[PATCH] D149418: [ValueTracking] Add additional cases for `isKnownNonZero(mul X, Y)`
Noah Goldstein via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sat Apr 29 15:10:27 PDT 2023
goldstein.w.n updated this revision to Diff 518251.
goldstein.w.n marked an inline comment as done.
goldstein.w.n added a comment.
use `KnownBits::mul` instead of refactoring and using `computeKnownBitsMul`
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D149418/new/
https://reviews.llvm.org/D149418
Files:
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Analysis/ValueTracking/known-non-zero.ll
Index: llvm/test/Analysis/ValueTracking/known-non-zero.ll
===================================================================
--- llvm/test/Analysis/ValueTracking/known-non-zero.ll
+++ llvm/test/Analysis/ValueTracking/known-non-zero.ll
@@ -767,13 +767,9 @@
define i1 @mul_nonzero_odd(i8 %xx, i8 %y, i8 %ind) {
; CHECK-LABEL: @mul_nonzero_odd(
-; CHECK-NEXT: [[XO:%.*]] = or i8 [[XX:%.*]], 1
; CHECK-NEXT: [[Y_NZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[Y_NZ]])
-; CHECK-NEXT: [[X:%.*]] = mul i8 [[XO]], [[Y]]
-; CHECK-NEXT: [[Z:%.*]] = or i8 [[X]], [[IND:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp eq i8 [[Z]], 0
-; CHECK-NEXT: ret i1 [[R]]
+; CHECK-NEXT: ret i1 false
;
%xo = or i8 %xx, 1
%y_nz = icmp ne i8 %y, 0
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -2872,11 +2872,30 @@
// If X and Y are non-zero then so is X * Y as long as the multiplication
// does not overflow.
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
- if ((Q.IIQ.hasNoSignedWrap(BO) || Q.IIQ.hasNoUnsignedWrap(BO)) &&
- isKnownNonZero(I->getOperand(0), DemandedElts, Depth, Q) &&
- isKnownNonZero(I->getOperand(1), DemandedElts, Depth, Q))
- return true;
- break;
+ if (Q.IIQ.hasNoSignedWrap(BO) || Q.IIQ.hasNoUnsignedWrap(BO))
+ return isKnownNonZero(I->getOperand(0), DemandedElts, Depth, Q) &&
+ isKnownNonZero(I->getOperand(1), DemandedElts, Depth, Q);
+
+ // If either X or Y is odd, then if the other is non-zero the result can't
+ // be zero.
+ KnownBits XKnown =
+ computeKnownBits(I->getOperand(0), DemandedElts, Depth, Q);
+ if (XKnown.One[0])
+ return isKnownNonZero(I->getOperand(1), DemandedElts, Depth, Q);
+
+ KnownBits YKnown =
+ computeKnownBits(I->getOperand(1), DemandedElts, Depth, Q);
+ if (YKnown.One[0])
+ return XKnown.isNonZero() ||
+ isKnownNonZero(I->getOperand(0), DemandedElts, Depth, Q);
+
+ // This is a copy of the tail code for `computeKnownBitsMul`. We don't need
+ // the full logic as we know `NSW` is not set.
+ bool SelfMultiply = I->getOperand(0) == I->getOperand(1);
+ if (SelfMultiply)
+ SelfMultiply &= isGuaranteedNotToBeUndefOrPoison(I->getOperand(0), Q.AC,
+ Q.CxtI, Q.DT, Depth + 1);
+ return KnownBits::mul(XKnown, YKnown, SelfMultiply).isNonZero();
}
case Instruction::Select:
// (C ? X : Y) != 0 if X != 0 and Y != 0.
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