Re-revert: Recover debug intrinsics when killing duplicated/empty blocks

This reverts commit 61b35e4111160fe834a00c33d040e01150b576ac.

This commit causes a timeout in chromium builds; likely to have a
similar cause to the previous timeout issue caused by this commit (see
6ded69f294a9 for more details). It is possible that there is no way to
fix this bug that will not cause this issue; further investigations as
to the efficiency of handling large amounts of debug info will be
necessary.

1 files changed, 17 insertions, 42 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 0f8a9b4..222f8af 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -13,7 +13,6 @@
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetOperations.h"
@@ -39,7 +38,6 @@
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
-#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
@@ -1252,38 +1250,14 @@ static bool HoistThenElseCodeToIf(BranchInst *BI,
 
   Instruction *I1 = &*BB1_Itr++, *I2 = &*BB2_Itr++;
   // Skip debug info if it is not identical.
-
-  // If the terminator instruction is hoisted, and any variable locations have
-  // non-identical debug intrinsics, then those variable locations must be set
-  // as undef.
-  // FIXME: If each block contains identical debug variable intrinsics in a
-  // different order, they will be considered non-identical and be dropped.
-  MapVector<DebugVariable, DbgVariableIntrinsic *> UndefDVIs;
-
-  auto SkipDbgInfo = [&UndefDVIs](Instruction *&I,
-                                  BasicBlock::iterator &BB_Itr) {
-    while (isa<DbgInfoIntrinsic>(I)) {
-      if (DbgVariableIntrinsic *DVI = dyn_cast<DbgVariableIntrinsic>(I))
-        UndefDVIs.insert(
-            {DebugVariable(DVI->getVariable(), DVI->getExpression(),
-                           DVI->getDebugLoc()->getInlinedAt()),
-             DVI});
-      I = &*BB_Itr++;
-    }
-  };
-
-  auto SkipNonIdenticalDbgInfo =
-      [&BB1_Itr, &BB2_Itr, &SkipDbgInfo](Instruction *&I1, Instruction *&I2) {
-        DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
-        DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
-        if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
-          SkipDbgInfo(I1, BB1_Itr);
-          SkipDbgInfo(I2, BB2_Itr);
-        }
-      };
-
-  SkipNonIdenticalDbgInfo(I1, I2);
-
+  DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
+  DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
+  if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
+    while (isa<DbgInfoIntrinsic>(I1))
+      I1 = &*BB1_Itr++;
+    while (isa<DbgInfoIntrinsic>(I2))
+      I2 = &*BB2_Itr++;
+  }
   // FIXME: Can we define a safety predicate for CallBr?
   if (isa<PHINode>(I1) || !I1->isIdenticalToWhenDefined(I2) ||
       (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)) ||
@@ -1356,7 +1330,15 @@ static bool HoistThenElseCodeToIf(BranchInst *BI,
 
     I1 = &*BB1_Itr++;
     I2 = &*BB2_Itr++;
-    SkipNonIdenticalDbgInfo(I1, I2);
+    // Skip debug info if it is not identical.
+    DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
+    DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
+    if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
+      while (isa<DbgInfoIntrinsic>(I1))
+        I1 = &*BB1_Itr++;
+      while (isa<DbgInfoIntrinsic>(I2))
+        I2 = &*BB2_Itr++;
+    }
   } while (I1->isIdenticalToWhenDefined(I2));
 
   return true;
@@ -1392,13 +1374,6 @@ HoistTerminator:
   }
 
   // Okay, it is safe to hoist the terminator.
-  for (auto DIVariableInst : UndefDVIs) {
-    DbgVariableIntrinsic *DVI = DIVariableInst.second;
-    DVI->moveBefore(BI);
-    if (DVI->getVariableLocation())
-      setDbgVariableUndef(DVI);
-  }
-
   Instruction *NT = I1->clone();
   BIParent->getInstList().insert(BI->getIterator(), NT);
   if (!NT->getType()->isVoidTy()) {