[llvm] bff1f8c - [InstCombine] complete (X << Z) / (Y << Z) --> X / Y
Ben Shi via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 22 19:57:13 PST 2022
Author: Chenbing Zheng
Date: 2022-12-23T11:56:52+08:00
New Revision: bff1f8c79beeb8f83b37be1fb23fa44330799250
URL: https://github.com/llvm/llvm-project/commit/bff1f8c79beeb8f83b37be1fb23fa44330799250
DIFF: https://github.com/llvm/llvm-project/commit/bff1f8c79beeb8f83b37be1fb23fa44330799250.diff
LOG: [InstCombine] complete (X << Z) / (Y << Z) --> X / Y
Add one more situations for this fold.
For unsigned div, 'nsw' on both shifts + 'nuw' on the dividend.
Alive2: https://alive2.llvm.org/ce/z/sELF76
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D139997
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
llvm/test/Transforms/InstCombine/div-shift.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 96275302e86d9..6eb7a66226865 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -888,9 +888,13 @@ static Instruction *foldIDivShl(BinaryOperator &I,
auto *Shl0 = cast<OverflowingBinaryOperator>(Op0);
auto *Shl1 = cast<OverflowingBinaryOperator>(Op1);
- // For unsigned div, we need 'nuw' on both shifts.
+ // For unsigned div, we need 'nuw' on both shifts or
+ // 'nsw' on both shifts + 'nuw' on the dividend.
// (X << Z) / (Y << Z) --> X / Y
- if (!IsSigned && Shl0->hasNoUnsignedWrap() && Shl1->hasNoUnsignedWrap())
+ if (!IsSigned &&
+ ((Shl0->hasNoUnsignedWrap() && Shl1->hasNoUnsignedWrap()) ||
+ (Shl0->hasNoUnsignedWrap() && Shl0->hasNoSignedWrap() &&
+ Shl1->hasNoSignedWrap())))
Ret = BinaryOperator::CreateUDiv(X, Y);
// For signed div, we need 'nsw' on both shifts + 'nuw' on the divisor.
diff --git a/llvm/test/Transforms/InstCombine/div-shift.ll b/llvm/test/Transforms/InstCombine/div-shift.ll
index b35d8bd3175cd..4e8f0fcaa22cb 100644
--- a/llvm/test/Transforms/InstCombine/div-shift.ll
+++ b/llvm/test/Transforms/InstCombine/div-shift.ll
@@ -951,13 +951,9 @@ define i8 @udiv_shl_shl_nsw_nuw(i8 %x, i8 %y, i8 %z) {
ret i8 %d
}
-; TODO: This could fold.
-
define i8 @udiv_shl_shl_nuw_nsw2(i8 %x, i8 %y, i8 %z) {
; CHECK-LABEL: @udiv_shl_shl_nuw_nsw2(
-; CHECK-NEXT: [[XZ:%.*]] = shl nuw nsw i8 [[X:%.*]], [[Z:%.*]]
-; CHECK-NEXT: [[YZ:%.*]] = shl nsw i8 [[Y:%.*]], [[Z]]
-; CHECK-NEXT: [[D:%.*]] = udiv i8 [[XZ]], [[YZ]]
+; CHECK-NEXT: [[D:%.*]] = udiv i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i8 [[D]]
;
%xz = shl nuw nsw i8 %x, %z
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