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NewGVN: Fix PR 31573, a failure to verify memory congruency due to

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not excluding ourselves when checking if any equivalent stores
exist.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291421 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Berlin 2017-01-09 05:34:29 +00:00
parent 66e9c6aac6
commit b393b33bb9
2 changed files with 56 additions and 1 deletions
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15
lib/Transforms/Scalar/NewGVN.cpp
View File

@ -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);
}

42
test/Transforms/NewGVN/pr31573.ll Normal file
View File

@ -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
}