Backport fixes for aarch64-pc-windows-msvc (#46)

* [AArch64] Fix mismatch in prologue and epilogue for funclets on Windows

The generated code for a funclet can have an add to sp in the epilogue
for which there is no corresponding sub in the prologue.

This patch removes the early return from emitPrologue that was
preventing the sub to sp, and instead conditionalizes the appropriate
parts of the rest of the function.

Fixes https://bugs.llvm.org/show_bug.cgi?id=45345

Differential Revision: https://reviews.llvm.org/D77015

* [AArch64] Change AArch64 Windows EH UnwindHelp object to be a fixed object

The UnwindHelp object is used during exception handling by runtime
code. It must be findable from a fixed offset from FP.

This change allocates the UnwindHelp object as a fixed object (as is
done for x86_64) to ensure that both the generated code and runtime
agree on the location of the object.

Fixes https://bugs.llvm.org/show_bug.cgi?id=45346

Differential Revision: https://reviews.llvm.org/D77016

Author: danielframpton

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -211,6 +211,24 @@ AArch64FrameLowering::getStackIDForScalableVectors() const {
   return TargetStackID::SVEVector;
 }
 
+/// Returns the size of the fixed object area (allocated next to sp on entry)
+/// On Win64 this may include a var args area and an UnwindHelp object for EH.
+static unsigned getFixedObjectSize(const MachineFunction &MF,
+                                   const AArch64FunctionInfo *AFI, bool IsWin64,
+                                   bool IsFunclet) {
+  if (!IsWin64 || IsFunclet) {
+    // Only Win64 uses fixed objects, and then only for the function (not
+    // funclets)
+    return 0;
+  } else {
+    // Var args are stored here in the primary function.
+    const unsigned VarArgsArea = AFI->getVarArgsGPRSize();
+    // To support EH funclets we allocate an UnwindHelp object
+    const unsigned UnwindHelpObject = (MF.hasEHFunclets() ? 8 : 0);
+    return alignTo(VarArgsArea + UnwindHelpObject, 16);
+  }
+}
+
 /// Returns the size of the entire SVE stackframe (calleesaves + spills).
 static StackOffset getSVEStackSize(const MachineFunction &MF) {
   const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
@@ -959,10 +977,7 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
 
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
-  // Var args are accounted for in the containing function, so don't
-  // include them for funclets.
-  unsigned FixedObject = (IsWin64 && !IsFunclet) ?
-                         alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
+  unsigned FixedObject = getFixedObjectSize(MF, AFI, IsWin64, IsFunclet);
 
   auto PrologueSaveSize = AFI->getCalleeSavedStackSize() + FixedObject;
   // All of the remaining stack allocations are for locals.
@@ -993,32 +1008,8 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
     ++MBBI;
   }
 
-  // The code below is not applicable to funclets. We have emitted all the SEH
-  // opcodes that we needed to emit.  The FP and BP belong to the containing
-  // function.
-  if (IsFunclet) {
-    if (NeedsWinCFI) {
-      HasWinCFI = true;
-      BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_PrologEnd))
-          .setMIFlag(MachineInstr::FrameSetup);
-    }
-
-    // SEH funclets are passed the frame pointer in X1.  If the parent
-    // function uses the base register, then the base register is used
-    // directly, and is not retrieved from X1.
-    if (F.hasPersonalityFn()) {
-      EHPersonality Per = classifyEHPersonality(F.getPersonalityFn());
-      if (isAsynchronousEHPersonality(Per)) {
-        BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::COPY), AArch64::FP)
-            .addReg(AArch64::X1).setMIFlag(MachineInstr::FrameSetup);
-        MBB.addLiveIn(AArch64::X1);
-      }
-    }
-
-    return;
-  }
-
-  if (HasFP) {
+  // For funclets the FP belongs to the containing function.
+  if (!IsFunclet && HasFP) {
     // Only set up FP if we actually need to.
     int64_t FPOffset = isTargetDarwin(MF) ? (AFI->getCalleeSavedStackSize() - 16) : 0;
 
@@ -1161,7 +1152,9 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
 
   // Allocate space for the rest of the frame.
   if (NumBytes) {
-    const bool NeedsRealignment = RegInfo->needsStackRealignment(MF);
+    // Alignment is required for the parent frame, not the funclet
+    const bool NeedsRealignment =
+        !IsFunclet && RegInfo->needsStackRealignment(MF);
     unsigned scratchSPReg = AArch64::SP;
 
     if (NeedsRealignment) {
@@ -1215,7 +1208,8 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
   // FIXME: Clarify FrameSetup flags here.
   // Note: Use emitFrameOffset() like above for FP if the FrameSetup flag is
   // needed.
-  if (RegInfo->hasBasePointer(MF)) {
+  // For funclets the BP belongs to the containing function.
+  if (!IsFunclet && RegInfo->hasBasePointer(MF)) {
     TII->copyPhysReg(MBB, MBBI, DL, RegInfo->getBaseRegister(), AArch64::SP,
                      false);
     if (NeedsWinCFI) {
@@ -1232,6 +1226,19 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
         .setMIFlag(MachineInstr::FrameSetup);
   }
 
+  // SEH funclets are passed the frame pointer in X1.  If the parent
+  // function uses the base register, then the base register is used
+  // directly, and is not retrieved from X1.
+  if (IsFunclet && F.hasPersonalityFn()) {
+    EHPersonality Per = classifyEHPersonality(F.getPersonalityFn());
+    if (isAsynchronousEHPersonality(Per)) {
+      BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::COPY), AArch64::FP)
+          .addReg(AArch64::X1)
+          .setMIFlag(MachineInstr::FrameSetup);
+      MBB.addLiveIn(AArch64::X1);
+    }
+  }
+
   if (needsFrameMoves) {
     const DataLayout &TD = MF.getDataLayout();
     const int StackGrowth = isTargetDarwin(MF)
@@ -1450,10 +1457,7 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
 
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
-  // Var args are accounted for in the containing function, so don't
-  // include them for funclets.
-  unsigned FixedObject =
-      (IsWin64 && !IsFunclet) ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
+  unsigned FixedObject = getFixedObjectSize(MF, AFI, IsWin64, IsFunclet);
 
   uint64_t AfterCSRPopSize = ArgumentPopSize;
   auto PrologueSaveSize = AFI->getCalleeSavedStackSize() + FixedObject;
@@ -1679,7 +1683,9 @@ static StackOffset getFPOffset(const MachineFunction &MF, int64_t ObjectOffset)
   const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
-  unsigned FixedObject = IsWin64 ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
+
+  unsigned FixedObject =
+      getFixedObjectSize(MF, AFI, IsWin64, /*IsFunclet=*/false);
   unsigned FPAdjust = isTargetDarwin(MF)
                         ? 16 : AFI->getCalleeSavedStackSize(MF.getFrameInfo());
   return {ObjectOffset + FixedObject + FPAdjust, MVT::i8};
@@ -2632,9 +2638,14 @@ void AArch64FrameLowering::processFunctionBeforeFrameFinalized(
     ++MBBI;
 
   // Create an UnwindHelp object.
-  int UnwindHelpFI =
-      MFI.CreateStackObject(/*size*/8, /*alignment*/16, false);
+  // The UnwindHelp object is allocated at the start of the fixed object area
+  int64_t FixedObject =
+      getFixedObjectSize(MF, AFI, /*IsWin64*/ true, /*IsFunclet*/ false);
+  int UnwindHelpFI = MFI.CreateFixedObject(/*Size*/ 8,
+                                           /*SPOffset*/ -FixedObject,
+                                           /*IsImmutable=*/false);
   EHInfo.UnwindHelpFrameIdx = UnwindHelpFI;
+
   // We need to store -2 into the UnwindHelp object at the start of the
   // function.
   DebugLoc DL;
@@ -2656,10 +2667,14 @@ int AArch64FrameLowering::getFrameIndexReferencePreferSP(
     const MachineFunction &MF, int FI, unsigned &FrameReg,
     bool IgnoreSPUpdates) const {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
-  LLVM_DEBUG(dbgs() << "Offset from the SP for " << FI << " is "
-                    << MFI.getObjectOffset(FI) << "\n");
-  FrameReg = AArch64::SP;
-  return MFI.getObjectOffset(FI);
+  if (IgnoreSPUpdates) {
+    LLVM_DEBUG(dbgs() << "Offset from the SP for " << FI << " is "
+                      << MFI.getObjectOffset(FI) << "\n");
+    FrameReg = AArch64::SP;
+    return MFI.getObjectOffset(FI);
+  }
+
+  return getFrameIndexReference(MF, FI, FrameReg);
 }
 
 /// The parent frame offset (aka dispFrame) is only used on X86_64 to retrieve

llvm/test/CodeGen/AArch64/funclet-match-add-sub-stack.ll

@@ -0,0 +1,62 @@
+; RUN: llc -o - %s -mtriple=aarch64-windows | FileCheck %s
+; Check that the stack bump around a funclet is computed correctly in both the
+; prologue and epilogue in the case we have a MaxCallFrameSize > 0 and are doing alloca
+target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-pc-windows-msvc19.25.28611"
+
+; // requires passing arguments on the stack
+; void test2(void*, int, int, int, int, int, int, int, int);
+;
+; // function with the funclet being checked
+; void test1(size_t bytes)
+; {
+;   // alloca forces a separate callee save bump and stack bump
+;   void *data = _alloca(bytes);
+;   try {
+;     test2(data, 0, 1, 2, 3, 4, 5, 6, 7);
+;   } catch (...) {
+;     // the funclet being checked
+;   }
+; }
+
+; CHECK-LABEL: ?catch$2@?0??test1@@YAX_K@Z@4HA
+; CHECK: sub sp, sp, #16
+; CHECK: add sp, sp, #16
+; Function Attrs: uwtable
+define dso_local void @"?test1@@YAX_K@Z"(i64 %0) #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+  %2 = alloca i64, align 8
+  %3 = alloca i8*, align 8
+  store i64 %0, i64* %2, align 8
+  %4 = load i64, i64* %2, align 8
+  %5 = alloca i8, i64 %4, align 16
+  store i8* %5, i8** %3, align 8
+  %6 = load i8*, i8** %3, align 8
+  invoke void @"?test2@@YAXPEAXHHHHHHHH@Z"(i8* %6, i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7)
+          to label %13 unwind label %7
+
+7:                                                ; preds = %1
+  %8 = catchswitch within none [label %9] unwind to caller
+
+9:                                                ; preds = %7
+  %10 = catchpad within %8 [i8* null, i32 64, i8* null]
+  catchret from %10 to label %11
+
+11:                                               ; preds = %9
+  br label %12
+
+12:                                               ; preds = %11, %13
+  ret void
+
+13:                                               ; preds = %1
+  br label %12
+}
+
+declare dso_local void @"?test2@@YAXPEAXHHHHHHHH@Z"(i8*, i32, i32, i32, i32, i32, i32, i32, i32) #1
+
+declare dso_local i32 @__CxxFrameHandler3(...)
+
+attributes #0 = { uwtable }
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"wchar_size", i32 2}

llvm/test/CodeGen/AArch64/seh-finally.ll

@@ -37,7 +37,7 @@ entry:
 ; CHECK-LABEL: simple_seh
 ; CHECK: add     x29, sp, #16
 ; CHECK: mov     x0, #-2
-; CHECK: stur    x0, [x29, #-16]
+; CHECK: stur    x0, [x29, #16]
 ; CHECK: .set .Lsimple_seh$frame_escape_0, -8
 ; CHECK: ldur    w0, [x29, #-8]
 ; CHECK: bl      foo
@@ -87,13 +87,13 @@ define void @stack_realign() #0 personality i8* bitcast (i32 (...)* @__C_specifi
 entry:
 ; CHECK-LABEL: stack_realign
 ; CHECK: mov     x29, sp
-; CHECK: sub     x9, sp, #64
+; CHECK: sub     x9, sp, #16
 ; CHECK: and     sp, x9, #0xffffffffffffffe0
 ; CHECK: mov     x19, sp
 ; CHECK: mov     x0, #-2
-; CHECK: stur    x0, [x19, #16]
-; CHECK: .set .Lstack_realign$frame_escape_0, 32
-; CHECK: ldr     w0, [x19, #32]
+; CHECK: stur    x0, [x29, #32]
+; CHECK: .set .Lstack_realign$frame_escape_0, 0
+; CHECK: ldr     w0, [x19]
 ; CHECK: bl      foo
 
   %o = alloca %struct.S, align 32
@@ -142,7 +142,7 @@ entry:
 ; CHECK-LABEL: vla_present
 ; CHECK: add     x29, sp, #32
 ; CHECK: mov     x1, #-2
-; CHECK: stur    x1, [x29, #-32]
+; CHECK: stur    x1, [x29, #16]
 ; CHECK: .set .Lvla_present$frame_escape_0, -4
 ; CHECK: stur    w0, [x29, #-4]
 ; CHECK: ldur    w8, [x29, #-4]
@@ -206,17 +206,17 @@ define void @vla_and_realign(i32 %n) #0 personality i8* bitcast (i32 (...)* @__C
 entry:
 ; CHECK-LABEL: vla_and_realign
 ; CHECK: mov     x29, sp
-; CHECK: sub     x9, sp, #64
+; CHECK: sub     x9, sp, #48
 ; CHECK: and     sp, x9, #0xffffffffffffffe0
 ; CHECK: mov     x19, sp
 ; CHECK: mov     x1, #-2
-; CHECK: stur    x1, [x19]
+; CHECK: stur    x1, [x29, #32]
 ; CHECK: .set .Lvla_and_realign$frame_escape_0, 32
-; CHECK: str     w0, [x29, #28]
-; CHECK: ldr     w8, [x29, #28]
+; CHECK: str     w0, [x29, #44]
+; CHECK: ldr     w8, [x29, #44]
 ; CHECK: mov     x9, sp
-; CHECK: str     x9, [x19, #24]
-; CHECK: str     x8, [x19, #16]
+; CHECK: str     x9, [x29, #24]
+; CHECK: str     x8, [x19, #24]
 ; CHECK: ldr     w0, [x19, #32]
 ; CHECK: bl      foo
 

llvm/test/CodeGen/AArch64/wineh-try-catch-cbz.ll

@@ -4,11 +4,10 @@
 ; but the original issue only reproduced if the cbz was immediately
 ; after the frame setup.)
 
-; CHECK:      sub     sp, sp, #32
-; CHECK-NEXT: stp     x29, x30, [sp, #16]
-; CHECK-NEXT: add     x29, sp, #16
+; CHECK: stp     x29, x30, [sp, #-32]!
+; CHECK-NEXT: mov     x29, sp
 ; CHECK-NEXT: mov     x1, #-2
-; CHECK-NEXT: stur    x1, [x29, #-16]
+; CHECK-NEXT: stur    x1, [x29, #16]
 ; CHECK-NEXT: cbz     w0, .LBB0_2
 
 target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"

llvm/test/CodeGen/AArch64/wineh-try-catch-realign.ll

@@ -12,7 +12,7 @@
 ; CHECK:      stp     x29, x30, [sp, #-32]!
 ; CHECK-NEXT: str     x28, [sp, #16]
 ; CHECK-NEXT: str     x19, [sp, #24]
-; CHECK-NEXT: add     x0, x19, #64
+; CHECK-NEXT: add     x0, x19, #0
 ; CHECK-NEXT: mov     w1, wzr
 ; CHECK-NEXT: bl      "?bb@@YAXPEAHH@Z"
 ; CHECK-NEXT: adrp    x0, .LBB0_1

llvm/test/CodeGen/AArch64/wineh-try-catch.ll

@@ -11,19 +11,19 @@
 ;    and the parent function.
 
 ; The following checks that the unwind help object has -2 stored into it at
-; fp - 400 - 256 = fp - 656, which is on-entry sp - 48 + 32 - 656 =
-; on-entry sp - 672.  We check this offset in the table later on.
+; fp + 16, which is on-entry sp - 16.
+; We check this offset in the table later on.
 
 ; CHECK-LABEL: "?func@@YAHXZ":
-; CHECK:       stp     x29, x30, [sp, #-48]!
+; CHECK:       stp     x29, x30, [sp, #-64]!
 ; CHECK:       str     x28, [sp, #16]
 ; CHECK:       str     x21, [sp, #24]
 ; CHECK:       stp     x19, x20, [sp, #32]
 ; CHECK:       mov     x29, sp
 ; CHECK:       sub     sp, sp, #624
 ; CHECK:       mov     x19, sp
 ; CHECK:       mov     x0, #-2
-; CHECK:       stur    x0, [x19]
+; CHECK:       stur    x0, [x29, #48]
 
 ; Now check that x is stored at fp - 20.  We check that this is the same
 ; location accessed from the funclet to retrieve x.
@@ -72,7 +72,7 @@
 
 ; Now check that the offset of the unwind help object from the stack pointer on
 ; entry to func is encoded in cppxdata that is passed to __CxxFrameHandler3.  As
-; computed above, this comes to -672.
+; computed above, this comes to -16.
 ; CHECK-LABEL:        "$cppxdata$?func@@YAHXZ":
 ; CHECK-NEXT:         .word   429065506               ; MagicNumber
 ; CHECK-NEXT:         .word   2                       ; MaxState
@@ -81,7 +81,7 @@
 ; CHECK-NEXT:         .word   ("$tryMap$?func@@YAHXZ")@IMGREL ; TryBlockMap
 ; CHECK-NEXT:         .word   4                       ; IPMapEntries
 ; CHECK-NEXT:         .word   ("$ip2state$?func@@YAHXZ")@IMGREL ; IPToStateXData
-; CHECK-NEXT:         .word   -672                    ; UnwindHelp
+; CHECK-NEXT:         .word   -16                     ; UnwindHelp
 
 ; UNWIND: Function: ?func@@YAHXZ (0x0)
 ; UNWIND: Prologue [
@@ -91,7 +91,7 @@
 ; UNWIND-NEXT: ; stp x19, x20, [sp, #32]
 ; UNWIND-NEXT: ; str x21, [sp, #24]
 ; UNWIND-NEXT: ; str x28, [sp, #16]
-; UNWIND-NEXT: ; stp x29, x30, [sp, #-48]!
+; UNWIND-NEXT: ; stp x29, x30, [sp, #-64]!
 ; UNWIND-NEXT: ; end
 ; UNWIND: Function: ?catch$2@?0??func@@YAHXZ@4HA
 ; UNWIND: Prologue [

llvm/test/CodeGen/AArch64/wineh-unwindhelp-via-fp.ll

@@ -0,0 +1,69 @@
+; RUN: llc -o - %s -mtriple=aarch64-windows | FileCheck %s
+; Check that we allocate the unwind help stack object in a fixed location from fp
+; so that the runtime can find it when handling an exception
+target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-pc-windows-msvc19.25.28611"
+
+; Check that the store to the unwind help object for func2 is via FP
+; CHECK-LABEL: ?func2@@YAXXZ
+; CHECK: mov x[[#SCRATCH_REG:]], #-2
+; CHECK: stur x[[#SCRATCH_REG:]], [x29, #[[#]]]
+;
+; // struct that requires greater than stack alignment
+; struct alignas(32) A
+; {
+;     // data that would be invalid for unwind help (> 0)
+;     int _x[4]{42, 42, 42, 42};
+;     ~A() {}
+; };
+; 
+; // cause us to run the funclet in func2
+; void func3()
+; {
+;     throw 1;
+; }
+; 
+; // the funclet that ensures we have the unwind help correct
+; void func2()
+; {
+;     A a;
+;     func3();
+; }
+; 
+; // function to ensure we are misaligned in func2
+; void func1()
+; {
+;     func2();
+; }
+; 
+; // set things up and ensure alignment for func1
+; void test()
+; {
+;     try {
+;         A a;
+;         func1();
+;     } catch(...) {}
+; }
+
+%struct.A = type { [4 x i32], [16 x i8] }
+declare dso_local %struct.A* @"??0A@@QEAA@XZ"(%struct.A* returned %0)
+declare dso_local void @"??1A@@QEAA@XZ"(%struct.A* %0)
+declare dso_local i32 @__CxxFrameHandler3(...)
+declare dso_local void @"?func3@@YAXXZ"()
+
+; Function Attrs: noinline optnone uwtable
+define dso_local void @"?func2@@YAXXZ"() #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+  %1 = alloca %struct.A, align 32
+  %2 = call %struct.A* @"??0A@@QEAA@XZ"(%struct.A* %1) #3
+  invoke void @"?func3@@YAXXZ"()
+          to label %3 unwind label %4
+
+3:                                                ; preds = %0
+  call void @"??1A@@QEAA@XZ"(%struct.A* %1) #3
+  ret void
+
+4:                                                ; preds = %0
+  %5 = cleanuppad within none []
+  call void @"??1A@@QEAA@XZ"(%struct.A* %1) #3 [ "funclet"(token %5) ]
+  cleanupret from %5 unwind to caller
+}