[LLVMbugs] [Bug 13204] New: Optimization pass to combine sin, cos library calls to sincos

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13204

             Bug #: 13204
           Summary: Optimization pass to combine sin, cos library calls to
                    sincos
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Transformation Utilities
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: drewm1980 at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


On gcc, when calls to both sin() and cos() math library calls are present, the
get optimized to a single call to sincos().

Here is a newsgroup thread with a small benchmark:
http://lists.cs.uiuc.edu/pipermail/llvmdev/2011-September/043234.html

I checked a quick code snippet:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char **argv) {
float x = *(float*) argv[0]; 
return (int) sinf(x) + cosf(x) + sinf(x) + cosf(x);
}

in the online demo, and this still seems to be the case in clang 3:

.Ltmp2:
    .cfi_def_cfa_offset 16
    movq    (%rsi), %rax
    movss    (%rax), %xmm0
    movss    %xmm0, (%rsp)           # 4-byte Spill
    callq    cosf
    movss    %xmm0, 4(%rsp)          # 4-byte Spill
    movss    (%rsp), %xmm0           # 4-byte Reload
    callq    sinf
    cvttss2si    %xmm0, %eax
    cvtsi2ss    %eax, %xmm1
    movss    4(%rsp), %xmm2          # 4-byte Reload
    addss    %xmm2, %xmm1
    addss    %xmm0, %xmm1
    addss    %xmm2, %xmm1
    cvttss2si    %xmm1, %eax
    popq    %rdx
    ret

Adding support for sincos, sincosf, sincosl might boost performance of
trig-heavy numerical codes, i.e. codes involving a lot of coordinate
transformations, i.e. dynamic equations for robotic systems.  

Apologies in advance if I'm submitting this to the wrong component; I'm very
much just an end user.  Thanks!

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.