[PATCH] D139997: [InstCombine] complete (X << Z) / (Y << Z) --> X / Y
Ben Shi via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 22 19:57:26 PST 2022
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGbff1f8c79bee: [InstCombine] complete (X << Z) / (Y << Z) --> X / Y (authored by Chenbing.Zheng, committed by benshi001).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D139997/new/
https://reviews.llvm.org/D139997
Files:
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
llvm/test/Transforms/InstCombine/div-shift.ll
Index: llvm/test/Transforms/InstCombine/div-shift.ll
===================================================================
--- llvm/test/Transforms/InstCombine/div-shift.ll
+++ llvm/test/Transforms/InstCombine/div-shift.ll
@@ -951,13 +951,9 @@
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
Index: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -888,9 +888,13 @@
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.
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