[WinEH] Add and use hasEHPadSuccessor instead of getLandingPadSuccessor

getLandingPadSuccessor assumes that each invoke can have at most one EH
pad successor, but WinEH invokes can have more than one. Two out of
three callers of getLandingPadSuccessor don't use the returned
landingpad, so we can make them use this simple predicate instead.

Eventually we'll have to circle back and fix SplitKit.cpp so that
register allocation works. Baby steps.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247904 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineBasicBlock.h

@@ -381,6 +381,8 @@ public:
   /// return NULL.
   const MachineBasicBlock *getLandingPadSuccessor() const;
 
+  bool hasEHPadSuccessor() const;
+
   /// Returns true if this is the entry block of an EH funclet.
   bool isEHFuncletEntry() const { return IsEHFuncletEntry; }
 

lib/CodeGen/BranchFolding.cpp

@@ -976,7 +976,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
         continue;
 
       // Skip blocks which may jump to a landing pad. Can't tail merge these.
-      if (PBB->getLandingPadSuccessor())
+      if (PBB->hasEHPadSuccessor())
         continue;
 
       MachineBasicBlock *TBB = nullptr, *FBB = nullptr;

lib/CodeGen/MachineBasicBlock.cpp

@@ -208,6 +208,13 @@ const MachineBasicBlock *MachineBasicBlock::getLandingPadSuccessor() const {
   return nullptr;
 }
 
+bool MachineBasicBlock::hasEHPadSuccessor() const {
+  for (const_succ_iterator I = succ_begin(), E = succ_end(); I != E; ++I)
+    if ((*I)->isEHPad())
+      return true;
+  return false;
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void MachineBasicBlock::dump() const {
   print(dbgs());

lib/CodeGen/SplitKit.cpp

@@ -56,6 +56,7 @@ void SplitAnalysis::clear() {
 
 SlotIndex SplitAnalysis::computeLastSplitPoint(unsigned Num) {
   const MachineBasicBlock *MBB = MF.getBlockNumbered(Num);
+  // FIXME: Handle multiple EH pad successors.
   const MachineBasicBlock *LPad = MBB->getLandingPadSuccessor();
   std::pair<SlotIndex, SlotIndex> &LSP = LastSplitPoint[Num];
   SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);

lib/CodeGen/TailDuplication.cpp

@@ -673,7 +673,7 @@ TailDuplicatePass::duplicateSimpleBB(MachineBasicBlock *TailBB,
        PE = Preds.end(); PI != PE; ++PI) {
     MachineBasicBlock *PredBB = *PI;
 
-    if (PredBB->getLandingPadSuccessor())
+    if (PredBB->hasEHPadSuccessor())
       continue;
 
     if (bothUsedInPHI(*PredBB, Succs))

test/CodeGen/X86/tail-merge-wineh.ll

@@ -0,0 +1,116 @@
+; RUN: llc < %s | FileCheck %s
+
+; Started from this code:
+; void f() {
+;   try {
+;     try {
+;       throw 42;
+;     } catch (int) {
+;     }
+;     try {
+;       throw 42;
+;     } catch (int) {
+;     }
+;   } catch (int) {
+;   }
+; }
+
+; Don't tail merge the calls.
+; CHECK: calll _CxxThrowException
+; CHECK: calll _CxxThrowException
+
+; ModuleID = 'cppeh-pingpong.cpp'
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc"
+
+%rtti.TypeDescriptor2 = type { i8**, i8*, [3 x i8] }
+%eh.CatchableType = type { i32, i8*, i32, i32, i32, i32, i8* }
+%eh.CatchableTypeArray.1 = type { i32, [1 x %eh.CatchableType*] }
+%eh.ThrowInfo = type { i32, i8*, i8*, i8* }
+
+$"\01??_R0H@8" = comdat any
+
+$"_CT??_R0H@84" = comdat any
+
+$_CTA1H = comdat any
+
+$_TI1H = comdat any
+
+@"\01??_7type_info@@6B@" = external constant i8*
+@"\01??_R0H@8" = linkonce_odr global %rtti.TypeDescriptor2 { i8** @"\01??_7type_info@@6B@", i8* null, [3 x i8] c".H\00" }, comdat
+@"_CT??_R0H@84" = linkonce_odr unnamed_addr constant %eh.CatchableType { i32 1, i8* bitcast (%rtti.TypeDescriptor2* @"\01??_R0H@8" to i8*), i32 0, i32 -1, i32 0, i32 4, i8* null }, section ".xdata", comdat
+@_CTA1H = linkonce_odr unnamed_addr constant %eh.CatchableTypeArray.1 { i32 1, [1 x %eh.CatchableType*] [%eh.CatchableType* @"_CT??_R0H@84"] }, section ".xdata", comdat
+@_TI1H = linkonce_odr unnamed_addr constant %eh.ThrowInfo { i32 0, i8* null, i8* null, i8* bitcast (%eh.CatchableTypeArray.1* @_CTA1H to i8*) }, section ".xdata", comdat
+
+define void @"\01?f@@YAXXZ"() #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %i = alloca i32, align 4
+  %tmp = alloca i32, align 4
+  %tmp1 = alloca i32, align 4
+  store i32 0, i32* %i, align 4
+  store i32 42, i32* %tmp, align 4
+  %0 = bitcast i32* %tmp to i8*
+  invoke void @_CxxThrowException(i8* %0, %eh.ThrowInfo* @_TI1H) #1
+          to label %unreachable unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %1 = catchpad [%rtti.TypeDescriptor2* @"\01??_R0H@8", i32 0, i8* null]
+          to label %catch unwind label %catchendblock
+
+catch:                                            ; preds = %catch.dispatch
+  catchret %1 to label %catchret.dest
+
+catchret.dest:                                    ; preds = %catch
+  br label %try.cont
+
+try.cont:                                         ; preds = %catchret.dest
+  store i32 42, i32* %tmp1, align 4
+  %2 = bitcast i32* %tmp1 to i8*
+  invoke void @_CxxThrowException(i8* %2, %eh.ThrowInfo* @_TI1H) #1
+          to label %unreachable unwind label %catch.dispatch.2
+
+catch.dispatch.2:                                 ; preds = %try.cont
+  %3 = catchpad [%rtti.TypeDescriptor2* @"\01??_R0H@8", i32 0, i8* null]
+          to label %catch.4 unwind label %catchendblock.3
+
+catch.4:                                          ; preds = %catch.dispatch.2
+  catchret %3 to label %catchret.dest.5
+
+catchret.dest.5:                                  ; preds = %catch.4
+  br label %try.cont.6
+
+try.cont.6:                                       ; preds = %catchret.dest.5
+  br label %try.cont.11
+
+catchendblock.3:                                  ; preds = %catch.dispatch.2
+  catchendpad unwind label %catch.dispatch.7
+
+catch.dispatch.7:                                 ; preds = %catchendblock.3, %catchendblock
+  %4 = catchpad [%rtti.TypeDescriptor2* @"\01??_R0H@8", i32 0, i8* null]
+          to label %catch.9 unwind label %catchendblock.8
+
+catch.9:                                          ; preds = %catch.dispatch.7
+  catchret %4 to label %catchret.dest.10
+
+catchret.dest.10:                                 ; preds = %catch.9
+  br label %try.cont.11
+
+try.cont.11:                                      ; preds = %catchret.dest.10, %try.cont.6
+  ret void
+
+catchendblock.8:                                  ; preds = %catch.dispatch.7
+  catchendpad unwind to caller
+
+catchendblock:                                    ; preds = %catch.dispatch
+  catchendpad unwind label %catch.dispatch.7
+
+unreachable:                                      ; preds = %try.cont, %entry
+  unreachable
+}
+
+declare x86_stdcallcc void @_CxxThrowException(i8*, %eh.ThrowInfo*)
+
+declare i32 @__CxxFrameHandler3(...)
+
+attributes #0 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { noreturn }