Switch to list all druntime calls?

[bearophile via Digitalmars-d]

This shows one purpose of the ldc2 -noruntime switch. A simple 
test program:


void foo(ref int[10] data) {
     data[0 .. 3] = 5;
     data[7 .. 9] = 10;
}
void main() {}


dmd compiles it to:

_D5test53fooFKG10iZv:
L0:     push    EAX
         push    3
         push    5
         push    EAX
         call    near ptr __memset32
         push    2
         push    0Ah
         mov EAX,014h[ESP]
         lea ECX,01Ch[EAX]
         push    ECX
         call    near ptr __memset32
         add ESP,018h
         pop EAX
         ret


ldc2 is smarter and removes the calls to memset, generating kind 
of optimal 32 bit code:

__D5test53fooFKG10iZv:
     movl    $5, (%eax)
     movl    $5, 4(%eax)
     movl    $5, 8(%eax)
     movl    $10, 28(%eax)
     movl    $10, 32(%eax)
     ret

If you call such function many times you see a significant run 
time difference between the two compilations.

A switch like -noruntime helps find the unwanted cases where the 
compiler you are using doesn't remove some run time call.

Bye,
bearophile