patch to update the line number information in pass -mem2reg.

Currently this pass will delete the variable declaration info, 
and keep the line number info. But the kept line number info is not updated, 
and some is redundant or not correct, this patch just updates those info.

llvm-svn: 65123

llvm/lib/Transforms/Utils/Mem2Reg.cpp

@@ -16,6 +16,7 @@
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
+#include "llvm/IntrinsicInst.h"
 #include "llvm/Analysis/Dominators.h"
 #include "llvm/Instructions.h"
 #include "llvm/Function.h"
@@ -53,6 +54,30 @@ namespace {
 char PromotePass::ID = 0;
 static RegisterPass<PromotePass> X("mem2reg", "Promote Memory to Register");
 
+/// Remove the invalid or redundant debug information.
+static void CleanDbgInfo(Function& F) {
+  std::vector<Instruction*> DeadDbgs;
+  for (Function::iterator BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
+    if (BBI->size() <= 1)
+      continue;
+    for (BasicBlock::iterator I = BBI->begin(), E = BBI->getTerminator(); 
+         I != E; ++I) {
+      BasicBlock::iterator NextI = I;
+      ++NextI;
+      if (isa<DbgStopPointInst>(I) && isa<DbgStopPointInst>(NextI))
+        DeadDbgs.push_back(I);
+      else if (isa<DbgStopPointInst>(I) && isa<BranchInst>(NextI))
+        DeadDbgs.push_back(I);
+    }
+  }
+
+  while (!DeadDbgs.empty()) {
+    Instruction *Inst = DeadDbgs.back();
+    DeadDbgs.pop_back();
+    Inst->eraseFromParent();
+  }
+}
+
 bool PromotePass::runOnFunction(Function &F) {
   std::vector<AllocaInst*> Allocas;
 
@@ -76,6 +101,7 @@ bool PromotePass::runOnFunction(Function &F) {
     if (Allocas.empty()) break;
 
     PromoteMemToReg(Allocas, DT, DF);
+    CleanDbgInfo(F);
     NumPromoted += Allocas.size();
     Changed = true;
   }