[Debugify] Add a pass to test debug info preservation

The Debugify pass synthesizes debug info for IR. It's paired with a
CheckDebugify pass which determines how much of the original debug info
is preserved. These passes make it easier to create targeted tests for
debug info preservation.

Here is the Debugify algorithm:

  NextLine = 1
  for (Instruction &I : M)
    attach DebugLoc(NextLine++) to I

  NextVar = 1
  for (Instruction &I : M)
    if (canAttachDebugValue(I))
      attach dbg.value(NextVar++) to I

The CheckDebugify pass expects contiguous ranges of DILocations and
DILocalVariables. If it fails to find all of the expected debug info, it
prints a specific error to stderr which can be FileChecked.

This was discussed on llvm-dev in the thread:
"Passes to add/validate synthetic debug info"

Differential Revision: https://reviews.llvm.org/D40512

llvm-svn: 320202

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/test/Transforms/Mem2Reg/PromoteMemToRegister.ll b/llvm/test/Transforms/Mem2Reg/PromoteMemToRegister.ll
index b7f39947afb..a15be3854db 100644
--- a/llvm/test/Transforms/Mem2Reg/PromoteMemToRegister.ll
+++ b/llvm/test/Transforms/Mem2Reg/PromoteMemToRegister.ll
@@ -1,5 +1,8 @@
 ; Simple sanity check testcase.  Both alloca's should be eliminated.
-; RUN: opt < %s -mem2reg -S | not grep alloca
+; RUN: opt < %s -debugify -mem2reg -check-debugify -S | FileCheck %s
+
+; CHECK-NOT: alloca
+; CHECK: CheckDebugify: PASS
 
 define double @testfunc(i32 %i, double %j) {
 	%I = alloca i32		; <i32*> [#uses=4]