https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98694
--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
cprop hardreg change
(insn 457 499 460 33 (set (reg:SI 39 r11 [orig:86 _11 ] [86])
(reg:SI 37 r9 [orig:86 _11 ] [86])) "test.c":29:36 75 {*movsi_internal}
(expr_list:REG_DEAD (reg:SI 37 r9 [orig:86 _11 ] [86])
(nil)))
to
(insn 457 499 460 33 (set (reg:SI 39 r11 [orig:86 _11 ] [86])
(reg:SI 22 xmm2 [orig:86 _11 ] [86])) "test.c":29:36 75
{*movsi_internal}
(expr_list:REG_DEAD (reg:SI 22 xmm2 [orig:86 _11 ] [86])
(nil)))
since it thought the lower 32bit of r9 and xmm2 is the same?
but with xmm2 defined as
kmovw %k0, %edi # 69 [c=4 l=4] *movhi_internal/6
kmovd %k0, %edx # 487 [c=4 l=3] *movsi_internal/16
vmovd %edi, %xmm2 # 489
the bit16-32 is clear with kmovw(note k0 is equal to r9 with SImode, it's var_6
in source code)
(insn 69 68 70 12 (set (reg:HI 5 di [orig:96 _52 ] [96])
(reg:HI 68 k0 [orig:82 var_6.0_1 ] [82])) "test.c":21:23 76
{*movhi_internal}
(nil))
(insn 489 75 78 12 (set (reg:SI 22 xmm2 [297])
(reg:SI 5 di [orig:96 _52 ] [96])) 75 {*movsi_internal}
(nil))
