[AArch64][SME] Add calling convention for calls to __arm_get_current_vg

Adds a calling convention for calls to the __arm_get_current_vg support
routine, which preserves X1-X15, X19-X29, SP, Z0-Z31 & P0-P15.

See ARM-software/abi-aa#263

llvm/include/llvm/AsmParser/LLToken.h

@@ -146,6 +146,7 @@ enum Kind {
   kw_aarch64_vector_pcs,
   kw_aarch64_sve_vector_pcs,
   kw_aarch64_sme_preservemost_from_x0,
+  kw_aarch64_sme_preservemost_from_x1,
   kw_aarch64_sme_preservemost_from_x2,
   kw_msp430_intrcc,
   kw_avr_intrcc,

llvm/include/llvm/IR/CallingConv.h

@@ -267,6 +267,9 @@ namespace CallingConv {
     /// Calling convention used for RISC-V V-extension.
     RISCV_VectorCall = 110,
 
+    /// Preserve X1-X15, X19-X29, SP, Z0-Z31, P0-P15.
+    AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1 = 111,
+
     /// The highest possible ID. Must be some 2^k - 1.
     MaxID = 1023
   };

llvm/lib/AsmParser/LLLexer.cpp

@@ -603,6 +603,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(aarch64_vector_pcs);
   KEYWORD(aarch64_sve_vector_pcs);
   KEYWORD(aarch64_sme_preservemost_from_x0);
+  KEYWORD(aarch64_sme_preservemost_from_x1);
   KEYWORD(aarch64_sme_preservemost_from_x2);
   KEYWORD(msp430_intrcc);
   KEYWORD(avr_intrcc);

llvm/lib/AsmParser/LLParser.cpp

@@ -2153,6 +2153,7 @@ void LLParser::parseOptionalDLLStorageClass(unsigned &Res) {
 ///   ::= 'aarch64_vector_pcs'
 ///   ::= 'aarch64_sve_vector_pcs'
 ///   ::= 'aarch64_sme_preservemost_from_x0'
+///   ::= 'aarch64_sme_preservemost_from_x1'
 ///   ::= 'aarch64_sme_preservemost_from_x2'
 ///   ::= 'msp430_intrcc'
 ///   ::= 'avr_intrcc'
@@ -2212,6 +2213,9 @@ bool LLParser::parseOptionalCallingConv(unsigned &CC) {
   case lltok::kw_aarch64_sme_preservemost_from_x0:
     CC = CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0;
     break;
+  case lltok::kw_aarch64_sme_preservemost_from_x1:
+    CC = CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1;
+    break;
   case lltok::kw_aarch64_sme_preservemost_from_x2:
     CC = CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2;
     break;

llvm/lib/IR/AsmWriter.cpp

@@ -326,6 +326,9 @@ static void PrintCallingConv(unsigned cc, raw_ostream &Out) {
   case CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0:
     Out << "aarch64_sme_preservemost_from_x0";
     break;
+  case CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1:
+    Out << "aarch64_sme_preservemost_from_x1";
+    break;
   case CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2:
     Out << "aarch64_sme_preservemost_from_x2";
     break;

llvm/lib/Target/AArch64/AArch64CallingConvention.td

@@ -563,6 +563,14 @@ def CSR_AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0
                                                  (sequence "X%u",19, 28),
                                                  LR, FP)>;
 
+// SME ABI support routines such as __arm_get_current_vg preserve most registers.
+def CSR_AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1
+                          : CalleeSavedRegs<(add (sequence "Z%u", 0, 31),
+                                                 (sequence "P%u", 0, 15),
+                                                 (sequence "X%u", 1, 15),
+                                                 (sequence "X%u",19, 28),
+                                                 LR, FP)>;
+
 // SME ABI support routines __arm_sme_state preserves most registers.
 def CSR_AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2
                           : CalleeSavedRegs<(add (sequence "Z%u", 0, 31),

llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp

@@ -108,6 +108,12 @@ AArch64RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
         "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0 is "
         "only supported to improve calls to SME ACLE save/restore/disable-za "
         "functions, and is not intended to be used beyond that scope.");
+  if (MF->getFunction().getCallingConv() ==
+          CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1)
+    report_fatal_error(
+        "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1 is "
+        "only supported to improve calls to SME ACLE __arm_get_current_vg function, "
+        "and is not intended to be used beyond that scope.");
   if (MF->getFunction().getCallingConv() ==
           CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2)
     report_fatal_error(
@@ -154,6 +160,12 @@ AArch64RegisterInfo::getDarwinCalleeSavedRegs(const MachineFunction *MF) const {
         "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0 is "
         "only supported to improve calls to SME ACLE save/restore/disable-za "
         "functions, and is not intended to be used beyond that scope.");
+  if (MF->getFunction().getCallingConv() ==
+          CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1)
+    report_fatal_error(
+        "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1 is "
+        "only supported to improve calls to SME ACLE __arm_get_current_vg function, "
+        "and is not intended to be used beyond that scope.");
   if (MF->getFunction().getCallingConv() ==
           CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2)
     report_fatal_error(
@@ -236,6 +248,10 @@ AArch64RegisterInfo::getDarwinCallPreservedMask(const MachineFunction &MF,
     report_fatal_error(
         "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0 is "
         "unsupported on Darwin.");
+  if (CC == CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1)
+    report_fatal_error(
+        "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1 is "
+        "unsupported on Darwin.");
   if (CC == CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2)
     report_fatal_error(
         "Calling convention AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2 is "
@@ -281,6 +297,8 @@ AArch64RegisterInfo::getCallPreservedMask(const MachineFunction &MF,
                : CSR_AArch64_SVE_AAPCS_RegMask;
   if (CC == CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0)
     return CSR_AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0_RegMask;
+  if (CC == CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1)
+    return CSR_AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1_RegMask;
   if (CC == CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2)
     return CSR_AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2_RegMask;
   if (CC == CallingConv::CFGuard_Check)
@@ -640,6 +658,7 @@ bool AArch64RegisterInfo::isArgumentRegister(const MachineFunction &MF,
   case CallingConv::AArch64_VectorCall:
   case CallingConv::AArch64_SVE_VectorCall:
   case CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X0:
+  case CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X1:
   case CallingConv::AArch64_SME_ABI_Support_Routines_PreserveMost_From_X2:
     if (STI.isTargetWindows())
       return HasReg(CC_AArch64_Win64PCS_ArgRegs, Reg);

llvm/test/CodeGen/AArch64/sme-support-routines-calling-convention.ll

@@ -18,6 +18,20 @@ define void @test_sme_calling_convention_x0() nounwind {
   ret void
 }
 
+define i64 @test_sme_calling_convention_x1() nounwind {
+; CHECK-LABEL: test_sme_calling_convention_x1:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
+; CHECK-NEXT:    bl __arm_get_current_vg
+; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
+; CHECK-NEXT:    ret
+;
+; CHECK-CSRMASK-LABEL: name: test_sme_calling_convention_x1
+; CHECK-CSRMASK: BL @__arm_get_current_vg, csr_aarch64_sme_abi_support_routines_preservemost_from_x1
+  %vg = call aarch64_sme_preservemost_from_x1 i64 @__arm_get_current_vg()
+  ret i64 %vg
+}
+
 define i64 @test_sme_calling_convention_x2() nounwind {
 ; CHECK-LABEL: test_sme_calling_convention_x2:
 ; CHECK:       // %bb.0:
@@ -34,4 +48,5 @@ define i64 @test_sme_calling_convention_x2() nounwind {
 }
 
 declare void @__arm_tpidr2_save()
+declare i64 @__arm_get_current_vg()
 declare {i64, i64} @__arm_sme_state()