diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/NewGVN.cpp | 15 | ||||
| -rw-r--r-- | llvm/test/Transforms/NewGVN/pr31573.ll | 42 |
2 files changed, 56 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp index 1059fcd829b..eef7db08cd4 100644 --- a/llvm/lib/Transforms/Scalar/NewGVN.cpp +++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp @@ -714,6 +714,15 @@ const StoreExpression *NewGVN::createStoreExpression(StoreInst *SI, return E; } +// Utility function to check whether the congruence class has a member other +// than the given instruction. +bool hasMemberOtherThanUs(const CongruenceClass *CC, Instruction *I) { + // Either it has more than one member, in which case it must contain something + // other than us (because it's indexed by value), or if it only has one member + // right now, that member should not be us. + return CC->Members.size() > 1 || CC->Members.count(I) == 0; +} + const Expression *NewGVN::performSymbolicStoreEvaluation(Instruction *I, const BasicBlock *B) { // Unlike loads, we never try to eliminate stores, so we do not check if they @@ -729,8 +738,12 @@ const Expression *NewGVN::performSymbolicStoreEvaluation(Instruction *I, cast<MemoryDef>(StoreAccess)->getDefiningAccess()); const Expression *OldStore = createStoreExpression(SI, StoreRHS, B); CongruenceClass *CC = ExpressionToClass.lookup(OldStore); + // Basically, check if the congruence class the store is in is defined by a + // store that isn't us, and has the same value. MemorySSA takes care of + // ensuring the store has the same memory state as us already. if (CC && CC->DefiningExpr && isa<StoreExpression>(CC->DefiningExpr) && - CC->RepLeader == lookupOperandLeader(SI->getValueOperand(), SI, B)) + CC->RepLeader == lookupOperandLeader(SI->getValueOperand(), SI, B) && + hasMemberOtherThanUs(CC, I)) return createStoreExpression(SI, StoreRHS, B); } diff --git a/llvm/test/Transforms/NewGVN/pr31573.ll b/llvm/test/Transforms/NewGVN/pr31573.ll new file mode 100644 index 00000000000..0450b4b1299 --- /dev/null +++ b/llvm/test/Transforms/NewGVN/pr31573.ll @@ -0,0 +1,42 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt < %s -basicaa -newgvn -S | FileCheck %s + +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" + +define void @patatino(i8* %blah) { +; CHECK-LABEL: @patatino( +; CHECK-NEXT: entry: +; CHECK-NEXT: br label [[WHILE_COND:%.*]] +; CHECK: while.cond: +; CHECK-NEXT: [[MEH:%.*]] = phi i8* [ [[BLAH:%.*]], [[ENTRY:%.*]] ], [ null, [[WHILE_BODY:%.*]] ] +; CHECK-NEXT: switch i32 undef, label [[WHILE_BODY]] [ +; CHECK-NEXT: i32 666, label [[WHILE_END:%.*]] +; CHECK-NEXT: ] +; CHECK: while.body: +; CHECK-NEXT: br label [[WHILE_COND]] +; CHECK: while.end: +; CHECK-NEXT: store i8 0, i8* [[MEH]], align 1 +; CHECK-NEXT: store i8 0, i8* [[BLAH]], align 1 +; CHECK-NEXT: ret void +; +entry: + br label %while.cond + +while.cond: + %meh = phi i8* [ %blah, %entry ], [ null, %while.body ] + switch i32 undef, label %while.body [ + i32 666, label %while.end + ] + +while.body: + br label %while.cond + +while.end: +;; These two stores will initially be considered equivalent, but then proven not. +;; the second store would previously end up deciding it's equivalent to a previous +;; store, but it was really just finding an optimistic version of itself +;; in the congruence class. + store i8 0, i8* %meh, align 1 + store i8 0, i8* %blah, align 1 + ret void +} |
