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digitalmars.D.bugs - [Issue 4034] New: double-double functions seem to not pure-optimize

http://d.puremagic.com/issues/show_bug.cgi?id=4034

           Summary: double-double functions seem to not pure-optimize
           Product: D
           Version: future
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: performance
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2010-03-31 09:45:44 PDT ---
This small D2 program calls two times a function msin that I have tagged as
pure, but in the binary there are two sin instructions, I don't understand:


import std.c.stdio: printf;
import std.c.stdlib: atof;
import std.math: sin;
pure double msin(double x) {
    return sin(x);
}
void main() {
    double x = atof("0.3");
    double y = msin(x) + msin(x);
    printf("%f\n", y);
}


Compiled with dmd v2.042:
dmd -O -release -inline bug1.d

Produces:

_D4bug14msinFNadZd:
        fld qword ptr 4[ESP]
        fsin
        ret 8

__Dmain:
L0:     sub ESP,01Ch
        mov EAX,offset FLAT:_DATA
        push    EAX
        call    near ptr _atof
        mov ECX,offset FLAT:_DATA[4]
        fstp    qword ptr 8[ESP]
        fld qword ptr 8[ESP]
        fsin
        fld qword ptr 8[ESP]
        sub ESP,8
        fsin
        faddp   ST(1),ST
        fstp    qword ptr [ESP]
        push    ECX
        call    near ptr _printf
        add ESP,010h
        add ESP,01Ch
        xor EAX,EAX
        ret


Similar code is produced with this line:
double y = sin(x) + sin(x);

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Mar 31 2010