https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89229
--- Comment #19 from H.J. Lu <hjl.tools at gmail dot com> ---
sse.md has
(define_insn "mov<mode>_internal"
[(set (match_operand:VMOVE 0 "nonimmediate_operand"
"=v,v ,v ,m")
(match_operand:VMOVE 1 "nonimmediate_or_sse_const_operand"
" C,BC,vm,v"))]
....
/* There is no evex-encoded vmov* for sizes smaller than 64-bytes
in avx512f, so we need to use workarounds, to access sse registers
16-31, which are evex-only. In avx512vl we don't need workarounds. */
if (TARGET_AVX512F && <MODE_SIZE> < 64 && !TARGET_AVX512VL
&& (EXT_REX_SSE_REG_P (operands[0])
|| EXT_REX_SSE_REG_P (operands[1])))
{
if (memory_operand (operands[0], <MODE>mode))
{
if (<MODE_SIZE> == 32)
return "vextract<shuffletype>64x4\t{$0x0, %g1, %0|%0, %g1,
0x0}";
else if (<MODE_SIZE> == 16)
return "vextract<shuffletype>32x4\t{$0x0, %g1, %0|%0, %g1,
0x0}";
else
gcc_unreachable ();
}
...
However, ix86_hard_regno_mode_ok has
/* TODO check for QI/HI scalars. */
/* AVX512VL allows sse regs16+ for 128/256 bit modes. */
if (TARGET_AVX512VL
&& (mode == OImode
|| mode == TImode
|| VALID_AVX256_REG_MODE (mode)
|| VALID_AVX512VL_128_REG_MODE (mode)))
return true;
/* xmm16-xmm31 are only available for AVX-512. */
if (EXT_REX_SSE_REGNO_P (regno))
return false;
if (TARGET_AVX512F && <MODE_SIZE> < 64 && !TARGET_AVX512VL
&& (EXT_REX_SSE_REG_P (operands[0])
|| EXT_REX_SSE_REG_P (operands[1])))
is a dead code:
[hjl@gnu-4 gcc]$ cat /tmp/z.c
#include <immintrin.h>
extern __m128 i;
__m128
foo1 (void)
{
register __m128 xmm16 __asm ("xmm16") = i;
asm volatile ("" : "+v" (xmm16));
register __m128 xmm17 __asm ("xmm17") = xmm16;
asm volatile ("" : "+v" (xmm17));
return xmm17;
}
[hjl@gnu-4 gcc]$ /usr/gcc-5.4.1-x32/bin/gcc -S -O2 -march=knl /tmp/z.c
/tmp/z.c: In function ‘foo1’:
/tmp/z.c:8:19: error: register specified for ‘xmm16’ isn’t suitable for data
type
register __m128 xmm16 __asm ("xmm16") = i;
^
/tmp/z.c:10:19: error: register specified for ‘xmm17’ isn’t suitable for data
type
register __m128 xmm17 __asm ("xmm17") = xmm16;
^
[hjl@gnu-4 gcc]$
