• d-bugmail puremagic.com (42/42) Jul 19 2011 http://d.puremagic.com/issues/show_bug.cgi?id=6350

d-bugmail puremagic.com writes:

http://d.puremagic.com/issues/show_bug.cgi?id=6350

           Summary: Const array static usage optimization
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: Windows
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



A D2 program:


enum int[1] array1 = [10];
int foo(int[1] v) {
    return array1[0] * v[0];
}
const int[1] array2 = [10];
int bar(int[1] v) {
    return array2[0] * v[0];
}
void main() {}


The asm of the two functions (dmd 2.054, -O -release), inside bar() the
contents of array2 are loaded with a mov instruction:

_D4test3fooFG1iZi   comdat
        push    EAX
        lea EAX,[EAX*4][EAX]
        add EAX,EAX
        pop ECX
        ret

_D4test3barFG1iZi   comdat
        push    EAX
        mov EAX,_D4test6array2xG1i
        imul    EAX,[ESP]
        pop ECX
        ret


Is it possible for the compiler for such common case of const array to remove
the mov instruction from the bar () function too?

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