From 4f55de6f81339a76c4eda767234952da1086dd52 Mon Sep 17 00:00:00 2001
From: Vedant Kumar <vsk@apple.com>
Date: Mon, 4 Jun 2018 03:33:01 +0000
Subject: [PATCH] [Debugify] Add debug intrinsics before terminating musttail
 calls

After r333856, opt -debugify would just stop emitting debug value
intrinsics after encountering a musttail call. This wasn't sufficient to
avoid verifier failures.

Debug value intrinicss for all instructions preceding a musttail call
must also be emitted before the musttail call.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333866 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/Transforms/InstCombine/musttail-thunk.ll |  1 +
 tools/opt/Debugify.cpp                        | 22 +++++++++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/test/Transforms/InstCombine/musttail-thunk.ll b/test/Transforms/InstCombine/musttail-thunk.ll
index 4038aa525a5..2e8e3a7b9c2 100644
--- a/test/Transforms/InstCombine/musttail-thunk.ll
+++ b/test/Transforms/InstCombine/musttail-thunk.ll
@@ -1,4 +1,5 @@
 ; RUN: opt -instcombine -S < %s | FileCheck %s
+; RUN: opt -debugify-each -instcombine -S < %s | FileCheck %s
 
 ; These are both direct calls, but make sure instcombine leaves the casts
 ; alone.
diff --git a/tools/opt/Debugify.cpp b/tools/opt/Debugify.cpp
index f26a95f2ba1..0a900a520ab 100644
--- a/tools/opt/Debugify.cpp
+++ b/tools/opt/Debugify.cpp
@@ -91,28 +91,32 @@ bool applyDebugifyMetadata(Module &M,
       if (BB.isEHPad())
         continue;
 
+      // Debug values must be inserted before a musttail call (if one is
+      // present), or before the block terminator otherwise.
+      Instruction *LastInst = BB.getTerminatingMustTailCall();
+      if (!LastInst)
+        LastInst = BB.getTerminator();
+
       // Attach debug values.
-      for (Instruction &I : BB) {
+      for (auto It = BB.begin(), End = LastInst->getIterator(); It != End;
+           ++It) {
+        Instruction &I = *It;
+
         // Skip void-valued instructions.
         if (I.getType()->isVoidTy())
           continue;
 
-        // Skip the terminator instruction and any just-inserted intrinsics.
-        if (isa<TerminatorInst>(&I) || isa<DbgValueInst>(&I))
+        // Skip any just-inserted intrinsics.
+        if (isa<DbgValueInst>(&I))
           break;
 
-        // Don't insert instructions after a musttail call.
-        if (auto *Call = dyn_cast<CallInst>(&I))
-          if (Call->isMustTailCall())
-            break;
-
         std::string Name = utostr(NextVar++);
         const DILocation *Loc = I.getDebugLoc().get();
         auto LocalVar = DIB.createAutoVariable(SP, Name, File, Loc->getLine(),
                                                getCachedDIType(I.getType()),
                                                /*AlwaysPreserve=*/true);
         DIB.insertDbgValueIntrinsic(&I, LocalVar, DIB.createExpression(), Loc,
-                                    BB.getTerminator());
+                                    LastInst);
       }
     }
     DIB.finalizeSubprogram(SP);
-- 
2.11.0