[RISCV] Fix passing two floating-point values in complex separately by two GPRs on RV64

Summary:
This patch fixed the error of counting the remaining FPRs. Complex floating-point
values should be passed by two FPRs for the hard-float ABI. If no two FPRs are
available, it should be passed via a 64-bit GPR (fp+fp). `ArgFPRsLeft` is only
decreased one while the type is complex floating-point. It causes two floating-point
values in the complex are passed separately by two GPRs.

Reviewers: asb, luismarques, lenary

Reviewed By: asb

Subscribers: rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, jrtc27, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, psnobl, benna, s.egerton, pzheng, sameer.abuasal, apazos, evandro, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D79770

(cherry picked from commit 7ee479a)

Author: tclin914

clang/lib/CodeGen/TargetInfo.cpp

@@ -9613,7 +9613,8 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
   uint64_t Size = getContext().getTypeSize(Ty);
 
   // Pass floating point values via FPRs if possible.
-  if (IsFixed && Ty->isFloatingType() && FLen >= Size && ArgFPRsLeft) {
+  if (IsFixed && Ty->isFloatingType() && !Ty->isComplexType() &&
+      FLen >= Size && ArgFPRsLeft) {
     ArgFPRsLeft--;
     return ABIArgInfo::getDirect();
   }

clang/test/CodeGen/riscv64-lp64-abi.c

@@ -30,3 +30,24 @@ struct large f_scalar_stack_2(double a, __int128_t b, long double c, v32i8 d,
                               uint8_t e, int8_t f, uint8_t g) {
   return (struct large){a, e, f, g};
 }
+
+// Complex floating-point values or structs containing a single complex
+// floating-point value should be passed in a GPR.
+
+// CHECK: define void @f_floatcomplex(i64 %a.coerce)
+void f_floatcomplex(float __complex__ a) {}
+
+// CHECK: define i64 @f_ret_floatcomplex()
+float __complex__ f_ret_floatcomplex() {
+  return 1.0;
+}
+
+struct floatcomplex_s { float __complex__ c; };
+
+// CHECK: define void @f_floatcomplex_s_arg(i64 %a.coerce)
+void f_floatcomplex_s_arg(struct floatcomplex_s a) {}
+
+// CHECK: define i64 @f_ret_floatcomplex_s()
+struct floatcomplex_s f_ret_floatcomplex_s() {
+  return (struct floatcomplex_s){1.0};
+}

clang/test/CodeGen/riscv64-lp64f-lp64d-abi.c

@@ -165,6 +165,35 @@ struct floatcomplex_s f_ret_floatcomplex_s() {
   return (struct floatcomplex_s){1.0};
 }
 
+// Complex floating-point values or structs containing a single complex
+// floating-point value should be passed in GPRs if no two FPRs is available.
+
+// CHECK: define void @f_floatcomplex_insufficient_fprs1(float %a.coerce0, float %a.coerce1, float %b.coerce0, float %b.coerce1, float %c.coerce0, float %c.coerce1, float %d.coerce0, float %d.coerce1, i64 %e.coerce)
+void f_floatcomplex_insufficient_fprs1(float __complex__ a, float __complex__ b,
+                                       float __complex__ c, float __complex__ d,
+                                       float __complex__ e) {}
+
+
+// CHECK: define void @f_floatcomplex_s_arg_insufficient_fprs1(float %0, float %1, float %2, float %3, float %4, float %5, float %6, float %7, i64 %e.coerce)
+void f_floatcomplex_s_arg_insufficient_fprs1(struct floatcomplex_s a,
+                                             struct floatcomplex_s b,
+                                             struct floatcomplex_s c,
+                                             struct floatcomplex_s d,
+                                             struct floatcomplex_s e) {}
+
+// CHECK: define void @f_floatcomplex_insufficient_fprs2(float %a, float %b.coerce0, float %b.coerce1, float %c.coerce0, float %c.coerce1, float %d.coerce0, float %d.coerce1, i64 %e.coerce)
+void f_floatcomplex_insufficient_fprs2(float a,
+                                       float __complex__ b, float __complex__ c,
+                                       float __complex__ d, float __complex__ e) {}
+
+
+// CHECK: define void @f_floatcomplex_s_arg_insufficient_fprs2(float %a, float %0, float %1, float %2, float %3, float %4, float %5, i64 %e.coerce)
+void f_floatcomplex_s_arg_insufficient_fprs2(float a,
+                                             struct floatcomplex_s b,
+                                             struct floatcomplex_s c,
+                                             struct floatcomplex_s d,
+                                             struct floatcomplex_s e) {}
+
 // Test single or two-element structs that need flattening. e.g. those
 // containing nested structs, floats in small arrays, zero-length structs etc.