https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054
Bug ID: 115054
Summary: __float128 and _Float16 use incorrect ABI on x86-64
MinGW
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: tmgross at umich dot edu
Target Milestone: ---
GCC appears to try to pass half and quad-precision floating point numbers
(_Float16 and __float128) using the integer calling convention on x86-64 MinGW.
They should get passed with the floating point CC in SSE registers, like other
floats, as is done by GCC x86-64 linux, Clang x86-64 linux, and Clang x86-64
MinGW.
Sample:
void f16_ext(_Float16);
void f16_entry(float _, _Float16 a) {
asm("nop # marker");
f16_ext(a);
}
void f32_ext(float);
void f32_entry(float _, float a) {
asm("nop # marker");
f32_ext(a);
}
void f64_ext(double);
void f64_entry(float _, double a) {
asm("nop # marker");
f64_ext(a);
}
void f128_ext(__float128);
void f128_entry(float _, __float128 a) {
asm("nop # marker");
f128_ext(a);
}
Incorrect output from GCC on x64 MinGW (O2):
f16_entry:
mov ecx, edx
nop # marker
jmp f16_ext
f32_entry:
movaps xmm0, xmm1
nop # marker
jmp f32_ext
f64_entry:
movapd xmm0, xmm1
nop # marker
jmp f64_ext
f128_entry:
sub rsp, 56
movdqa xmm0, XMMWORD PTR [rdx]
nop # marker
lea rcx, 32[rsp]
movaps XMMWORD PTR 32[rsp], xmm0
call f128_ext
nop
add rsp, 56
ret
Correct output from GCC on x64 Linux (O2):
f16_entry:
movaps xmm0, xmm1
nop # marker
jmp f16_ext
f32_entry:
movaps xmm0, xmm1
nop # marker
jmp f32_ext
f64_entry:
movapd xmm0, xmm1
nop # marker
jmp f64_ext
f128_entry:
movdqa xmm0, xmm1
nop # marker
jmp f128_ext
Correct output from Clang on both x64 Linux and x64 MinGW:
f16_entry: # @f16_entry
movaps xmm0, xmm1
nop # marker
jmp f16_ext # TAILCALL
f32_entry: # @f32_entry
movaps xmm0, xmm1
nop # marker
jmp f32_ext # TAILCALL
f64_entry: # @f64_entry
movaps xmm0, xmm1
nop # marker
jmp f64_ext # TAILCALL
f128_entry: # @f128_entry
movaps xmm0, xmm1
nop # marker
jmp f128_ext # TAILCALL
Tested with GCC 13.1. Link: https://gcc.godbolt.org/z/hdojahes5
