[PATCH] D67562: [MemorySSA] Update MSSA for non-conventional AA.

[Alina Sbirlea via Phabricator via llvm-commits]

asbirlea updated this revision to Diff 220381.
asbirlea marked 3 inline comments as done.
asbirlea added a comment.

Address comments.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67562/new/

https://reviews.llvm.org/D67562

Files:
  lib/Analysis/MemorySSA.cpp
  test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll


Index: test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll
===================================================================
--- /dev/null
+++ test/Analysis/MemorySSA/loop-rotate-disablebasicaa.ll
@@ -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
+
+
Index: lib/Analysis/MemorySSA.cpp
===================================================================
--- lib/Analysis/MemorySSA.cpp
+++ lib/Analysis/MemorySSA.cpp
@@ -1739,6 +1739,12 @@
     if (II->getIntrinsicID() == Intrinsic::assume || isa<DbgInfoIntrinsic>(II))
       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;


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