[Bug c++/42633] hinting gcc that restricted pointer dont alias with members of structs

[torbenh at gmx dot de]

------- Comment #2 from torbenh at gmx dot de  2010-01-06 13:19 -------
 the generated x86_64 asm:  _Z11fill_bufferPfm: .LFB3:  testq   %rsi, %rsi     
je      .L4     xorl    %eax, %eax      movss   .LC0(%rip), %xmm2      
.p2align 4,,10  .p2align 3 .L3:         movss   ramp(%rip), %xmm1       movaps 
%xmm1, %xmm0    addss   %xmm2, %xmm0    movss   %xmm0, ramp(%rip)       movss  
%xmm1, (%rdi,%rax,4)    addq    $1, %rax        cmpq    %rax, %rsi      ja     
.L3 .L4:        rep     ret   while gcc patched with -fnoalias generates:  
_Z11fill_bufferPfm: .LFB1:  .cfi_startproc  .cfi_personality
0x3,__gxx_personality_v0       testq   %rsi, %rsi      je      .L4     movss  
ramp(%rip), %xmm0       xorl    %eax, %eax      movss   .LC0(%rip), %xmm1      
.p2align 4,,10  .p2align 3 .L3:         movss   %xmm0, (%rdi,%rax,4)    addq   
$1, %rax        addss   %xmm1, %xmm0    cmpq    %rax, %rsi      ja      .L3    
movss   %xmm0, ramp(%rip) .L4:  rep     ret 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42633