Correctly combine alias.scope metadata by a union instead of intersecting

Summary:
The alias.scope metadata represents sets of things an instruction might
alias with. When generically combining the metadata from two
instructions the result must be the union of the original sets, because
the new instruction might alias with anything any of the original
instructions aliased with.

Reviewers: hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D7490

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228525 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/IR/Metadata.h b/include/llvm/IR/Metadata.h
index 66baa962880ee340a47f27da3e503d77956fba90..da6d5cb5e7ccf0130b8f3ce172bc362ce041fc99 100644 (file)
--- a/include/llvm/IR/Metadata.h
+++ b/include/llvm/IR/Metadata.h
@@ -879,6 +879,7 @@ public:
   static MDNode *getMostGenericTBAA(MDNode *A, MDNode *B);
   static MDNode *getMostGenericFPMath(MDNode *A, MDNode *B);
   static MDNode *getMostGenericRange(MDNode *A, MDNode *B);
+  static MDNode *getMostGenericAliasScope(MDNode *A, MDNode *B);
 };
 
 /// \brief Tuple of metadata.

diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 085ce920139b44048a3ed2ecbfe1c8f8dd1798c2..ff8955870cb554e9fc477d82d1032053c874f083 100644 (file)
--- a/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -623,8 +623,8 @@ void Instruction::getAAMetadata(AAMDNodes &N, bool Merge) const {
     N.TBAA = getMetadata(LLVMContext::MD_tbaa);
 
   if (Merge)
-    N.Scope =
-        MDNode::intersect(N.Scope, getMetadata(LLVMContext::MD_alias_scope));
+    N.Scope = MDNode::getMostGenericAliasScope(
+        N.Scope, getMetadata(LLVMContext::MD_alias_scope));
   else
     N.Scope = getMetadata(LLVMContext::MD_alias_scope);
 

diff --git a/lib/IR/Metadata.cpp b/lib/IR/Metadata.cpp
index 6227c209352c78e477376aa2c6eb6194599482ee..55dc96b10bfa14828443bf4b239b277400ab7433 100644 (file)
--- a/lib/IR/Metadata.cpp
+++ b/lib/IR/Metadata.cpp
@@ -782,6 +782,28 @@ MDNode *MDNode::intersect(MDNode *A, MDNode *B) {
   return getOrSelfReference(A->getContext(), MDs);
 }
 
+MDNode *MDNode::getMostGenericAliasScope(MDNode *A, MDNode *B) {
+  if (!A || !B)
+    return nullptr;
+
+  SmallVector<Metadata *, 4> MDs(B->op_begin(), B->op_end());
+  for (unsigned i = 0, ie = A->getNumOperands(); i != ie; ++i) {
+    Metadata *MD = A->getOperand(i);
+    bool insert = true;
+    for (unsigned j = 0, je = B->getNumOperands(); j != je; ++j)
+      if (MD == B->getOperand(j)) {
+        insert = false;
+        break;
+      }
+    if (insert)
+        MDs.push_back(MD);
+  }
+
+  // FIXME: This preserves long-standing behaviour, but is it really the right
+  // behaviour?  Or was that an unintended side-effect of node uniquing?
+  return getOrSelfReference(A->getContext(), MDs);
+}
+
 MDNode *MDNode::getMostGenericFPMath(MDNode *A, MDNode *B) {
   if (!A || !B)
     return nullptr;

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 648d605a618d398bcbe406d7c8f38748487bf7f0..c2dfaf52746d5d4aed511111d2882c9bbde25d7c 100644 (file)
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -1334,6 +1334,8 @@ void llvm::combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsign
         K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
         break;
       case LLVMContext::MD_alias_scope:
+        K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
+        break;
       case LLVMContext::MD_noalias:
         K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
         break;

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index d1a843828c33f794dd747959504bdcdb31bf1bd8..38763beb744d8b68a987cc9defa36afd8afb366f 100644 (file)
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -217,6 +217,8 @@ static Instruction *propagateMetadata(Instruction *I, ArrayRef<Value *> VL) {
         MD = MDNode::getMostGenericTBAA(MD, IMD);
         break;
       case LLVMContext::MD_alias_scope:
+        MD = MDNode::getMostGenericAliasScope(MD, IMD);
+        break;
       case LLVMContext::MD_noalias:
         MD = MDNode::intersect(MD, IMD);
         break;

diff --git a/test/Transforms/Util/combine-alias-scope-metadata.ll b/test/Transforms/Util/combine-alias-scope-metadata.ll
new file mode 100644 (file)
index 0000000..fd0a3d5
--- /dev/null
+++ b/test/Transforms/Util/combine-alias-scope-metadata.ll
@@ -0,0 +1,24 @@
+; RUN: opt < %s -S -basicaa -memcpyopt | FileCheck %s
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @test(i8* noalias dereferenceable(1) %in, i8* noalias dereferenceable(1) %out) {
+  %tmp = alloca i8
+  %tmp2 = alloca i8
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %out, i8* %in, i64 1, i32 8, i1 false)
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp, i8* %in, i64 1, i32 8, i1 false), !alias.scope !4
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp2, i8* %tmp, i64 1, i32 8, i1 false), !alias.scope !5
+
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %out, i8* %tmp2, i64 1, i32 8, i1 false), !noalias !6
+
+  ret void
+}
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8*, i8*, i64, i32, i1)
+
+!0 = !{!0}
+!1 = distinct !{!1, !0, !"in"}
+!2 = distinct !{!2, !0, !"tmp"}
+!3 = distinct !{!3, !0, !"tmp2"}
+!4 = distinct !{!1, !2}
+!5 = distinct !{!2, !3}
+!6 = distinct !{!1, !2}