[Bug target/48678] unable to find a register to spill in class ‘GENERAL_REGS’

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48678

--- Comment #12 from Uros Bizjak <ubizjak at gmail dot com> 2011-04-20 14:27:30 UTC ---
Hm, if line 14 in the testcase is changed to:

-  ((T *) &s.d)[0] = *x;
+  ((T *) &s.d)[1] = *x;

then gcc does not touch movstrict pattern at all and generates following code:

    movdqa    (%rsi), %xmm0
    movabsq    $-4294901761, %rsi
    movzwl    (%rdi), %eax
    movdqa    %xmm0, -24(%rsp)
    movq    -24(%rsp), %rcx
    salq    $16, %rax
    andq    %rsi, %rcx
    orq    %rax, %rcx
    movq    %rcx, -24(%rsp)
    movdqa    -24(%rsp), %xmm0
    pcmpeqw    (%rdx), %xmm0
    ret

However, when byte offset reaches sizeof (*void), i.e. 8 bytes on 64bit target
as in:

-  ((T *) &s.d)[0] = *x;
+  ((T *) &s.d)[4] = *x;

then we again get:

    movdqa    (%rsi), %xmm0
    pinsrw    $4, (%rdi), %xmm0
    pcmpeqw    (%rdx), %xmm0
    ret

I didn't investigate this in detail, but perhaps someone can shed some light
here?