[llvm] r324247 - Revert r323472 "[Debug] Add dbg.value intrinsics for PHIs created during LCSSA."

[Hans Wennborg via llvm-commits]

Author: hans
Date: Mon Feb  5 08:10:42 2018
New Revision: 324247

URL: http://llvm.org/viewvc/llvm-project?rev=324247&view=rev
Log:
Revert r323472 "[Debug] Add dbg.value intrinsics for PHIs created during LCSSA."

This broke the Chromium build; see PR36238.

> This patch is an enhancement to propagate dbg.value information when
> Phis are created on behalf of LCSSA.  I noticed a case where a value
> carried across a loop was reported as <optimized out>.
>
> Specifically this case:
>
>   int bar(int x, int y) {
>     return x + y;
>   }
>
>   int foo(int size) {
>     int val = 0;
>     for (int i = 0; i < size; ++i) {
>       val = bar(val, i);  // Both val and i are correct
>     }
>     return val; // <optimized out>
>   }
>
> In the above case, after all of the interesting computation completes
> our value is reported as "optimized out." This change will add a
> dbg.value to correct this.
>
> This patch also moves the dbg.value insertion routine from
> LoopRotation.cpp into Local.cpp, so that we can share it in both places
> (LoopRotation and LCSSA).
>
> Patch by Matt Davis!
>
> Differential Revision: https://reviews.llvm.org/D42551

Modified:
    llvm/trunk/lib/Transforms/Utils/LCSSA.cpp
    llvm/trunk/test/Transforms/LCSSA/basictest.ll

Modified: llvm/trunk/lib/Transforms/Utils/LCSSA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LCSSA.cpp?rev=324247&r1=324246&r2=324247&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LCSSA.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LCSSA.cpp Mon Feb  5 08:10:42 2018
@@ -43,7 +43,6 @@
 #include "llvm/IR/PredIteratorCache.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/SSAUpdater.h"
 using namespace llvm;
@@ -215,15 +214,11 @@ bool llvm::formLCSSAForInstructions(Smal
         Worklist.push_back(PostProcessPN);
 
     // Keep track of PHI nodes that we want to remove because they did not have
-    // any uses rewritten. If the new PHI is used, store it so that we can
-    // try to propagate dbg.value intrinsics to it.
-    SmallVector<PHINode *, 2> NeedDbgValues;
+    // any uses rewritten.
     for (PHINode *PN : AddedPHIs)
       if (PN->use_empty())
         PHIsToRemove.insert(PN);
-      else
-        NeedDbgValues.push_back(PN);
-    insertDebugValuesForPHIs(InstBB, NeedDbgValues);
+
     Changed = true;
   }
   // Remove PHI nodes that did not have any uses rewritten.

Modified: llvm/trunk/test/Transforms/LCSSA/basictest.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LCSSA/basictest.ll?rev=324247&r1=324246&r2=324247&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LCSSA/basictest.ll (original)
+++ llvm/trunk/test/Transforms/LCSSA/basictest.ll Mon Feb  5 08:10:42 2018
@@ -1,6 +1,5 @@
 ; RUN: opt < %s -lcssa -S | FileCheck %s
 ; RUN: opt < %s -passes=lcssa -S | FileCheck %s
-; RUN: opt < %s -debugify -lcssa -S | FileCheck -check-prefix=CHECK2 %s
 
 define void @lcssa(i1 %S2) {
 ; CHECK-LABEL: @lcssa