[llvm] 5eedfff - [ValueTracking] Add additional cases for `isKnownNonZero(mul X, Y)`
Noah Goldstein via llvm-commits
llvm-commits at lists.llvm.org
Sun Apr 30 08:07:24 PDT 2023
Author: Noah Goldstein
Date: 2023-04-30T10:06:46-05:00
New Revision: 5eedfff695868087452b3272a42fa1a22b5d610e
URL: https://github.com/llvm/llvm-project/commit/5eedfff695868087452b3272a42fa1a22b5d610e
DIFF: https://github.com/llvm/llvm-project/commit/5eedfff695868087452b3272a42fa1a22b5d610e.diff
LOG: [ValueTracking] Add additional cases for `isKnownNonZero(mul X, Y)`
If either `X` or `Y` is odd and the other is non-zero, the result is
non-zero.
Alive2 Link:
https://alive2.llvm.org/ce/z/9V7-es
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D149418
Added:
Modified:
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Analysis/ValueTracking/known-non-zero.ll
Removed:
################################################################################
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index fa267cef3d1f..41fabbd48d8b 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2872,11 +2872,24 @@ bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
// 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);
+
+ return KnownBits::mul(XKnown, YKnown).isNonZero();
}
case Instruction::Select:
// (C ? X : Y) != 0 if X != 0 and Y != 0.
diff --git a/llvm/test/Analysis/ValueTracking/known-non-zero.ll b/llvm/test/Analysis/ValueTracking/known-non-zero.ll
index 6e688b13a089..6b7ecdcc6f68 100644
--- a/llvm/test/Analysis/ValueTracking/known-non-zero.ll
+++ b/llvm/test/Analysis/ValueTracking/known-non-zero.ll
@@ -767,13 +767,9 @@ define i1 @cttz_nonzero_fail_maybe_odd(i8 %xx, i8 %cnt, i8 %ind) {
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
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