
define i1 @exact_multiuse(i32 %x) {
; CHECK-LABEL: @exact_multiuse(
; CHECK-NEXT: [[SH:%.*]] = lshr exact i32 %x, 7
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[SH]], 1024
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 %x, 131072
; CHECK-NEXT: call void @foo(i32 [[SH]])
; CHECK-NEXT: ret i1 [[CMP]]
;
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