[Bug target/102143] ABI incompatibility with clang when passing 32bit vectors on 32bit i686
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143
--- Comment #6 from H.J. Lu ---
I think psABIs should specify how to pass and return 8-bit, 16-bit and 32-bit
vectors. We can treat them as
struct vectorN
{
intN
};
[Bug target/102143] ABI incompatibility with clang when passing 32bit vectors on 32bit i686
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143 --- Comment #5 from Uroš Bizjak --- (In reply to Uroš Bizjak from comment #3) > gcc has also some problems in this area. With -mregparm=3, one would expect > arguments obeying integer ABI to be passed in registers, but regparm flag > has no effect and the same code is produced: > > foo: > movd4(%esp), %xmm0 > movd8(%esp), %xmm1 > paddw %xmm1, %xmm0 > movd%xmm0, %eax > ret (sorry, sent the message too fast) However, with -mno-sse -mregparm=3, regparm does have effect and produces: foo: leal(%eax,%edx), %ecx sarl$16, %eax sarl$16, %edx addl%eax, %edx movzwl %cx, %eax sall$16, %edx orl %edx, %eax ret vs -mno-sse -mregparm=0: foo: movl4(%esp), %edx movl8(%esp), %ecx leal(%edx,%ecx), %eax sarl$16, %edx sarl$16, %ecx addl%ecx, %edx movzwl %ax, %eax sall$16, %edx orl %edx, %eax ret
[Bug target/102143] ABI incompatibility with clang when passing 32bit vectors on 32bit i686
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143
--- Comment #4 from Jakub Jelinek ---
Well, we already have the ABI ISA dependent,
typedef int __v8si __attribute__((__vector_size__ (32)));
__v8si
foo (__v8si x, __v8si y)
{
return x + y;
}
has different ABI based on -mavx or -mno-avx, etc. For -mno-avx we emit a
warning:
/tmp/test.c: In function ‘foo’:
/tmp/test.c:5:1: warning: AVX vector return without AVX enabled changes the ABI
[-Wpsabi]
5 | {
| ^
/tmp/test.c:4:1: note: the ABI for passing parameters with 32-byte alignment
has changed in GCC 4.6
4 | foo (__v8si x, __v8si y)
| ^~~
/tmp/test.c:4:1: warning: AVX vector argument without AVX enabled changes the
ABI [-Wpsabi]
So, depending on what we decide, if the ABI will be ISA dependent, we want a
warning like the above one.
[Bug target/102143] ABI incompatibility with clang when passing 32bit vectors on 32bit i686
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143 --- Comment #3 from Uroš Bizjak --- gcc has also some problems in this area. With -mregparm=3, one would expect arguments obeying integer ABI to be passed in registers, but regparm flag has no effect and the same code is produced: foo: movd4(%esp), %xmm0 movd8(%esp), %xmm1 paddw %xmm1, %xmm0 movd%xmm0, %eax ret
[Bug target/102143] ABI incompatibility with clang when passing 32bit vectors on 32bit i686
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143 --- Comment #2 from Uroš Bizjak --- (In reply to H.J. Lu from comment #1) > 16-bit and 32-bit vector pass and return are not specified in i386 psABI. > 64-bit vector is specified, not really usable. Any suggestions? With -mno-sse, clang creates: foo: movzwl 16(%esp), %edx movzwl 12(%esp), %eax addw4(%esp), %ax addw8(%esp), %dx retl So, it is incompatible with itself for -msse/-mno-sse differences. The ABI should be ISA agnostic, so using integer ABI as implemented by gcc is IMO the way to go.
[Bug target/102143] ABI incompatibility with clang when passing 32bit vectors on 32bit i686
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102143 H.J. Lu changed: What|Removed |Added Ever confirmed|0 |1 Last reconfirmed||2021-08-31 Status|UNCONFIRMED |NEW --- Comment #1 from H.J. Lu --- 16-bit and 32-bit vector pass and return are not specified in i386 psABI. 64-bit vector is specified, not really usable. Any suggestions?
