From ab4684e26fe21857d8c8bc6ba7a5234c35117c83 Mon Sep 17 00:00:00 2001
From: Hal Finkel <hfinkel@anl.gov>
Date: Sat, 16 Jun 2012 20:34:06 +0000
Subject: Teach BBVectorize to combine, when possible, or discard metadata when
 fusing instructions.

The present implementation handles only TBAA and FP metadata, discarding everything else.
For debug metadata, the current behavior is maintained (the debug metadata associated with
one of the instructions will be kept, discarding that attached to the other).

This should address PR 13040.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158606 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Vectorize/BBVectorize.cpp | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

(limited to 'lib')

diff --git a/lib/Transforms/Vectorize/BBVectorize.cpp b/lib/Transforms/Vectorize/BBVectorize.cpp
index 1d08df5..8c442bf 100644
--- a/lib/Transforms/Vectorize/BBVectorize.cpp
+++ b/lib/Transforms/Vectorize/BBVectorize.cpp
@@ -23,6 +23,7 @@
 #include "llvm/IntrinsicInst.h"
 #include "llvm/Intrinsics.h"
 #include "llvm/LLVMContext.h"
+#include "llvm/Metadata.h"
 #include "llvm/Pass.h"
 #include "llvm/Type.h"
 #include "llvm/ADT/DenseMap.h"
@@ -303,6 +304,8 @@ namespace {
                      Instruction *&InsertionPt,
                      Instruction *I, Instruction *J);
 
+    void combineMetadata(Instruction *K, const Instruction *J);
+
     bool vectorizeBB(BasicBlock &BB) {
       bool changed = false;
       // Iterate a sufficient number of times to merge types of size 1 bit,
@@ -1784,6 +1787,31 @@ namespace {
     }
   }
 
+  // When the first instruction in each pair is cloned, it will inherit its
+  // parent's metadata. This metadata must be combined with that of the other
+  // instruction in a safe way.
+  void BBVectorize::combineMetadata(Instruction *K, const Instruction *J) {
+    SmallVector<std::pair<unsigned, MDNode*>, 4> Metadata;
+    K->getAllMetadataOtherThanDebugLoc(Metadata);
+    for (unsigned i = 0, n = Metadata.size(); i < n; ++i) {
+      unsigned Kind = Metadata[i].first;
+      MDNode *JMD = J->getMetadata(Kind);
+      MDNode *KMD = Metadata[i].second;
+
+      switch (Kind) {
+      default:
+        K->setMetadata(Kind, 0); // Remove unknown metadata
+        break;
+      case LLVMContext::MD_tbaa:
+        K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
+        break;
+      case LLVMContext::MD_fpmath:
+        K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
+        break;
+      }
+    }
+  }
+
   // This function fuses the chosen instruction pairs into vector instructions,
   // taking care preserve any needed scalar outputs and, then, it reorders the
   // remaining instructions as needed (users of the first member of the pair
@@ -1863,6 +1891,8 @@ namespace {
       if (!isa<StoreInst>(K))
         K->mutateType(getVecTypeForPair(I->getType()));
 
+      combineMetadata(K, J);
+
       for (unsigned o = 0; o < NumOperands; ++o)
         K->setOperand(o, ReplacedOperands[o]);
 
-- 
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