[llvm] dff3d8a - [ValueTracking] Add support for `mul` in `isKnownToBeAPowerOfTwo`
Noah Goldstein via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 9 12:45:47 PDT 2023
Author: Noah Goldstein
Date: 2023-08-09T14:42:55-05:00
New Revision: dff3d8a279c660694b50271523edbc98c3eb2ab6
URL: https://github.com/llvm/llvm-project/commit/dff3d8a279c660694b50271523edbc98c3eb2ab6
DIFF: https://github.com/llvm/llvm-project/commit/dff3d8a279c660694b50271523edbc98c3eb2ab6.diff
LOG: [ValueTracking] Add support for `mul` in `isKnownToBeAPowerOfTwo`
pow2 * pow2 is a power of 2 or zero.
Proof: https://alive2.llvm.org/ce/z/FNiiXd
Differential Revision: https://reviews.llvm.org/D157308
Added:
Modified:
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Analysis/ValueTracking/known-power-of-two.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index f40894619e7697..d82c83c9a33269 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2050,6 +2050,10 @@ bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
if (Q.IIQ.isExact(cast<BinaryOperator>(I)))
return isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
return false;
+ case Instruction::Mul:
+ return OrZero &&
+ isKnownToBeAPowerOfTwo(I->getOperand(1), OrZero, Depth, Q) &&
+ isKnownToBeAPowerOfTwo(I->getOperand(0), OrZero, Depth, Q);
case Instruction::And:
if (OrZero) {
// A power of two and'd with anything is a power of two or zero.
diff --git a/llvm/test/Analysis/ValueTracking/known-power-of-two.ll b/llvm/test/Analysis/ValueTracking/known-power-of-two.ll
index 8966dad5875182..002147b390ce2c 100644
--- a/llvm/test/Analysis/ValueTracking/known-power-of-two.ll
+++ b/llvm/test/Analysis/ValueTracking/known-power-of-two.ll
@@ -379,7 +379,8 @@ define i16 @mul_is_pow2_or_zero(i16 %x, i16 %y, i16 %z) {
; CHECK-NEXT: [[XP2:%.*]] = shl i16 4, [[X]]
; CHECK-NEXT: [[ZP2:%.*]] = shl i16 2, [[Z]]
; CHECK-NEXT: [[XX:%.*]] = mul i16 [[XP2]], [[ZP2]]
-; CHECK-NEXT: [[R:%.*]] = urem i16 [[Y]], [[XX]]
+; CHECK-NEXT: [[TMP1:%.*]] = add i16 [[XX]], -1
+; CHECK-NEXT: [[R:%.*]] = and i16 [[TMP1]], [[Y]]
; CHECK-NEXT: ret i16 [[R]]
;
%xp2 = shl i16 4, %x
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