Re: gcc -S vs clang -S

2015-05-13 Thread Jakub Jelinek
On Wed, May 13, 2015 at 08:41:39AM -0600, Martin Sebor wrote: On 05/12/2015 07:40 PM, Andrew Pinski wrote: On Tue, May 12, 2015 at 6:36 PM, Fei Ding fding...@gmail.com wrote: I think Thiago and Eric just want to know which code-gen is better and why... You need to understand for a

Re: gcc -S vs clang -S

2015-05-13 Thread Martin Sebor
On 05/12/2015 07:40 PM, Andrew Pinski wrote: On Tue, May 12, 2015 at 6:36 PM, Fei Ding fding...@gmail.com wrote: I think Thiago and Eric just want to know which code-gen is better and why... You need to understand for a complex process (CISC ISAs) like x86, there is no one right answer

Re: gcc -S vs clang -S

2015-05-12 Thread Andrew Pinski
On Tue, May 12, 2015 at 6:36 PM, Fei Ding fding...@gmail.com wrote: I think Thiago and Eric just want to know which code-gen is better and why... You need to understand for a complex process (CISC ISAs) like x86, there is no one right answer sometimes. You need to look at each micro-arch and

Re: gcc -S vs clang -S

2015-05-12 Thread Fei Ding
I think Thiago and Eric just want to know which code-gen is better and why... 2015-05-12 23:29 GMT+08:00 Eric Botcazou ebotca...@libertysurf.fr: Note that at -O3 there is a difference still: clang (3.6.0): addl%esi, %edi movl%edi, %eax retq gcc (4.9.2)

Re: gcc -S vs clang -S

2015-05-12 Thread Olivier Galibert
Note that at -O3 there is a difference still: clang (3.6.0): addl%esi, %edi movl%edi, %eax retq gcc (4.9.2) leal(%rdi,%rsi), %eax ret Can't tell which is best, if any. OG. On Tue, May 12, 2015 at 4:06 AM, pins...@gmail.com wrote: On

Re: gcc -S vs clang -S

2015-05-12 Thread Eric Botcazou
Note that at -O3 there is a difference still: clang (3.6.0): addl%esi, %edi movl%edi, %eax retq gcc (4.9.2) leal(%rdi,%rsi), %eax ret Can't tell which is best, if any. But what's your point exactly here? You cannot expect different

gcc -S vs clang -S

2015-05-11 Thread Thiago Farina
Hi, Clang 3.7 generated the following code: $ clang -S -O0 -fno-unwind-tables -fno-asynchronous-unwind-tables add.c -o add_att_x64.s add: pushq %rbp movq%rsp, %rbp movl%edi, -4(%rbp) movl%esi, -8(%rbp) movl-4(%rbp), %esi

Re: gcc -S vs clang -S

2015-05-11 Thread pinskia
On May 11, 2015, at 6:16 PM, Thiago Farina tfrans...@gmail.com wrote: Hi, Clang 3.7 generated the following code: $ clang -S -O0 -fno-unwind-tables -fno-asynchronous-unwind-tables add.c -o add_att_x64.s add: pushq %rbp movq%rsp, %rbp movl%edi,