[llvm] r372137 - [MemorySSA] Update MSSA for non-conventional AA.
Alina Sbirlea via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 17 09:31:37 PDT 2019
Author: asbirlea
Date: Tue Sep 17 09:31:37 2019
New Revision: 372137
URL: http://llvm.org/viewvc/llvm-project?rev=372137&view=rev
Log:
[MemorySSA] Update MSSA for non-conventional AA.
Summary:
Regularly when moving an instruction that may not read or write memory,
the instruction is not modelled in MSSA, so not action is necessary.
For a non-conventional AA pipeline, MSSA needs to explicitly check when
creating accesses, so as to not model instructions that may not read and
write memory.
Reviewers: george.burgess.iv
Subscribers: Prazek, sanjoy.google, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67562
Added:
llvm/trunk/test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll
Modified:
llvm/trunk/lib/Analysis/MemorySSA.cpp
Modified: llvm/trunk/lib/Analysis/MemorySSA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemorySSA.cpp?rev=372137&r1=372136&r2=372137&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/MemorySSA.cpp (original)
+++ llvm/trunk/lib/Analysis/MemorySSA.cpp Tue Sep 17 09:31:37 2019
@@ -1736,9 +1736,15 @@ MemoryUseOrDef *MemorySSA::createNewAcce
// FIXME: Replace this special casing with a more accurate modelling of
// assume's control dependency.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
- if (II->getIntrinsicID() == Intrinsic::assume || isa<DbgInfoIntrinsic>(II))
+ if (II->getIntrinsicID() == Intrinsic::assume)
return nullptr;
+ // Using a nonstandard AA pipelines might leave us with unexpected modref
+ // results for I, so add a check to not model instructions that may not read
+ // from or write to memory. This is necessary for correctness.
+ if (!I->mayReadFromMemory() && !I->mayWriteToMemory())
+ return nullptr;
+
bool Def, Use;
if (Template) {
Def = dyn_cast_or_null<MemoryDef>(Template) != nullptr;
Added: llvm/trunk/test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll?rev=372137&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll (added)
+++ llvm/trunk/test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll Tue Sep 17 09:31:37 2019
@@ -0,0 +1,26 @@
+; RUN: opt -disable-basicaa -print-memoryssa -disable-output %s 2>&1 | FileCheck %s
+
+; Note: if @foo is modelled as a MemoryDef, this test will assert with -loop-rotate, due to MemorySSA not
+; being preserved when moving instructions that may not read from or write to memory.
+
+; CHECK-LABEL: @main
+; CHECK-NOT: MemoryDef
+define void @main() {
+entry:
+ br label %for.cond120
+
+for.cond120: ; preds = %for.body127, %entry
+ call void @foo()
+ br i1 undef, label %for.body127, label %for.cond.cleanup126
+
+for.cond.cleanup126: ; preds = %for.cond120
+ unreachable
+
+for.body127: ; preds = %for.cond120
+ %0 = load i16**, i16*** undef, align 1
+ br label %for.cond120
+}
+
+declare void @foo() readnone
+
+
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