1 files changed, 14 insertions, 48 deletions

diff --git a/llvm/lib/CodeGen/StackColoring.cpp b/llvm/lib/CodeGen/StackColoring.cpp
index 66b9086e1d88..3453b718b453 100644
--- a/llvm/lib/CodeGen/StackColoring.cpp
+++ b/llvm/lib/CodeGen/StackColoring.cpp
@@ -370,37 +370,6 @@ STATISTIC(EscapedAllocas, "Number of allocas that escaped the lifetime region");
 // If in RPO ordering chosen to walk the CFG  we happen to visit the b[k]
 // before visiting the memcpy block (which will contain the lifetime start
 // for "b" then it will appear that 'b' has a degenerate lifetime.
-//
-// Handle Windows Exception with LifetimeStartOnFirstUse:
-// -----------------
-//
-// There was a bug for using LifetimeStartOnFirstUse in win32.
-// class Type1 {
-// ...
-// ~Type1(){ write memory;}
-// }
-// ...
-// try{
-// Type1 V
-// ...
-// } catch (Type2 X){
-// ...
-// }
-// For variable X in catch(X), we put point pX=&(&X) into ConservativeSlots
-// to prevent using LifetimeStartOnFirstUse. Because pX may merged with
-// object V which may call destructor after implicitly writing pX. All these
-// are done in C++ EH runtime libs (through CxxThrowException), and can't
-// obviously check it in IR level.
-//
-// The loader of pX, without obvious writing IR, is usually the first LOAD MI
-// in EHPad, Some like:
-// bb.x.catch.i (landing-pad, ehfunclet-entry):
-// ; predecessors: %bb...
-//   successors: %bb...
-//  %n:gr32 = MOV32rm %stack.pX ...
-//  ...
-// The Type2** %stack.pX will only be written in EH runtime libs, so we
-// check the StoreSlots to screen it out.
 
 namespace {
 
@@ -462,9 +431,6 @@ class StackColoring : public MachineFunctionPass {
   /// slots lifetime-start-on-first-use is disabled).
   BitVector ConservativeSlots;
 
-  /// Record the FI slots referenced by a 'may write to memory'.
-  BitVector StoreSlots;
-
   /// Number of iterations taken during data flow analysis.
   unsigned NumIterations;
 
@@ -660,13 +626,10 @@ unsigned StackColoring::collectMarkers(unsigned NumSlot) {
   InterestingSlots.resize(NumSlot);
   ConservativeSlots.clear();
   ConservativeSlots.resize(NumSlot);
-  StoreSlots.clear();
-  StoreSlots.resize(NumSlot);
 
   // number of start and end lifetime ops for each slot
   SmallVector<int, 8> NumStartLifetimes(NumSlot, 0);
   SmallVector<int, 8> NumEndLifetimes(NumSlot, 0);
-  SmallVector<int, 8> NumLoadInCatchPad(NumSlot, 0);
 
   // Step 1: collect markers and populate the "InterestingSlots"
   // and "ConservativeSlots" sets.
@@ -722,13 +685,6 @@ unsigned StackColoring::collectMarkers(unsigned NumSlot) {
           if (! BetweenStartEnd.test(Slot)) {
             ConservativeSlots.set(Slot);
           }
-          // Here we check the StoreSlots to screen catch point out. For more
-          // information, please refer "Handle Windows Exception with
-          // LifetimeStartOnFirstUse" at the head of this file.
-          if (MI.mayStore())
-            StoreSlots.set(Slot);
-          if (MF->getWinEHFuncInfo() && MBB->isEHPad() && MI.mayLoad())
-            NumLoadInCatchPad[Slot] += 1;
         }
       }
     }
@@ -739,14 +695,24 @@ unsigned StackColoring::collectMarkers(unsigned NumSlot) {
     return 0;
   }
 
-  // 1) PR27903: slots with multiple start or end lifetime ops are not
+  // PR27903: slots with multiple start or end lifetime ops are not
   // safe to enable for "lifetime-start-on-first-use".
-  // 2) And also not safe for variable X in catch(X) in windows.
   for (unsigned slot = 0; slot < NumSlot; ++slot) {
-    if (NumStartLifetimes[slot] > 1 || NumEndLifetimes[slot] > 1 ||
-        (NumLoadInCatchPad[slot] > 1 && !StoreSlots.test(slot)))
+    if (NumStartLifetimes[slot] > 1 || NumEndLifetimes[slot] > 1)
       ConservativeSlots.set(slot);
   }
+
+  // The write to the catch object by the personality function is not propely
+  // modeled in IR: It happens before any cleanuppads are executed, even if the
+  // first mention of the catch object is in a catchpad. As such, mark catch
+  // object slots as conservative, so they are excluded from first-use analysis.
+  if (WinEHFuncInfo *EHInfo = MF->getWinEHFuncInfo())
+    for (WinEHTryBlockMapEntry &TBME : EHInfo->TryBlockMap)
+      for (WinEHHandlerType &H : TBME.HandlerArray)
+        if (H.CatchObj.FrameIndex != std::numeric_limits<int>::max() &&
+            H.CatchObj.FrameIndex >= 0)
+          ConservativeSlots.set(H.CatchObj.FrameIndex);
+
   LLVM_DEBUG(dumpBV("Conservative slots", ConservativeSlots));
 
   // Step 2: compute begin/end sets for each block