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digitalmars.D - -inline makes executable smaller!

reply "Kris" <fu bar.com> writes:
I know; that sounds like a headline from BBSpot. Still, -inline actually 
shrank an exec by half a K. All that call overhead is killing us :-)

Classic headline: http://www.bbspot.com/News/2000/5/clock_rift.html 
Dec 06 2005
parent reply "Walter Bright" <newshound digitalmars.com> writes:
"Kris" <fu bar.com> wrote in message news:dn5aih$1fq$1 digitaldaemon.com...
 I know; that sounds like a headline from BBSpot. Still, -inline actually
 shrank an exec by half a K. All that call overhead is killing us :-)

Many inline functions have smaller code generated for them than they require in stack frame setup/teardown code. Also, inlining enables better register allocation.
Dec 06 2005
next sibling parent James Dunne <james.jdunne gmail.com> writes:
Walter Bright wrote:
 "Kris" <fu bar.com> wrote in message news:dn5aih$1fq$1 digitaldaemon.com...
 
I know; that sounds like a headline from BBSpot. Still, -inline actually
shrank an exec by half a K. All that call overhead is killing us :-)

Many inline functions have smaller code generated for them than they require in stack frame setup/teardown code. Also, inlining enables better register allocation.

Not to mention the possible pipelining benefits on modern processors and the possible preservation of locality of reference (not destroying the cache)
Dec 06 2005
prev sibling parent reply Fredrik Olsson <peylow treyst.se> writes:
Walter Bright skrev:
 "Kris" <fu bar.com> wrote in message news:dn5aih$1fq$1 digitaldaemon.com...
 I know; that sounds like a headline from BBSpot. Still, -inline actually
 shrank an exec by half a K. All that call overhead is killing us :-)

Many inline functions have smaller code generated for them than they require in stack frame setup/teardown code. Also, inlining enables better register allocation.

inlining, on what premises is this actually done? I guess you Walter does not have the answer, but is this also done with GDC in some special way or is it left to normal GCC behavior (enabled by -finline-functions and -O3)? // Fredrik Olsson
Dec 07 2005
parent James Dunne <james.jdunne gmail.com> writes:
Fredrik Olsson wrote:
 Walter Bright skrev:
 
 "Kris" <fu bar.com> wrote in message 
 news:dn5aih$1fq$1 digitaldaemon.com...

 I know; that sounds like a headline from BBSpot. Still, -inline actually
 shrank an exec by half a K. All that call overhead is killing us :-)

Many inline functions have smaller code generated for them than they require in stack frame setup/teardown code. Also, inlining enables better register allocation.

inlining, on what premises is this actually done? I guess you Walter does not have the answer, but is this also done with GDC in some special way or is it left to normal GCC behavior (enabled by -finline-functions and -O3)? // Fredrik Olsson

I would assume the language SPEC makes no assumptions as to the implementation of inlining choosing. But if you're curious as to how the reference implementation chooses, you can look at the DMD front-end's source code. I'd recommend starting at dmd/src/dmd/inline.c and going from there. On a quick glance it seems to be estimating costs per operation and totalling them up for the function in question. If the total cost is less than some threshold, then the function can be inlined, otherwise it's assumed to be not worth the inlining effort. This is a good, general, heuristic approach to things and should work for most cases.
Dec 07 2005