From 5aa3fa6d827e162893534454b2a2c4b6e50884fc Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Tue, 8 Mar 2011 22:12:11 +0000
Subject: [PATCH] llvm.dbg.declare intrinsic does not use any llvm::Values.
 It's magic!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127282 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/InstCombine/InstCombine.h      |  1 -
 .../InstCombine/InstCombineCasts.cpp          | 13 ++------
 .../InstCombineLoadStoreAlloca.cpp            | 30 -------------------
 3 files changed, 3 insertions(+), 41 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombine.h b/lib/Transforms/InstCombine/InstCombine.h
index 9c2969c7ab2..0da962a5f40 100644
--- a/lib/Transforms/InstCombine/InstCombine.h
+++ b/lib/Transforms/InstCombine/InstCombine.h
@@ -218,7 +218,6 @@ private:
   Instruction *transformZExtICmp(ICmpInst *ICI, Instruction &CI,
                                  bool DoXform = true);
   bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS);
-  DbgDeclareInst *hasOneUsePlusDeclare(Value *V);
   Value *EmitGEPOffset(User *GEP);
 
 public:
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index b432641a140..dcf7be1a91a 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -87,10 +87,8 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
 
   // If the allocation has multiple uses, only promote it if we are strictly
   // increasing the alignment of the resultant allocation.  If we keep it the
-  // same, we open the door to infinite loops of various kinds.  (A reference
-  // from a dbg.declare doesn't count as a use for this purpose.)
-  if (!AI.hasOneUse() && !hasOneUsePlusDeclare(&AI) &&
-      CastElTyAlign == AllocElTyAlign) return 0;
+  // same, we open the door to infinite loops of various kinds.
+  if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0;
 
   uint64_t AllocElTySize = TD->getTypeAllocSize(AllocElTy);
   uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy);
@@ -128,15 +126,10 @@ Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
   New->setAlignment(AI.getAlignment());
   New->takeName(&AI);
   
-  // If the allocation has one real use plus a dbg.declare, just remove the
-  // declare.
-  if (DbgDeclareInst *DI = hasOneUsePlusDeclare(&AI)) {
-    EraseInstFromFunction(*(Instruction*)DI);
-  }
   // If the allocation has multiple real uses, insert a cast and change all
   // things that used it to use the new cast.  This will also hack on CI, but it
   // will die soon.
-  else if (!AI.hasOneUse()) {
+  if (!AI.hasOneUse()) {
     // New is the allocation instruction, pointer typed. AI is the original
     // allocation instruction, also pointer typed. Thus, cast to use is BitCast.
     Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast");
diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index 78ff7346abe..35c1d91d501 100644
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -364,34 +364,12 @@ static bool equivalentAddressValues(Value *A, Value *B) {
   return false;
 }
 
-// If this instruction has two uses, one of which is a llvm.dbg.declare,
-// return the llvm.dbg.declare.
-DbgDeclareInst *InstCombiner::hasOneUsePlusDeclare(Value *V) {
-  if (!V->hasNUses(2))
-    return 0;
-  for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
-       UI != E; ++UI) {
-    User *U = *UI;
-    if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(U))
-      return DI;
-    if (isa<BitCastInst>(U) && U->hasOneUse()) {
-      if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(*U->use_begin()))
-        return DI;
-      }
-  }
-  return 0;
-}
-
 Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
   Value *Val = SI.getOperand(0);
   Value *Ptr = SI.getOperand(1);
 
   // If the RHS is an alloca with a single use, zapify the store, making the
   // alloca dead.
-  // If the RHS is an alloca with a two uses, the other one being a 
-  // llvm.dbg.declare, zapify the store and the declare, making the
-  // alloca dead.  We must do this to prevent declares from affecting
-  // codegen.
   if (!SI.isVolatile()) {
     if (Ptr->hasOneUse()) {
       if (isa<AllocaInst>(Ptr)) 
@@ -400,17 +378,9 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
         if (isa<AllocaInst>(GEP->getOperand(0))) {
           if (GEP->getOperand(0)->hasOneUse())
             return EraseInstFromFunction(SI);
-          if (DbgDeclareInst *DI = hasOneUsePlusDeclare(GEP->getOperand(0))) {
-            EraseInstFromFunction(*DI);
-            return EraseInstFromFunction(SI);
-          }
         }
       }
     }
-    if (DbgDeclareInst *DI = hasOneUsePlusDeclare(Ptr)) {
-      EraseInstFromFunction(*DI);
-      return EraseInstFromFunction(SI);
-    }
   }
 
   // Attempt to improve the alignment.
-- 
2.34.1