[llvm] 59eae91 - [ValueTracking] Don't use CondContext in dataflow analysis of phi nodes (#100316)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 24 05:06:40 PDT 2024
Author: Yingwei Zheng
Date: 2024-07-24T20:06:36+08:00
New Revision: 59eae919c938f890e9b9b4be8a3fa3cb1b11ed89
URL: https://github.com/llvm/llvm-project/commit/59eae919c938f890e9b9b4be8a3fa3cb1b11ed89
DIFF: https://github.com/llvm/llvm-project/commit/59eae919c938f890e9b9b4be8a3fa3cb1b11ed89.diff
LOG: [ValueTracking] Don't use CondContext in dataflow analysis of phi nodes (#100316)
See the following case:
```
define i16 @pr100298() {
entry:
br label %for.inc
for.inc:
%indvar = phi i32 [ -15, %entry ], [ %mask, %for.inc ]
%add = add nsw i32 %indvar, 9
%mask = and i32 %add, 65535
%cmp1 = icmp ugt i32 %mask, 5
br i1 %cmp1, label %for.inc, label %for.end
for.end:
%conv = trunc i32 %add to i16
%cmp2 = icmp ugt i32 %mask, 3
%shl = shl nuw i16 %conv, 14
%res = select i1 %cmp2, i16 %conv, i16 %shl
ret i16 %res
}
```
When computing knownbits of `%shl` with `%cmp2=false`, we cannot use
this condition in the analysis of `%mask (%for.inc -> %for.inc)`.
Fixes https://github.com/llvm/llvm-project/issues/100298.
Added:
llvm/test/Transforms/InstCombine/pr100298.ll
Modified:
llvm/include/llvm/Analysis/SimplifyQuery.h
llvm/lib/Analysis/ValueTracking.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/SimplifyQuery.h b/llvm/include/llvm/Analysis/SimplifyQuery.h
index a560744f01222..e8f43c8c2e91f 100644
--- a/llvm/include/llvm/Analysis/SimplifyQuery.h
+++ b/llvm/include/llvm/Analysis/SimplifyQuery.h
@@ -130,6 +130,12 @@ struct SimplifyQuery {
Copy.CC = &CC;
return Copy;
}
+
+ SimplifyQuery getWithoutCondContext() const {
+ SimplifyQuery Copy(*this);
+ Copy.CC = nullptr;
+ return Copy;
+ }
};
} // end namespace llvm
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 40fe1ffe13f1b..4b77c0046cc70 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1435,7 +1435,7 @@ static void computeKnownBitsFromOperator(const Operator *I,
// inferred hold at original context instruction. TODO: It may be
// correct to use the original context. IF warranted, explore and
// add sufficient tests to cover.
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
RecQ.CxtI = P;
computeKnownBits(R, DemandedElts, Known2, Depth + 1, RecQ);
switch (Opcode) {
@@ -1468,7 +1468,7 @@ static void computeKnownBitsFromOperator(const Operator *I,
// phi. This is important because that is where the value is actually
// "evaluated" even though it is used later somewhere else. (see also
// D69571).
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
unsigned OpNum = P->getOperand(0) == R ? 0 : 1;
Instruction *RInst = P->getIncomingBlock(OpNum)->getTerminator();
@@ -1546,7 +1546,7 @@ static void computeKnownBitsFromOperator(const Operator *I,
// phi. This is important because that is where the value is actually
// "evaluated" even though it is used later somewhere else. (see also
// D69571).
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
RecQ.CxtI = P->getIncomingBlock(u)->getTerminator();
Known2 = KnownBits(BitWidth);
@@ -2329,7 +2329,7 @@ bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
// it is an induction variable where in each step its value is a power of
// two.
auto *PN = cast<PHINode>(I);
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
// Check if it is an induction variable and always power of two.
if (isPowerOfTwoRecurrence(PN, OrZero, Depth, RecQ))
@@ -2943,7 +2943,7 @@ static bool isKnownNonZeroFromOperator(const Operator *I,
return true;
// Check if all incoming values are non-zero using recursion.
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
return llvm::all_of(PN->operands(), [&](const Use &U) {
if (U.get() == PN)
@@ -3509,7 +3509,7 @@ static bool isNonEqualPHIs(const PHINode *PN1, const PHINode *PN2,
if (UsedFullRecursion)
return false;
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
RecQ.CxtI = IncomBB->getTerminator();
if (!isKnownNonEqual(IV1, IV2, DemandedElts, Depth + 1, RecQ))
return false;
@@ -4001,7 +4001,7 @@ static unsigned ComputeNumSignBitsImpl(const Value *V,
// Take the minimum of all incoming values. This can't infinitely loop
// because of our depth threshold.
- SimplifyQuery RecQ = Q;
+ SimplifyQuery RecQ = Q.getWithoutCondContext();
Tmp = TyBits;
for (unsigned i = 0, e = NumIncomingValues; i != e; ++i) {
if (Tmp == 1) return Tmp;
@@ -5909,10 +5909,10 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
// Recurse, but cap the recursion to two levels, because we don't want
// to waste time spinning around in loops. We need at least depth 2 to
// detect known sign bits.
- computeKnownFPClass(
- IncValue, DemandedElts, InterestedClasses, KnownSrc,
- PhiRecursionLimit,
- Q.getWithInstruction(P->getIncomingBlock(U)->getTerminator()));
+ computeKnownFPClass(IncValue, DemandedElts, InterestedClasses, KnownSrc,
+ PhiRecursionLimit,
+ Q.getWithoutCondContext().getWithInstruction(
+ P->getIncomingBlock(U)->getTerminator()));
if (First) {
Known = KnownSrc;
diff --git a/llvm/test/Transforms/InstCombine/pr100298.ll b/llvm/test/Transforms/InstCombine/pr100298.ll
new file mode 100644
index 0000000000000..6cf2a71bb916e
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr100298.ll
@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+; Make sure that the result of computeKnownBits for %indvar is correct.
+
+define i16 @pr100298() {
+; CHECK-LABEL: define i16 @pr100298() {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: br label %[[FOR_INC:.*]]
+; CHECK: [[FOR_INC]]:
+; CHECK-NEXT: [[INDVAR:%.*]] = phi i32 [ -15, %[[ENTRY]] ], [ [[MASK:%.*]], %[[FOR_INC]] ]
+; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[INDVAR]], 9
+; CHECK-NEXT: [[MASK]] = and i32 [[ADD]], 65535
+; CHECK-NEXT: [[CMP1:%.*]] = icmp ugt i32 [[MASK]], 5
+; CHECK-NEXT: br i1 [[CMP1]], label %[[FOR_INC]], label %[[FOR_END:.*]]
+; CHECK: [[FOR_END]]:
+; CHECK-NEXT: [[CONV:%.*]] = trunc i32 [[ADD]] to i16
+; CHECK-NEXT: [[CMP2:%.*]] = icmp ugt i32 [[MASK]], 3
+; CHECK-NEXT: [[SHL:%.*]] = shl nuw i16 [[CONV]], 14
+; CHECK-NEXT: [[RES:%.*]] = select i1 [[CMP2]], i16 [[CONV]], i16 [[SHL]]
+; CHECK-NEXT: ret i16 [[RES]]
+;
+entry:
+ br label %for.inc
+
+for.inc:
+ %indvar = phi i32 [ -15, %entry ], [ %mask, %for.inc ]
+ %add = add nsw i32 %indvar, 9
+ %mask = and i32 %add, 65535
+ %cmp1 = icmp ugt i32 %mask, 5
+ br i1 %cmp1, label %for.inc, label %for.end
+
+for.end:
+ %conv = trunc i32 %add to i16
+ %cmp2 = icmp ugt i32 %mask, 3
+ %shl = shl nuw i16 %conv, 14
+ %res = select i1 %cmp2, i16 %conv, i16 %shl
+ ret i16 %res
+}
More information about the llvm-commits
mailing list