Patch to fix pragma metadata for do-while loops

Summary:
Make sure that loop metadata only is put on the backedge
when expanding a do-while loop.
Previously we added the loop metadata also on the branch
in the pre-header. That could confuse optimization passes
and result in the loop metadata being associated with the
wrong loop.

Fixes https://bugs.llvm.org/show_bug.cgi?id=38011

Committing on behalf of deepak2427 (Deepak Panickal)

Reviewers: #clang, ABataev, hfinkel, aaron.ballman, bjope

Reviewed By: bjope

Subscribers: bjope, rsmith, shenhan, zzheng, xbolva00, lebedev.ri, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D48721

llvm-svn: 336717
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index 779bda6..79662ec 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -777,11 +777,6 @@
   // Emit the body of the loop.
   llvm::BasicBlock *LoopBody = createBasicBlock("do.body");
 
-  const SourceRange &R = S.getSourceRange();
-  LoopStack.push(LoopBody, CGM.getContext(), DoAttrs,
-                 SourceLocToDebugLoc(R.getBegin()),
-                 SourceLocToDebugLoc(R.getEnd()));
-
   EmitBlockWithFallThrough(LoopBody, &S);
   {
     RunCleanupsScope BodyScope(*this);
@@ -790,6 +785,11 @@
 
   EmitBlock(LoopCond.getBlock());
 
+  const SourceRange &R = S.getSourceRange();
+  LoopStack.push(LoopBody, CGM.getContext(), DoAttrs,
+                 SourceLocToDebugLoc(R.getBegin()),
+                 SourceLocToDebugLoc(R.getEnd()));
+
   // C99 6.8.5.2: "The evaluation of the controlling expression takes place
   // after each execution of the loop body."