[llvm] [AArch64][SME] Return false from produceCompactUnwindFrame if VG save required. (PR #104588)

[Kerry McLaughlin via llvm-commits]

https://github.com/kmclaughlin-arm created https://github.com/llvm/llvm-project/pull/104588

The compact unwind format requires all registers are stored in pairs, so
return false from produceCompactUnwindFrame if we require saving VG.

>From 78ac8cb9fe12d0b001b8c8c54c915e14f80270d0 Mon Sep 17 00:00:00 2001
From: Kerry McLaughlin <kerry.mclaughlin at arm.com>
Date: Thu, 15 Aug 2024 15:19:21 +0000
Subject: [PATCH] [AArch64][SME] Return false from produceCompactUnwindFrame if
 VG save required.

The compact unwind format requires all registers are stored in pairs, so
return false from produceCompactUnwindFrame if we require saving VG.
---
 .../Target/AArch64/AArch64FrameLowering.cpp   |  3 +-
 .../test/CodeGen/AArch64/sme-darwin-sve-vg.ll | 55 +++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/AArch64/sme-darwin-sve-vg.ll

diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 429affed63497d..e0f8853b715354 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -2860,7 +2860,8 @@ static bool produceCompactUnwindFrame(MachineFunction &MF) {
   return Subtarget.isTargetMachO() &&
          !(Subtarget.getTargetLowering()->supportSwiftError() &&
            Attrs.hasAttrSomewhere(Attribute::SwiftError)) &&
-         MF.getFunction().getCallingConv() != CallingConv::SwiftTail;
+         MF.getFunction().getCallingConv() != CallingConv::SwiftTail &&
+         !requiresSaveVG(MF);
 }
 
 static bool invalidateWindowsRegisterPairing(unsigned Reg1, unsigned Reg2,
diff --git a/llvm/test/CodeGen/AArch64/sme-darwin-sve-vg.ll b/llvm/test/CodeGen/AArch64/sme-darwin-sve-vg.ll
new file mode 100644
index 00000000000000..c32e9cbc053939
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/sme-darwin-sve-vg.ll
@@ -0,0 +1,55 @@
+; RUN: llc -mtriple=aarch64-darwin -mattr=+sve -mattr=+sme -verify-machineinstrs < %s | FileCheck %s
+
+declare void @normal_callee();
+
+define void @locally_streaming_fn() #0 {
+; CHECK-LABEL: locally_streaming_fn:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    stp d15, d14, [sp, #-96]! ; 16-byte Folded Spill
+; CHECK-NEXT:    .cfi_def_cfa_offset 96
+; CHECK-NEXT:    rdsvl x9, #1
+; CHECK-NEXT:    stp d13, d12, [sp, #16] ; 16-byte Folded Spill
+; CHECK-NEXT:    lsr x9, x9, #3
+; 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 x30, x9, [sp, #64] ; 16-byte Folded Spill
+; CHECK-NEXT:    cntd x9
+; CHECK-NEXT:    str x9, [sp, #80] ; 8-byte Folded Spill
+; CHECK-NEXT:    .cfi_offset vg, -16
+; CHECK-NEXT:    .cfi_offset w30, -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:    smstart sm
+; CHECK-NEXT:    .cfi_offset vg, -24
+; CHECK-NEXT:    smstop sm
+; CHECK-NEXT:    bl _normal_callee
+; CHECK-NEXT:    smstart sm
+; CHECK-NEXT:    .cfi_restore vg
+; CHECK-NEXT:    smstop sm
+; CHECK-NEXT:    ldp d9, d8, [sp, #48] ; 16-byte Folded Reload
+; CHECK-NEXT:    ldr x30, [sp, #64] ; 8-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 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
+  call void @normal_callee()
+  ret void
+}
+
+attributes #0 = { "aarch64_pstate_sm_body" uwtable(async) }