Thorsten Ottosen wrote:
Michael Marcin skrev:
Hi,
I have a problem with my compiler (ARM's RVCT 2.2.1). It is not generating optimal code for ptr_containers, specifically I've been looking at ptr_vector. I love using ptr_containers to convery ownership but I rely on them being zero overhead over std::vector with explicit delete loops for at least simple operations like a for each loop.
I would hope these 2 files (attached) would generate identical assembly for the foo function but they are not even close (attached as txt).
I know there are a lot of compilers that are a lot smarter than this one. Unfortunately I'm stuck with this one so I need to teach this compiler to generate better code (by modifying the ptr_container library) or stop using ptr_containers (cry).
Hi Michael,
Some compilers have a problem doing near-perfect inlining, which can be a real killer.
I'll try to investigate this.
I appreciate it. If you have things you'd like me to try out I can compile them and send you the mixed assembly output. One thing I noticed is that it seems to fail to eliminate the return value copy of the void_ptr_iterator::base call. Accessing iter_ directly (unfortunately) produces much better code but still not the best. _Z3foov PROC ; foo() ;;;14 void foo() ;;;15 { 000000 490d LDR r1,|L1.56| 000002 b50c PUSH {r2,r3,lr} 000004 6848 LDR r0,[r1,#4] 000006 9001 STR r0,[sp,#4] ;181 000008 6808 LDR r0,[r1,#0] 00000a e005 B |L1.24| |L1.12| 00000c 6800 LDR r0,[r0,#0] 00000e 6801 LDR r1,[r0,#0] 000010 1c49 ADDS r1,r1,#1 000012 6001 STR r1,[r0,#0] 000014 9800 LDR r0,[sp,#0] 000016 1d00 ADDS r0,r0,#4 |L1.24| 000018 9901 LDR r1,[sp,#4] 00001a 9000 STR r0,[sp,#0] 00001c 4288 CMP r0,r1 00001e d1f5 BNE |L1.12| 000020 bd0c POP {r2,r3,pc} ;186 ;;;16 boost::ptr_vector<b>::iterator iend = x.end(); ;;;17 for( boost::ptr_vector<b>::iterator it = x.begin(); it != iend; ++it ) ;;;18 { ;;;19 b& b_ = *it; ;;;20 b_.bar(); ;;;21 } ;;;22 } ENDP Thanks, Michael Marcin