<HTML><HEAD><TITLE>Samsung Enterprise Portal mySingle</TITLE>
<META content=IE=5 http-equiv=X-UA-Compatible>
<META content="text/html; charset=utf-8" http-equiv=Content-Type>
<STYLE id=mysingle_style type=text/css>P {
MARGIN-BOTTOM: 5px; FONT-SIZE: 9pt; FONT-FAMILY: Arial, arial; MARGIN-TOP: 5px
}
TD {
MARGIN-BOTTOM: 5px; FONT-SIZE: 9pt; FONT-FAMILY: Arial, arial; MARGIN-TOP: 5px
}
LI {
MARGIN-BOTTOM: 5px; FONT-SIZE: 9pt; FONT-FAMILY: Arial, arial; MARGIN-TOP: 5px
}
BODY {
FONT-SIZE: 9pt; FONT-FAMILY: Arial, arial; MARGIN: 10px; LINE-HEIGHT: 1.4
}
</STYLE>
<META name=GENERATOR content=ActiveSquare></HEAD>
<BODY>
<META name=GENERATOR content=ActiveSquare>
<P>Hi Jonathan,</P>
<P>The assembly generated in case of clang-3.5 is</P>
<P>indirect_call:<BR> .fnstart<BR>.Leh_func_begin0:<BR> ldr r0, .LCPI0_0<BR> ldr r1, .LCPI0_1<BR>.LPC0_0:<BR> add r0, pc, r0<BR> ldr r0, [r1, r0]<BR> ldr r0, [r0]<BR> bx r0<BR> .align 2<BR>.LCPI0_0:<BR> .long _GLOBAL_OFFSET_TABLE_-(.LPC0_0+8)<BR>.LCPI0_1:<BR> .long indirect_func(GOT)<BR>.Ltmp0:<BR> .size indirect_call, .Ltmp0-indirect_call<BR>.Leh_func_end0:<BR> .fnend</P>
<P> </P>
<P>with clang-3.4.2 the assembly generated is:</P>
<P>ndirect_call:<BR> push {r11, lr}<BR> ldr r0, .LCPI0_0<BR> mov r11, sp<BR> ldr r1, .LCPI0_1<BR>.LPC0_0:<BR> add r0, pc, r0<BR> ldr r0, [r1, r0]<BR> ldr r0, [r0]<BR> blx r0<BR> pop {r11, pc}<BR> .align 2<BR>.LCPI0_0:<BR> .long _GLOBAL_OFFSET_TABLE_-(.LPC0_0+8)<BR>.LCPI0_1:<BR> .long indirect_func(GOT)<BR>.Ltmp0:<BR> .size indirect_call, .Ltmp0-indirect_call</P>
<P> </P>
<P>Both assemblies are generated with O1 optimization. The assembly generated with trunk version of clang is similar to 3.5</P>
<P> </P>
<P>Thanks,</P>
<P>Mayur</P>
<P> </P>
<P>------- <B>Original Message</B> -------</P>
<P><B>Sender</B> : Jonathan Roelofs<jonathan@codesourcery.com></P>
<P><B>Date</B> : Nov 25, 2014 10:15 (GMT+09:00)</P>
<P><B>Title</B> : Re: [LLVMdev] bx instruction getting generated in arm assembly for O1</P>
<P> </P><BR><BR>On 11/24/14 8:00 AM, MAYUR PANDEY wrote:<BR>> Hi,<BR>><BR>> For the following test:<BR>><BR>> int (*indirect_func)();<BR>><BR>> int indirect_call()<BR>> {<BR>> return indirect_func();<BR>> }<BR>><BR>> when generating the assembly with clang-3.5, for -march=armv5te, there is a<BR>> difference in the assemblies generated with O0 and O1:<BR>><BR>> In the assembly generated with O0, we are getting the "blx" instruction whereas<BR>> with O1 we get "bx" (in 3.4.2 we used to get "blx" for both O0 and O1).<BR>Can you post the asm that you're seeing for this function?<BR><BR>There's a related case to this on armv4t which Iain has a patch for, that I <BR>think we forgot about... The problem there is that armv4t doesn't have blx at <BR>all, so should be generating a sequence like: 'mov r0, ...; bx _Ltmp; _Ltmp: bl r0'.<BR>><BR>> Is this because of this patch: [llvm] r214959 - ARM: do not generate BLX<BR>> instructions on Cortex-M CPUs<BR>I doubt it. armv5te isn't a cortex-m processor.<BR><BR><BR>Cheers,<BR><BR>Jon<BR>><BR>> Or I am missing something.<BR>><BR>> Thanks,<BR>><BR>> Mayur<BR>><BR>><BR>><BR>><BR>> _______________________________________________<BR>> LLVM Developers mailing list<BR>> LLVMdev@cs.uiuc.edu http://llvm.cs.uiuc.edu<BR>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev<BR>><BR><BR>-- <BR>Jon Roelofs<BR>jonathan@codesourcery.com<BR>CodeSourcery / Mentor Embedded<BR>
<P> </P><!--SP:mayur.p--><!--mayur.p:EP-->
<P> </P></BODY></HTML><img src='http://ext.samsung.net/mailcheck/SeenTimeChecker?do=e3e1a57eba32dd3d2f058a73fc979ba602f9d56712beed49f294c62af3385af4958dbbabe087ac9c0029dc535ebebcd3326bbdfb2ea96a2fcf878f9a26ce15a0' border=0 width=0 height=0 style='display:none'>