[InstCombine] Merge debug locations when folding through a phi node

If all the operands to a phi node are of the same operation, instcombine
will try to pull them through the phi node, combining them into a single
operation.  When it does this, the debug location of the operation should
be the merged debug locations of the phi node arguments.

Patch 2 of 8 for D26256.  Folding of a binary operation.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289679

2 files changed, 21 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index e6b9bca1289..d13b94cb6c9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -553,6 +553,10 @@ private:
   Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
   Instruction *FoldPHIArgZextsIntoPHI(PHINode &PN);
 
+  /// Helper function for FoldPHIArgXIntoPHI() to get debug location for the
+  /// folded operation.
+  DebugLoc PHIArgMergedDebugLoc(PHINode &PN);
+
   Instruction *foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
                            ICmpInst::Predicate Cond, Instruction &I);
   Instruction *foldAllocaCmp(ICmpInst &ICI, const AllocaInst *Alloca,
diff --git a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
index 675a5d17ad9..91bfe6c5c82 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -18,11 +18,27 @@
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/IR/DebugInfo.h"
 using namespace llvm;
 using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "instcombine"
 
+/// The PHI arguments will be folded into a single operation with a PHI node
+/// as input. The debug location of the single operation will be the merged
+/// locations of the original PHI node arguments.
+DebugLoc InstCombiner::PHIArgMergedDebugLoc(PHINode &PN) {
+  auto *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
+  DILocation *Loc = FirstInst->getDebugLoc();
+
+  for (unsigned i = 1; i != PN.getNumIncomingValues(); ++i) {
+    auto *I = cast<Instruction>(PN.getIncomingValue(i));
+    Loc = DILocation::getMergedLocation(Loc, I->getDebugLoc());
+  }
+
+  return Loc;
+}
+
 /// If we have something like phi [add (a,b), add(a,c)] and if a/b/c and the
 /// adds all have a single use, turn this into a phi and a single binop.
 Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
@@ -114,7 +130,7 @@ Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
   for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i)
     NewBinOp->andIRFlags(PN.getIncomingValue(i));
 
-  NewBinOp->setDebugLoc(FirstInst->getDebugLoc());
+  NewBinOp->setDebugLoc(PHIArgMergedDebugLoc(PN));
   return NewBinOp;
 }