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Re: [LLVMdev] clang .code16 with -Os producing larger code that it needs


From: David Woodhouse
Subject: Re: [LLVMdev] clang .code16 with -Os producing larger code that it needs to
Date: Mon, 23 Feb 2015 12:07:53 +0000

On Fri, 2015-02-20 at 13:47 -0500, Rafael Espíndola wrote:
> > Your task, should you choose to accept it, is to make it cope with other
> > forms of relaxation where necessary.
> 
> And if not, please open a bug :-)

http://llvm.org/bugs/show_bug.cgi?id=22662

FWIW I could reproduce the 'movl foo, %ebx' one but a relative jump
*was* using 16 bits (although gas uses 8):

 $ cat foo.S
.code16
        jae foo
        movl (foo), %ebx
foo:
 $ gcc -c -oa.out foo.S   ; llvm-objdump -d -triple=i686-pc-linux-code16  

a.out:  file format ELF64-x86-64

Disassembly of section .text:
.text:
       0:       73 05                                           jae     5
       2:       66 8b 1e 00 00                                  movl    0, %ebx
 $ llvm-mc -filetype=obj foo.S | llvm-objdump -d -triple=i686-pc-linux-code16 - 

<stdin>:        file format ELF64-x86-64

Disassembly of section .text:
.text:
       0:       0f 83 08 00                                     jae     8
       4:       67 66 8b 1d 00 00 00 00                         movl    0, %ebx


-- 
dwmw2

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