1 files changed, 39 insertions, 12 deletions

diff --git a/gnu/llvm/lib/Transforms/Utils/LCSSA.cpp b/gnu/llvm/lib/Transforms/Utils/LCSSA.cpp
index ae0e2bb6c28..53d444b309d 100644
--- a/gnu/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/gnu/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -10,7 +10,7 @@
 // This pass transforms loops by placing phi nodes at the end of the loops for
 // all values that are live across the loop boundary.  For example, it turns
 // the left into the right code:
-// 
+//
 // for (...)                for (...)
 //   if (c)                   if (c)
 //     X1 = ...                 X1 = ...
@@ -21,8 +21,8 @@
 //                          ... = X4 + 4
 //
 // This is still valid LLVM; the extra phi nodes are purely redundant, and will
-// be trivially eliminated by InstCombine.  The major benefit of this 
-// transformation is that it makes many other loop optimizations, such as 
+// be trivially eliminated by InstCombine.  The major benefit of this
+// transformation is that it makes many other loop optimizations, such as
 // LoopUnswitching, simpler.
 //
 //===----------------------------------------------------------------------===//
@@ -36,13 +36,15 @@
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
+#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/PredIteratorCache.h"
 #include "llvm/Pass.h"
-#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/SSAUpdater.h"
 using namespace llvm;
@@ -143,7 +145,8 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
 
       PHINode *PN = PHINode::Create(I->getType(), PredCache.size(ExitBB),
                                     I->getName() + ".lcssa", &ExitBB->front());
-
+      // Get the debug location from the original instruction.
+      PN->setDebugLoc(I->getDebugLoc());
       // Add inputs from inside the loop for this PHI.
       for (BasicBlock *Pred : PredCache.get(ExitBB)) {
         PN->addIncoming(I, Pred);
@@ -199,6 +202,21 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
       SSAUpdate.RewriteUse(*UseToRewrite);
     }
 
+    SmallVector<DbgValueInst *, 4> DbgValues;
+    llvm::findDbgValues(DbgValues, I);
+
+    // Update pre-existing debug value uses that reside outside the loop.
+    auto &Ctx = I->getContext();
+    for (auto DVI : DbgValues) {
+      BasicBlock *UserBB = DVI->getParent();
+      if (InstBB == UserBB || L->contains(UserBB))
+        continue;
+      // We currently only handle debug values residing in blocks where we have
+      // inserted a PHI instruction.
+      if (Value *V = SSAUpdate.FindValueForBlock(UserBB))
+        DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
+    }
+
     // SSAUpdater might have inserted phi-nodes inside other loops. We'll need
     // to post-process them to keep LCSSA form.
     for (PHINode *InsertedPN : InsertedPHIs) {
@@ -214,18 +232,27 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
         Worklist.push_back(PostProcessPN);
 
     // Keep track of PHI nodes that we want to remove because they did not have
-    // any uses rewritten.
+    // any uses rewritten. If the new PHI is used, store it so that we can
+    // try to propagate dbg.value intrinsics to it.
+    SmallVector<PHINode *, 2> NeedDbgValues;
     for (PHINode *PN : AddedPHIs)
       if (PN->use_empty())
         PHIsToRemove.insert(PN);
-
+      else
+        NeedDbgValues.push_back(PN);
+    insertDebugValuesForPHIs(InstBB, NeedDbgValues);
     Changed = true;
   }
-  // Remove PHI nodes that did not have any uses rewritten.
-  for (PHINode *PN : PHIsToRemove) {
-    assert (PN->use_empty() && "Trying to remove a phi with uses.");
-    PN->eraseFromParent();
-  }
+  // Remove PHI nodes that did not have any uses rewritten. We need to redo the
+  // use_empty() check here, because even if the PHI node wasn't used when added
+  // to PHIsToRemove, later added PHI nodes can be using it.  This cleanup is
+  // not guaranteed to handle trees/cycles of PHI nodes that only are used by
+  // each other. Such situations has only been noticed when the input IR
+  // contains unreachable code, and leaving some extra redundant PHI nodes in
+  // such situations is considered a minor problem.
+  for (PHINode *PN : PHIsToRemove)
+    if (PN->use_empty())
+      PN->eraseFromParent();
   return Changed;
 }