[AArch64] Allow variadic calls with SVE argument if it is named. (#136833)

The following case used to work:

  void foo(svint32_t a, ...);
  void bar(svint32_t a) { foo(a); }

but 6c9086d introduced a regression
that wasn't caught by the existing test `sve-varargs.ll` because the
call in the test wasn't a tail call and therefore skipped the code-path
with the `report_fatal_error`.

Author: sdesmalen-arm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -8592,6 +8592,10 @@ static bool callConvSupportsVarArgs(CallingConv::ID CC) {
   switch (CC) {
   case CallingConv::C:
   case CallingConv::PreserveNone:
+  // SVE vector call is only partially supported, but it should
+  // support named arguments being passed. Any arguments being passed
+  // as varargs, are still unsupported.
+  case CallingConv::AArch64_SVE_VectorCall:
     return true;
   default:
     return false;

llvm/test/CodeGen/AArch64/sve-varargs-caller-broken.ll

@@ -1,11 +1,24 @@
-; RUN: not --crash llc -mtriple aarch64-linux-gnu -mattr=+sve <%s 2>&1 | FileCheck %s
+; RUN: split-file %s %t
 
-declare i32 @sve_printf(ptr, <vscale x 4 x i32>, ...)
+; RUN: not --crash llc -mtriple aarch64-linux-gnu -mattr=+sve < %t/test-non-tailcall.ll 2>&1 | FileCheck %s --check-prefix=CHECKNONTAIL
+; RUN: not --crash llc -mtriple aarch64-linux-gnu -mattr=+sve < %t/test-tailcall.ll 2>&1 | FileCheck %s --check-prefix=CHECKTAIL
 
+;--- test-non-tailcall.ll
+declare i32 @sve_printf(ptr, <vscale x 4 x i32>, ...)
 @.str_1 = internal constant [6 x i8] c"boo!\0A\00"
 
-; CHECK: Passing SVE types to variadic functions is currently not supported
-define void @foo(<vscale x 4 x i32> %x) {
+; CHECKTAIL: Passing SVE types to variadic functions is currently not supported
+define void @foo_nontail(<vscale x 4 x i32> %x) {
   call i32 (ptr, <vscale x 4 x i32>, ...) @sve_printf(ptr @.str_1, <vscale x 4 x i32> %x, <vscale x 4 x i32> %x)
   ret void
 }
+
+;--- test-tailcall.ll
+declare i32 @sve_printf(ptr, <vscale x 4 x i32>, ...)
+@.str_1 = internal constant [6 x i8] c"boo!\0A\00"
+
+; CHECKNONTAIL: Passing SVE types to variadic functions is currently not supported
+define void @foo_tail(<vscale x 4 x i32> %x) {
+  tail call i32 (ptr, <vscale x 4 x i32>, ...) @sve_printf(ptr @.str_1, <vscale x 4 x i32> %x, <vscale x 4 x i32> %x)
+  ret void
+}

llvm/test/CodeGen/AArch64/sve-varargs.ll

@@ -5,8 +5,8 @@ declare i32 @sve_printf(ptr, <vscale x 4 x i32>, ...)
 
 @.str_1 = internal constant [6 x i8] c"boo!\0A\00"
 
-define void @foo(<vscale x 4 x i32> %x) uwtable {
-; CHECK-LABEL: foo:
+define void @foo_nontail(<vscale x 4 x i32> %x) uwtable {
+; CHECK-LABEL: foo_nontail:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
@@ -21,3 +21,13 @@ define void @foo(<vscale x 4 x i32> %x) uwtable {
   call i32 (ptr, <vscale x 4 x i32>, ...) @sve_printf(ptr @.str_1, <vscale x 4 x i32> %x)
   ret void
 }
+
+define void @foo_tail(<vscale x 4 x i32> %x) uwtable {
+; CHECK-LABEL: foo_tail:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    adrp x0, .str_1
+; CHECK-NEXT:    add x0, x0, :lo12:.str_1
+; CHECK-NEXT:    b sve_printf
+  tail call i32 (ptr, <vscale x 4 x i32>, ...) @sve_printf(ptr @.str_1, <vscale x 4 x i32> %x)
+  ret void
+}