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
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);
}
--- /dev/null
+; 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
+}