[ARM][GISel] Treat calls as variadic even if only fixed arguments provided

[ostannard]

Summary

For the ARM hard-float calling convention, calls to variadic functions need to be treated differently, even if only the fixed arguments are provided.

This fixes GCC-C-execute-pr68390 in the test-suite, which is failing on the ARM GlobaISel bot.

[ostannard]

Ping.

[yroux]

LGTM

[ostannard]

Committed as rG3676ef1053.

llvm/lib/Target/ARM/ARMCallLowering.cpp

 
   MIB.addRegMask(TRI->getCallPreservedMask(MF, Info.CallConv));
 
-  bool IsVarArg = false;
   SmallVector<ArgInfo, 8> ArgInfos;
   for (auto Arg : Info.OrigArgs) {
     if (!isSupportedType(DL, TLI, Arg.Ty))
       return false;
 
-    if (!Arg.IsFixed)
-      IsVarArg = true;
-
     if (Arg.Flags[0].isByVal())
       return false;
 
     splitToValueTypes(Arg, ArgInfos, MF);
   }
 
-  auto ArgAssignFn = TLI.CCAssignFnForCall(Info.CallConv, IsVarArg);
+  auto ArgAssignFn = TLI.CCAssignFnForCall(Info.CallConv, Info.IsVarArg);
   ARMOutgoingValueHandler ArgHandler(MIRBuilder, MRI, MIB, ArgAssignFn);
   if (!handleAssignments(MIRBuilder, ArgInfos, ArgHandler))
     return false;

 
     ArgInfos.clear();
     splitToValueTypes(Info.OrigRet, ArgInfos, MF);
-    auto RetAssignFn = TLI.CCAssignFnForReturn(Info.CallConv, IsVarArg);
+    auto RetAssignFn = TLI.CCAssignFnForReturn(Info.CallConv, Info.IsVarArg);
     CallReturnHandler RetHandler(MIRBuilder, MRI, MIB, RetAssignFn);
     if (!handleAssignments(MIRBuilder, ArgInfos, RetHandler))
       return false;

llvm/test/CodeGen/ARM/GlobalISel/irtranslator-varargs-lowering.ll

   ret float %r
 }
 
+define arm_aapcs_vfpcc float @test_call_to_varargs_with_floats_fixed_args_only(float %a, double %b) {
+; CHECK-LABEL: name: test_call_to_varargs_with_floats_fixed_args_only
+; CHECK-DAG: [[AVREG:%[0-9]+]]:_(s32) = COPY $s0
+; CHECK-DAG: [[BVREG:%[0-9]+]]:_(s64) = COPY $d1
+; CHECK: ADJCALLSTACKDOWN 0, 0, 14 /* CC::al */, $noreg, implicit-def $sp, implicit $sp
+; CHECK-DAG: $r0 = COPY [[AVREG]]
+; CHECK-DAG: [[B1:%[0-9]+]]:_(s32), [[B2:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[BVREG]](s64)
+; CHECK-DAG: $r2 = COPY [[B1]]
+; CHECK-DAG: $r3 = COPY [[B2]]
+; ARM: BL @float_varargs_target, csr_aapcs, implicit-def $lr, implicit $sp, implicit $r0, implicit $r2, implicit $r3, implicit-def $r0
+; THUMB: tBL 14 /* CC::al */, $noreg, @float_varargs_target, csr_aapcs, implicit-def $lr, implicit $sp, implicit $r0, implicit $r2, implicit $r3, implicit-def $r0
+; CHECK: [[RVREG:%[0-9]+]]:_(s32) = COPY $r0
+; CHECK: ADJCALLSTACKUP 0, 0, 14 /* CC::al */, $noreg, implicit-def $sp, implicit $sp
+; CHECK: $s0 = COPY [[RVREG]]
+; ARM: BX_RET 14 /* CC::al */, $noreg, implicit $s0
+; THUMB: tBX_RET 14 /* CC::al */, $noreg, implicit $s0
+entry:
+  %r = notail call arm_aapcs_vfpcc float(float, double, ...) @float_varargs_target(float %a, double %b)
+  ret float %r
+}
+
 define arm_aapcs_vfpcc float @test_indirect_call_to_varargs(float (float, double, ...) *%fptr, float %a, double %b) {
 ; CHECK-LABEL: name: test_indirect_call_to_varargs
 ; CHECK-DAG: [[FPTRVREG:%[0-9]+]]:gpr(p0) = COPY $r0