AArch64: Use reportFatalUsageError for unsupported calling conv (#144840)

This probably should emit a DiagnosticInfoUnsupported and use the
default calling convention instead, but then we would need to pass
in the context.

Also move where CCAssignFnForCall is called. It was unnecessarily
called for each argument, so the error wouldn't trigger for functions
with 0 arguments.

This only ensures the error occurs for functions defined with the
calling convention. The error is still missed for outgoing calls
with no arguments. The lowering logic here is convoluted, calling
CCAssignFnForCall for each argument and it does not mirror
LowerFormalArguments so I'm not sure what's going on here.

Author: arsenm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -7632,7 +7632,7 @@ CCAssignFn *AArch64TargetLowering::CCAssignFnForCall(CallingConv::ID CC,
                                                      bool IsVarArg) const {
   switch (CC) {
   default:
-    report_fatal_error("Unsupported calling convention.");
+    reportFatalUsageError("unsupported calling convention");
   case CallingConv::GHC:
     return CC_AArch64_GHC;
   case CallingConv::PreserveNone:
@@ -7741,6 +7741,12 @@ SDValue AArch64TargetLowering::LowerFormalArguments(
   unsigned NumArgs = Ins.size();
   Function::const_arg_iterator CurOrigArg = F.arg_begin();
   unsigned CurArgIdx = 0;
+  bool UseVarArgCC = false;
+  if (IsWin64)
+    UseVarArgCC = isVarArg;
+
+  CCAssignFn *AssignFn = CCAssignFnForCall(CallConv, UseVarArgCC);
+
   for (unsigned i = 0; i != NumArgs; ++i) {
     MVT ValVT = Ins[i].VT;
     if (Ins[i].isOrigArg()) {
@@ -7757,10 +7763,6 @@ SDValue AArch64TargetLowering::LowerFormalArguments(
       else if (ActualMVT == MVT::i16)
         ValVT = MVT::i16;
     }
-    bool UseVarArgCC = false;
-    if (IsWin64)
-      UseVarArgCC = isVarArg;
-    CCAssignFn *AssignFn = CCAssignFnForCall(CallConv, UseVarArgCC);
     bool Res =
         AssignFn(i, ValVT, ValVT, CCValAssign::Full, Ins[i].Flags, CCInfo);
     assert(!Res && "Call operand has unhandled type");
@@ -8429,6 +8431,8 @@ static void analyzeCallOperands(const AArch64TargetLowering &TLI,
         ArgVT = MVT::i16;
     }
 
+    // FIXME: CCAssignFnForCall should be called once, for the call and not per
+    // argument. This logic should exactly mirror LowerFormalArguments.
     CCAssignFn *AssignFn = TLI.CCAssignFnForCall(CalleeCC, UseVarArgCC);
     bool Res = AssignFn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, CCInfo);
     assert(!Res && "Call operand has unhandled type");

llvm/test/CodeGen/AArch64/unsupported-cc-call.ll

@@ -0,0 +1,8 @@
+; FIXME: This should error:
+; RUN: llc -mtriple=aarch64-- -filetype=null %s
+declare amdgpu_gfx void @amdgpu_gfx_func()
+
+define void @call_amdgpu_gfx_func() {
+  call amdgpu_gfx void @amdgpu_gfx_func()
+  ret void
+}

llvm/test/CodeGen/AArch64/unsupported-cc-func.ll

@@ -0,0 +1,6 @@
+; RUN: not llc -mtriple=aarch64-- -filetype=null %s 2>&1 | FileCheck %s
+
+; CHECK: LLVM ERROR: unsupported calling convention
+define amdgpu_gfx void @amdgpu_gfx_func_definition() {
+  ret void
+}

llvm/test/MC/AArch64/coff-function-type-info.ll

@@ -1,10 +1,10 @@
-; RUN: llc -mtriple arm64-windows -filetype asm -o - %s \
+    ; RUN: llc -mtriple arm64-windows -filetype asm -o - %s \
 ; RUN:    | FileCheck %s -check-prefix CHECK-ASM
 
 ; RUN: llc -mtriple arm64-windows -filetype obj -o - %s \
 ; RUN:    | llvm-readobj --symbols - | FileCheck %s -check-prefix CHECK-OBJECT
 
-define arm_aapcs_vfpcc void @external() {
+define aarch64_vector_pcs void @external() {
 entry:
   ret void
 }
@@ -15,7 +15,7 @@ entry:
 ; CHECK-ASM: .endef
 ; CHECK-ASM: .globl external
 
-define internal arm_aapcs_vfpcc void @internal() {
+define internal aarch64_vector_pcs void @internal() {
 entry:
   ret void
 }