[AArch64][Darwin][SME] Don't try to save VG to the stack for unwinding.

On Darwin we don't have any hardware that has SVE support, only SME.
Therefore we don't need to save VG for unwinders and can safely omit it.

This also fixes crashes introduced since this feature landed since Darwin's
compact unwind code can't handle the presence of VG anyway.

rdar://131072344

Author: aemerson

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -1394,6 +1394,18 @@ bool requiresGetVGCall(MachineFunction &MF) {
          !MF.getSubtarget<AArch64Subtarget>().hasSVE();
 }
 
+static bool requiresSaveVG(MachineFunction &MF) {
+  AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
+  // For Darwin platforms we don't save VG for non-SVE functions, even if SME
+  // is enabled with streaming mode changes.
+  if (!AFI->hasStreamingModeChanges())
+    return false;
+  auto &ST = MF.getSubtarget<AArch64Subtarget>();
+  if (ST.isTargetDarwin())
+    return ST.hasSVE();
+  return true;
+}
+
 bool isVGInstruction(MachineBasicBlock::iterator MBBI) {
   unsigned Opc = MBBI->getOpcode();
   if (Opc == AArch64::CNTD_XPiI || Opc == AArch64::RDSVLI_XI ||
@@ -1430,8 +1442,7 @@ static MachineBasicBlock::iterator convertCalleeSaveRestoreToSPPrePostIncDec(
   // functions, we need to do this for both the streaming and non-streaming
   // vector length. Move past these instructions if necessary.
   MachineFunction &MF = *MBB.getParent();
-  AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
-  if (AFI->hasStreamingModeChanges())
+  if (requiresSaveVG(MF))
     while (isVGInstruction(MBBI))
       ++MBBI;
 
@@ -1937,7 +1948,7 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
   while (MBBI != End && MBBI->getFlag(MachineInstr::FrameSetup) &&
          !IsSVECalleeSave(MBBI)) {
     // Move past instructions generated to calculate VG
-    if (AFI->hasStreamingModeChanges())
+    if (requiresSaveVG(MF))
       while (isVGInstruction(MBBI))
         ++MBBI;
 
@@ -3720,7 +3731,7 @@ void AArch64FrameLowering::determineCalleeSaves(MachineFunction &MF,
   // non-streaming VG value.
   const Function &F = MF.getFunction();
   SMEAttrs Attrs(F);
-  if (AFI->hasStreamingModeChanges()) {
+  if (requiresSaveVG(MF)) {
     if (Attrs.hasStreamingBody() && !Attrs.hasStreamingInterface())
       CSStackSize += 16;
     else
@@ -3873,7 +3884,7 @@ bool AArch64FrameLowering::assignCalleeSavedSpillSlots(
   }
 
   // Insert VG into the list of CSRs, immediately before LR if saved.
-  if (AFI->hasStreamingModeChanges()) {
+  if (requiresSaveVG(MF)) {
     std::vector<CalleeSavedInfo> VGSaves;
     SMEAttrs Attrs(MF.getFunction());
 
@@ -4602,10 +4613,9 @@ MachineBasicBlock::iterator emitVGSaveRestore(MachineBasicBlock::iterator II,
 
 void AArch64FrameLowering::processFunctionBeforeFrameIndicesReplaced(
     MachineFunction &MF, RegScavenger *RS = nullptr) const {
-  AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
   for (auto &BB : MF)
     for (MachineBasicBlock::iterator II = BB.begin(); II != BB.end();) {
-      if (AFI->hasStreamingModeChanges())
+      if (requiresSaveVG(MF))
         II = emitVGSaveRestore(II, this);
       if (StackTaggingMergeSetTag)
         II = tryMergeAdjacentSTG(II, this, RS);

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -8732,10 +8732,11 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
 
   SDValue InGlue;
   if (RequiresSMChange) {
-
-    Chain = DAG.getNode(AArch64ISD::VG_SAVE, DL,
-                        DAG.getVTList(MVT::Other, MVT::Glue), Chain);
-    InGlue = Chain.getValue(1);
+    if (!Subtarget->isTargetDarwin() || Subtarget->hasSVE()) {
+      Chain = DAG.getNode(AArch64ISD::VG_SAVE, DL,
+                          DAG.getVTList(MVT::Other, MVT::Glue), Chain);
+      InGlue = Chain.getValue(1);
+    }
 
     SDValue NewChain = changeStreamingMode(
         DAG, DL, CalleeAttrs.hasStreamingInterface(), Chain, InGlue,
@@ -8914,11 +8915,13 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
     Result = changeStreamingMode(
         DAG, DL, !CalleeAttrs.hasStreamingInterface(), Result, InGlue,
         getSMCondition(CallerAttrs, CalleeAttrs), PStateSM);
-    InGlue = Result.getValue(1);
 
-    Result =
-        DAG.getNode(AArch64ISD::VG_RESTORE, DL,
-                    DAG.getVTList(MVT::Other, MVT::Glue), {Result, InGlue});
+    if (!Subtarget->isTargetDarwin() || Subtarget->hasSVE()) {
+      InGlue = Result.getValue(1);
+      Result =
+          DAG.getNode(AArch64ISD::VG_RESTORE, DL,
+                      DAG.getVTList(MVT::Other, MVT::Glue), {Result, InGlue});
+    }
   }
 
   if (CallerAttrs.requiresEnablingZAAfterCall(CalleeAttrs))

llvm/test/CodeGen/AArch64/sme-darwin-no-sve-vg.ll

@@ -0,0 +1,161 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -o - %s | FileCheck %s
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "arm64-apple-macosx14.0.0"
+
+; Check we don't crash on Darwin and that we don't try to save VG
+; when only SME (and not SVE) is enabled.
+
+; Function Attrs: mustprogress norecurse nounwind ssp uwtable(sync)
+define noundef i32 @main() local_unnamed_addr #0 {
+; CHECK-LABEL: main:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    stp d15, d14, [sp, #-80]! ; 16-byte Folded Spill
+; CHECK-NEXT:    .cfi_def_cfa_offset 80
+; CHECK-NEXT:    stp d13, d12, [sp, #16] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp d11, d10, [sp, #32] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp d9, d8, [sp, #48] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp x29, x30, [sp, #64] ; 16-byte Folded Spill
+; CHECK-NEXT:    .cfi_offset w30, -8
+; CHECK-NEXT:    .cfi_offset w29, -16
+; CHECK-NEXT:    .cfi_offset b8, -24
+; CHECK-NEXT:    .cfi_offset b9, -32
+; CHECK-NEXT:    .cfi_offset b10, -40
+; CHECK-NEXT:    .cfi_offset b11, -48
+; CHECK-NEXT:    .cfi_offset b12, -56
+; CHECK-NEXT:    .cfi_offset b13, -64
+; CHECK-NEXT:    .cfi_offset b14, -72
+; CHECK-NEXT:    .cfi_offset b15, -80
+; CHECK-NEXT:    smstart sm
+; CHECK-NEXT:    bl __ZL9sme_crashv
+; CHECK-NEXT:    smstop sm
+; CHECK-NEXT:    mov w0, #0 ; =0x0
+; CHECK-NEXT:    ldp x29, x30, [sp, #64] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d9, d8, [sp, #48] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d11, d10, [sp, #32] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d13, d12, [sp, #16] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d15, d14, [sp], #80 ; 16-byte Folded Reload
+; CHECK-NEXT:    .cfi_def_cfa_offset 0
+; CHECK-NEXT:    .cfi_restore w30
+; CHECK-NEXT:    .cfi_restore w29
+; CHECK-NEXT:    .cfi_restore b8
+; CHECK-NEXT:    .cfi_restore b9
+; CHECK-NEXT:    .cfi_restore b10
+; CHECK-NEXT:    .cfi_restore b11
+; CHECK-NEXT:    .cfi_restore b12
+; CHECK-NEXT:    .cfi_restore b13
+; CHECK-NEXT:    .cfi_restore b14
+; CHECK-NEXT:    .cfi_restore b15
+; CHECK-NEXT:    ret
+entry:
+  tail call fastcc void @_ZL9sme_crashv() #4
+  ret i32 0
+}
+
+; Function Attrs: mustprogress norecurse nounwind ssp uwtable(sync)
+define internal fastcc void @_ZL9sme_crashv() unnamed_addr #1 {
+; CHECK-LABEL: _ZL9sme_crashv:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    stp d15, d14, [sp, #-96]! ; 16-byte Folded Spill
+; CHECK-NEXT:    .cfi_def_cfa_offset 96
+; CHECK-NEXT:    stp d13, d12, [sp, #16] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp d11, d10, [sp, #32] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp d9, d8, [sp, #48] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp x28, x27, [sp, #64] ; 16-byte Folded Spill
+; CHECK-NEXT:    stp x29, x30, [sp, #80] ; 16-byte Folded Spill
+; CHECK-NEXT:    add x29, sp, #80
+; CHECK-NEXT:    .cfi_def_cfa w29, 16
+; CHECK-NEXT:    .cfi_offset w30, -8
+; CHECK-NEXT:    .cfi_offset w29, -16
+; CHECK-NEXT:    .cfi_offset w27, -24
+; CHECK-NEXT:    .cfi_offset w28, -32
+; CHECK-NEXT:    .cfi_offset b8, -40
+; CHECK-NEXT:    .cfi_offset b9, -48
+; CHECK-NEXT:    .cfi_offset b10, -56
+; CHECK-NEXT:    .cfi_offset b11, -64
+; CHECK-NEXT:    .cfi_offset b12, -72
+; CHECK-NEXT:    .cfi_offset b13, -80
+; CHECK-NEXT:    .cfi_offset b14, -88
+; CHECK-NEXT:    .cfi_offset b15, -96
+; CHECK-NEXT:    .cfi_remember_state
+; CHECK-NEXT:    sub x9, sp, #160
+; CHECK-NEXT:    and sp, x9, #0xffffffffffffff00
+; CHECK-NEXT:  Lloh0:
+; CHECK-NEXT:    adrp x8, ___stack_chk_guard@GOTPAGE
+; CHECK-NEXT:  Lloh1:
+; CHECK-NEXT:    ldr x8, [x8, ___stack_chk_guard@GOTPAGEOFF]
+; CHECK-NEXT:  Lloh2:
+; CHECK-NEXT:    ldr x8, [x8]
+; CHECK-NEXT:    str x8, [sp, #152]
+; CHECK-NEXT:    mov z0.b, #0 ; =0x0
+; CHECK-NEXT:    stp q0, q0, [sp, #32]
+; CHECK-NEXT:    stp q0, q0, [sp]
+; CHECK-NEXT:    mov x8, sp
+; CHECK-NEXT:    ; InlineAsm Start
+; CHECK-NEXT:    ptrue p0.s
+; CHECK-NEXT:    st1w { z0.s }, p0, [x8]
+; CHECK-EMPTY:
+; CHECK-NEXT:    ; InlineAsm End
+; CHECK-NEXT:    ldr x8, [sp, #152]
+; CHECK-NEXT:  Lloh3:
+; CHECK-NEXT:    adrp x9, ___stack_chk_guard@GOTPAGE
+; CHECK-NEXT:  Lloh4:
+; CHECK-NEXT:    ldr x9, [x9, ___stack_chk_guard@GOTPAGEOFF]
+; CHECK-NEXT:  Lloh5:
+; CHECK-NEXT:    ldr x9, [x9]
+; CHECK-NEXT:    cmp x9, x8
+; CHECK-NEXT:    b.ne LBB1_2
+; CHECK-NEXT:  ; %bb.1: ; %entry
+; CHECK-NEXT:    sub sp, x29, #80
+; CHECK-NEXT:    .cfi_def_cfa wsp, 96
+; CHECK-NEXT:    ldp x29, x30, [sp, #80] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp x28, x27, [sp, #64] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d9, d8, [sp, #48] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d11, d10, [sp, #32] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d13, d12, [sp, #16] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldp d15, d14, [sp], #96 ; 16-byte Folded Reload
+; CHECK-NEXT:    .cfi_def_cfa_offset 0
+; CHECK-NEXT:    .cfi_restore w30
+; CHECK-NEXT:    .cfi_restore w29
+; CHECK-NEXT:    .cfi_restore w27
+; CHECK-NEXT:    .cfi_restore w28
+; CHECK-NEXT:    .cfi_restore b8
+; CHECK-NEXT:    .cfi_restore b9
+; CHECK-NEXT:    .cfi_restore b10
+; CHECK-NEXT:    .cfi_restore b11
+; CHECK-NEXT:    .cfi_restore b12
+; CHECK-NEXT:    .cfi_restore b13
+; CHECK-NEXT:    .cfi_restore b14
+; CHECK-NEXT:    .cfi_restore b15
+; CHECK-NEXT:    ret
+; CHECK-NEXT:  LBB1_2: ; %entry
+; CHECK-NEXT:    .cfi_restore_state
+; CHECK-NEXT:    smstop sm
+; CHECK-NEXT:    bl ___stack_chk_fail
+; CHECK-NEXT:    smstart sm
+; CHECK-NEXT:    .loh AdrpLdrGotLdr Lloh3, Lloh4, Lloh5
+; CHECK-NEXT:    .loh AdrpLdrGotLdr Lloh0, Lloh1, Lloh2
+entry:
+  %uu = alloca [16 x float], align 256
+  call void @llvm.lifetime.start.p0(i64 64, ptr nonnull %uu) #5
+  call void @llvm.memset.p0.i64(ptr noundef nonnull align 256 dereferenceable(64) %uu, i8 0, i64 64, i1 false)
+  call void asm sideeffect "ptrue p0.s\0Ast1w { z0.s }, p0, [$0]\0A", "r"(ptr nonnull %uu) #5
+  call void @llvm.lifetime.end.p0(i64 64, ptr nonnull %uu) #5
+  ret void
+}
+
+; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #2
+
+; Function Attrs: mustprogress nocallback nofree nounwind willreturn memory(argmem: write)
+declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg) #3
+
+; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #2
+
+attributes #0 = { mustprogress norecurse nounwind ssp uwtable(sync) "stack-protector-buffer-size"="8" "target-cpu"="apple-a16" "target-features"="+sme,+sme-f64f64,+sme2" }
+attributes #1 = { mustprogress norecurse nounwind ssp uwtable(sync) "aarch64_pstate_sm_enabled" "stack-protector-buffer-size"="8" "target-cpu"="apple-a16" "target-features"="+sme,+sme-f64f64,+sme2" }
+attributes #2 = { mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
+attributes #3 = { mustprogress nocallback nofree nounwind willreturn memory(argmem: write) }
+attributes #4 = { "aarch64_pstate_sm_enabled" "no-builtin-calloc" "no-builtin-stpcpy" }
+attributes #5 = { nounwind }