[SEH] Remove CATCHPAD SDNode and X86::EH_RESTORE MachineInstr

The CATCHPAD node mostly existed to be selected into the EH_RESTORE
instruction, which sets the frame back up when 32-bit Windows exceptions
return to the parent function. However, creating this MachineInstr early
increases the risk that other passes will come along and insert
instructions that use the stack before ESP and EBP are restored. That
happened in PR44697.

Instead of representing these in the instruction stream early, delay it
until PEI. Mark the blocks where this needs to happen as EHPads, but not
funclet entry blocks. Passes after PEI have to be careful not to hoist
instructions that can use stack across frame setup instructions, so this
should be relatively reliable.

Fixes PR44697

Reviewed By: hans

Differential Revision: https://reviews.llvm.org/D73752

diff --git a/llvm/include/llvm/CodeGen/ISDOpcodes.h b/llvm/include/llvm/CodeGen/ISDOpcodes.h
index 2e447cf..b5a434b 100644 (file)
--- a/llvm/include/llvm/CodeGen/ISDOpcodes.h
+++ b/llvm/include/llvm/CodeGen/ISDOpcodes.h
@@ -738,9 +738,6 @@ namespace ISD {
     /// past it.
     ANNOTATION_LABEL,
 
-    /// CATCHPAD - Represents a catchpad instruction.
-    CATCHPAD,
-
     /// CATCHRET - Represents a return from a catch block funclet. Used for
     /// MSVC compatible exception handling. Takes a chain operand and a
     /// destination basic block operand.

diff --git a/llvm/include/llvm/Target/TargetSelectionDAG.td b/llvm/include/llvm/Target/TargetSelectionDAG.td
index 1f3ea15..7d8b970 100644 (file)
--- a/llvm/include/llvm/Target/TargetSelectionDAG.td
+++ b/llvm/include/llvm/Target/TargetSelectionDAG.td
@@ -564,8 +564,6 @@ def br         : SDNode<"ISD::BR"         , SDTBr,     [SDNPHasChain]>;
 def catchret   : SDNode<"ISD::CATCHRET"   , SDTCatchret,
                         [SDNPHasChain, SDNPSideEffect]>;
 def cleanupret : SDNode<"ISD::CLEANUPRET" , SDTNone,   [SDNPHasChain]>;
-def catchpad   : SDNode<"ISD::CATCHPAD"   , SDTNone,
-                        [SDNPHasChain, SDNPSideEffect]>;
 
 def trap       : SDNode<"ISD::TRAP"       , SDTNone,
                         [SDNPHasChain, SDNPSideEffect]>;

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 84c8a8f..fc88e5f 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1615,17 +1615,12 @@ void SelectionDAGBuilder::visitCatchPad(const CatchPadInst &I) {
   bool IsMSVCCXX = Pers == EHPersonality::MSVC_CXX;
   bool IsCoreCLR = Pers == EHPersonality::CoreCLR;
   bool IsSEH = isAsynchronousEHPersonality(Pers);
-  bool IsWasmCXX = Pers == EHPersonality::Wasm_CXX;
   MachineBasicBlock *CatchPadMBB = FuncInfo.MBB;
   if (!IsSEH)
     CatchPadMBB->setIsEHScopeEntry();
   // In MSVC C++ and CoreCLR, catchblocks are funclets and need prologues.
   if (IsMSVCCXX || IsCoreCLR)
     CatchPadMBB->setIsEHFuncletEntry();
-  // Wasm does not need catchpads anymore
-  if (!IsWasmCXX)
-    DAG.setRoot(DAG.getNode(ISD::CATCHPAD, getCurSDLoc(), MVT::Other,
-                            getControlRoot()));
 }
 
 void SelectionDAGBuilder::visitCatchRet(const CatchReturnInst &I) {

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 37ff61c..004314a 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -1497,12 +1497,6 @@ MachineBasicBlock *AArch64TargetLowering::EmitLoweredCatchRet(
   return BB;
 }
 
-MachineBasicBlock *AArch64TargetLowering::EmitLoweredCatchPad(
-     MachineInstr &MI, MachineBasicBlock *BB) const {
-  MI.eraseFromParent();
-  return BB;
-}
-
 MachineBasicBlock *AArch64TargetLowering::EmitInstrWithCustomInserter(
     MachineInstr &MI, MachineBasicBlock *BB) const {
   switch (MI.getOpcode()) {
@@ -1521,8 +1515,6 @@ MachineBasicBlock *AArch64TargetLowering::EmitInstrWithCustomInserter(
 
   case AArch64::CATCHRET:
     return EmitLoweredCatchRet(MI, BB);
-  case AArch64::CATCHPAD:
-    return EmitLoweredCatchPad(MI, BB);
   }
 }
 

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.h b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
index 5b95971..363302c 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -386,9 +386,6 @@ public:
   MachineBasicBlock *EmitLoweredCatchRet(MachineInstr &MI,
                                            MachineBasicBlock *BB) const;
 
-  MachineBasicBlock *EmitLoweredCatchPad(MachineInstr &MI,
-                                         MachineBasicBlock *BB) const;
-
   MachineBasicBlock *
   EmitInstrWithCustomInserter(MachineInstr &MI,
                               MachineBasicBlock *MBB) const override;

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 1938c6f..67c7039 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -3628,10 +3628,6 @@ let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
                     Sched<[]>;
 }
 
-let hasSideEffects = 1, hasCtrlDep = 1, isCodeGenOnly = 1,
-    usesCustomInserter = 1 in
-def CATCHPAD : Pseudo<(outs), (ins), [(catchpad)]>, Sched<[]>;
-
 //===----------------------------------------------------------------------===//
 // Floating point immediate move.
 //===----------------------------------------------------------------------===//

diff --git a/llvm/lib/Target/X86/X86ExpandPseudo.cpp b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
index d35d659..3e50de4 100644 (file)
--- a/llvm/lib/Target/X86/X86ExpandPseudo.cpp
+++ b/llvm/lib/Target/X86/X86ExpandPseudo.cpp
@@ -331,14 +331,6 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
     MBB.erase(MBBI);
     return true;
   }
-  case X86::EH_RESTORE: {
-    // Restore ESP and EBP, and optionally ESI if required.
-    bool IsSEH = isAsynchronousEHPersonality(classifyEHPersonality(
-        MBB.getParent()->getFunction().getPersonalityFn()));
-    X86FL->restoreWin32EHStackPointers(MBB, MBBI, DL, /*RestoreSP=*/IsSEH);
-    MBBI->eraseFromParent();
-    return true;
-  }
   case X86::LCMPXCHG8B_SAVE_EBX:
   case X86::LCMPXCHG16B_SAVE_RBX: {
     // Perform the following transformation.

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 799c1f5..d89a1d5 100644 (file)
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -3219,3 +3219,24 @@ void X86FrameLowering::processFunctionBeforeFrameFinalized(
                     UnwindHelpFI)
       .addImm(-2);
 }
+
+void X86FrameLowering::processFunctionBeforeFrameIndicesReplaced(
+    MachineFunction &MF, RegScavenger *RS) const {
+  if (STI.is32Bit() && MF.hasEHFunclets())
+    restoreWinEHStackPointersInParent(MF);
+}
+
+void X86FrameLowering::restoreWinEHStackPointersInParent(
+    MachineFunction &MF) const {
+  // 32-bit functions have to restore stack pointers when control is transferred
+  // back to the parent function. These blocks are identified as eh pads that
+  // are not funclet entries.
+  bool IsSEH = isAsynchronousEHPersonality(
+      classifyEHPersonality(MF.getFunction().getPersonalityFn()));
+  for (MachineBasicBlock &MBB : MF) {
+    bool NeedsRestore = MBB.isEHPad() && !MBB.isEHFuncletEntry();
+    if (NeedsRestore)
+      restoreWin32EHStackPointers(MBB, MBB.begin(), DebugLoc(),
+                                  /*RestoreSP=*/IsSEH);
+  }
+}

diff --git a/llvm/lib/Target/X86/X86FrameLowering.h b/llvm/lib/Target/X86/X86FrameLowering.h
index 2103d64..24f4a03 100644 (file)
--- a/llvm/lib/Target/X86/X86FrameLowering.h
+++ b/llvm/lib/Target/X86/X86FrameLowering.h
@@ -116,6 +116,10 @@ public:
   void processFunctionBeforeFrameFinalized(MachineFunction &MF,
                                            RegScavenger *RS) const override;
 
+  void
+  processFunctionBeforeFrameIndicesReplaced(MachineFunction &MF,
+                                            RegScavenger *RS) const override;
+
   /// Check the instruction before/after the passed instruction. If
   /// it is an ADD/SUB/LEA instruction it is deleted argument and the
   /// stack adjustment is returned as a positive value for ADD/LEA and
@@ -169,6 +173,8 @@ public:
                               MachineBasicBlock::iterator MBBI,
                               const DebugLoc &DL, bool RestoreSP = false) const;
 
+  void restoreWinEHStackPointersInParent(MachineFunction &MF) const;
+
   int getInitialCFAOffset(const MachineFunction &MF) const override;
 
   unsigned getInitialCFARegister(const MachineFunction &MF) const override;

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 58d797c..81b4b48 100644 (file)
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -31273,29 +31273,16 @@ X86TargetLowering::EmitLoweredCatchRet(MachineInstr &MI,
   BB->addSuccessor(RestoreMBB);
   MI.getOperand(0).setMBB(RestoreMBB);
 
+  // Marking this as an EH pad but not a funclet entry block causes PEI to
+  // restore stack pointers in the block.
+  RestoreMBB->setIsEHPad(true);
+
   auto RestoreMBBI = RestoreMBB->begin();
-  BuildMI(*RestoreMBB, RestoreMBBI, DL, TII.get(X86::EH_RESTORE));
   BuildMI(*RestoreMBB, RestoreMBBI, DL, TII.get(X86::JMP_4)).addMBB(TargetMBB);
   return BB;
 }
 
 MachineBasicBlock *
-X86TargetLowering::EmitLoweredCatchPad(MachineInstr &MI,
-                                       MachineBasicBlock *BB) const {
-  MachineFunction *MF = BB->getParent();
-  const Constant *PerFn = MF->getFunction().getPersonalityFn();
-  bool IsSEH = isAsynchronousEHPersonality(classifyEHPersonality(PerFn));
-  // Only 32-bit SEH requires special handling for catchpad.
-  if (IsSEH && Subtarget.is32Bit()) {
-    const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
-    DebugLoc DL = MI.getDebugLoc();
-    BuildMI(*BB, MI, DL, TII.get(X86::EH_RESTORE));
-  }
-  MI.eraseFromParent();
-  return BB;
-}
-
-MachineBasicBlock *
 X86TargetLowering::EmitLoweredTLSAddr(MachineInstr &MI,
                                       MachineBasicBlock *BB) const {
   // So, here we replace TLSADDR with the sequence:
@@ -32283,8 +32270,6 @@ X86TargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
     return EmitLoweredRetpoline(MI, BB);
   case X86::CATCHRET:
     return EmitLoweredCatchRet(MI, BB);
-  case X86::CATCHPAD:
-    return EmitLoweredCatchPad(MI, BB);
   case X86::SEG_ALLOCA_32:
   case X86::SEG_ALLOCA_64:
     return EmitLoweredSegAlloca(MI, BB);

diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index c14ccc9..6f3aad8 100644 (file)
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -1462,9 +1462,6 @@ namespace llvm {
     MachineBasicBlock *EmitLoweredCatchRet(MachineInstr &MI,
                                            MachineBasicBlock *BB) const;
 
-    MachineBasicBlock *EmitLoweredCatchPad(MachineInstr &MI,
-                                           MachineBasicBlock *BB) const;
-
     MachineBasicBlock *EmitLoweredSegAlloca(MachineInstr &MI,
                                             MachineBasicBlock *BB) const;
 

diff --git a/llvm/lib/Target/X86/X86InstrCompiler.td b/llvm/lib/Target/X86/X86InstrCompiler.td
index 841453e..539c073 100644 (file)
--- a/llvm/lib/Target/X86/X86InstrCompiler.td
+++ b/llvm/lib/Target/X86/X86InstrCompiler.td
@@ -177,18 +177,6 @@ let isTerminator = 1, hasSideEffects = 1, isBarrier = 1, hasCtrlDep = 1,
                      [(catchret bb:$dst, bb:$from)]>;
 }
 
-let hasSideEffects = 1, hasCtrlDep = 1, isCodeGenOnly = 1,
-    usesCustomInserter = 1 in
-def CATCHPAD : I<0, Pseudo, (outs), (ins), "# CATCHPAD", [(catchpad)]>;
-
-// This instruction is responsible for re-establishing stack pointers after an
-// exception has been caught and we are rejoining normal control flow in the
-// parent function or funclet. It generally sets ESP and EBP, and optionally
-// ESI. It is only needed for 32-bit WinEH, as the runtime restores CSRs for us
-// elsewhere.
-let hasSideEffects = 1, hasCtrlDep = 1, isCodeGenOnly = 1 in
-def EH_RESTORE : I<0, Pseudo, (outs), (ins), "# EH_RESTORE", []>;
-
 let hasSideEffects = 1, isBarrier = 1, isCodeGenOnly = 1,
     usesCustomInserter = 1 in {
   def EH_SjLj_SetJmp32  : I<0, Pseudo, (outs GR32:$dst), (ins i32mem:$buf),

diff --git a/llvm/test/CodeGen/X86/seh-except-restore.ll b/llvm/test/CodeGen/X86/seh-except-restore.ll
new file mode 100644 (file)
index 0000000..4e9d702
--- /dev/null
+++ b/llvm/test/CodeGen/X86/seh-except-restore.ll
@@ -0,0 +1,69 @@
+; RUN: llc < %s | FileCheck %s
+
+; In PR44697, the register allocator inserted loads into the __except block
+; before the instructions that restore EBP and ESP back to what they should be.
+; Make sure they are the first instructions in the __except block.
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:x-p:32:32-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc19.24.28315"
+
+declare i8* @llvm.frameaddress.p0i8(i32 immarg)
+declare i8* @llvm.eh.recoverfp(i8*, i8*)
+declare i8* @llvm.localrecover(i8*, i8*, i32 immarg)
+declare dso_local i32 @_except_handler3(...)
+declare void @llvm.localescape(...)
+
+define dso_local zeroext i1 @invokewrapper(
+    void ()* nocapture %Fn,
+    i1 zeroext %DumpStackAndCleanup,
+    i32* nocapture dereferenceable(4) %RetCode)
+        personality i32 (...)* @_except_handler3 {
+entry:
+  %__exception_code = alloca i32, align 4
+  call void (...) @llvm.localescape(i32* nonnull %__exception_code)
+  invoke void %Fn()
+          to label %return unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %0 = catchswitch within none [label %__except.ret] unwind to caller
+
+__except.ret:                                     ; preds = %catch.dispatch
+  %1 = catchpad within %0 [i8* bitcast (i32 ()* @filter to i8*)]
+  catchret from %1 to label %__except
+
+__except:                                         ; preds = %__except.ret
+  %2 = load i32, i32* %__exception_code, align 4
+  store i32 %2, i32* %RetCode, align 4
+  br label %return
+
+return:                                           ; preds = %entry, %__except
+  %retval.0 = phi i1 [ false, %__except ], [ true, %entry ]
+  ret i1 %retval.0
+}
+
+; CHECK-LABEL: _invokewrapper:                         # @invokewrapper
+; CHECK:         calll   *8(%ebp)
+; CHECK: LBB0_2:                                 # %return
+
+; CHECK: LBB0_1:                                 # %__except.ret
+; CHECK-NEXT:         movl    -24(%ebp), %esp
+; CHECK-NEXT:         addl    $12, %ebp
+
+; Function Attrs: nofree nounwind
+define internal i32 @filter() {
+entry:
+  %0 = tail call i8* @llvm.frameaddress.p0i8(i32 1)
+  %1 = tail call i8* @llvm.eh.recoverfp(i8* bitcast (i1 (void ()*, i1, i32*)* @invokewrapper to i8*), i8* %0)
+  %2 = tail call i8* @llvm.localrecover(i8* bitcast (i1 (void ()*, i1, i32*)* @invokewrapper to i8*), i8* %1, i32 0)
+  %__exception_code = bitcast i8* %2 to i32*
+  %3 = getelementptr inbounds i8, i8* %0, i32 -20
+  %4 = bitcast i8* %3 to { i32*, i8* }**
+  %5 = load { i32*, i8* }*, { i32*, i8* }** %4, align 4
+  %6 = getelementptr inbounds { i32*, i8* }, { i32*, i8* }* %5, i32 0, i32 0
+  %7 = load i32*, i32** %6, align 4
+  %8 = load i32, i32* %7, align 4
+  store i32 %8, i32* %__exception_code, align 4
+  ret i32 1
+}