Don't passively concatenate MDNodes

I have audited all the callers of concatenate and none require duplicate
entries to service concatenation.
These duplicates serve no purpose but to needlessly embiggen the IR.

N.B. Layering getMostGenericAliasScope on top of concatenate makes it
O(nlogn + mlogm) instead of O(n*m).

llvm-svn: 278836

2 files changed, 7 insertions, 15 deletions

diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index 5e41b9f410e..9168aa0ddf1 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -16,6 +16,7 @@
 #include "MetadataImpl.h"
 #include "SymbolTableListTraitsImpl.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/IR/ConstantRange.h"
@@ -862,14 +863,12 @@ MDNode *MDNode::concatenate(MDNode *A, MDNode *B) {
   if (!B)
     return A;
 
-  SmallVector<Metadata *, 4> MDs;
-  MDs.reserve(A->getNumOperands() + B->getNumOperands());
-  MDs.append(A->op_begin(), A->op_end());
-  MDs.append(B->op_begin(), B->op_end());
+  SmallSetVector<Metadata *, 4> MDs(A->op_begin(), A->op_end());
+  MDs.insert(B->op_begin(), B->op_end());
 
   // 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);
+  return getOrSelfReference(A->getContext(), MDs.getArrayRef());
 }
 
 MDNode *MDNode::intersect(MDNode *A, MDNode *B) {
@@ -890,14 +889,7 @@ MDNode *MDNode::getMostGenericAliasScope(MDNode *A, MDNode *B) {
   if (!A || !B)
     return nullptr;
 
-  SmallVector<Metadata *, 4> MDs(B->op_begin(), B->op_end());
-  for (Metadata *MD : A->operands())
-    if (!is_contained(B->operands(), MD))
-      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);
+  return concatenate(A, B);
 }
 
 MDNode *MDNode::getMostGenericFPMath(MDNode *A, MDNode *B) {
diff --git a/llvm/test/Transforms/InstCombine/fold-phi-load-metadata.ll b/llvm/test/Transforms/InstCombine/fold-phi-load-metadata.ll
index 7fa26b46e25..e5a1aa7362a 100644
--- a/llvm/test/Transforms/InstCombine/fold-phi-load-metadata.ll
+++ b/llvm/test/Transforms/InstCombine/fold-phi-load-metadata.ll
@@ -40,10 +40,10 @@ return:                                           ; preds = %if.end, %if.then
 ; CHECK: ![[TBAA]] = !{![[TAG1:[0-9]+]], ![[TAG1]], i64 0}
 ; CHECK: ![[TAG1]] = !{!"int", !{{[0-9]+}}, i64 0}
 ; CHECK: ![[RANGE]] = !{i32 10, i32 25}
-; CHECK: ![[ALIAS_SCOPE]] = !{![[SCOPE0:[0-9]+]], ![[SCOPE1:[0-9]+]], ![[SCOPE2:[0-9]+]]}
+; CHECK: ![[ALIAS_SCOPE]] = !{![[SCOPE0:[0-9]+]], ![[SCOPE2:[0-9]+]], ![[SCOPE1:[0-9]+]]}
 ; CHECK: ![[SCOPE0]] = distinct !{![[SCOPE0]], !{{[0-9]+}}, !"scope0"}
-; CHECK: ![[SCOPE1]] = distinct !{![[SCOPE1]], !{{[0-9]+}}, !"scope1"}
 ; CHECK: ![[SCOPE2]] = distinct !{![[SCOPE2]], !{{[0-9]+}}, !"scope2"}
+; CHECK: ![[SCOPE1]] = distinct !{![[SCOPE1]], !{{[0-9]+}}, !"scope1"}
 ; CHECK: ![[NOALIAS]] = !{![[SCOPE3:[0-9]+]]}
 ; CHECK: ![[SCOPE3]] = distinct !{![[SCOPE3]], !{{[0-9]+}}, !"scope3"}