On Mon, Oct 3, 2011 at 5:53 PM, H.J. Lu <hjl.tools@xxxxxxxxx> wrote: > On Mon, Oct 3, 2011 at 4:47 PM, Michael LIAO <michael.hliao@xxxxxxxxx> wrote: >> On Mon, Oct 3, 2011 at 4:03 PM, Mike Frysinger <vapier@xxxxxxxxxx> wrote: >>> On Monday, October 03, 2011 18:57:28 Michael LIAO wrote: >>> >>> please don't top post >>> >> >> sorry, it's my first post on mailing. >> >>>> Most examples would be related to tools generating code. >>>> >>>> Suppose you have a software package with several hard-coded fully >>>> optimized assembly file for different targets. Your build system need >>>> to know the current target as well as target ABI to select the correct >>>> assembly file to build it. It even desirable if it includes a simple >>>> script to help generate assembly code (like the one in OpenSSL), you'd >>>> better know the target ABI to prepare proper glue code without >>>> breaking ABI. >>> >>> hjlu posted examples to the x32 site as to handle this. the only difference >>> between x86_64 and x32 is the size of the pointers. >>> >> >> Besides the pointer size, there are other differences like indirect >> branch which need different code sequence on x32 and x64. Indirect >> branch would be used in assembly code (yeah, concrete example would >> valuable here but indirect branch should be used potentially and >> possibly in assembly code.) If the assembly code use indirect branch, >> it needs to know the target ABI and generate/use difference code path. >> > > In assembly codes, most, if not all, of x86-64 indirect branch work fine for x32 > that may cause the target IP out of the first 4G range if assembly code won't follow x32 abi, e.g. indirect target is stored in a memory location and assembly direct use 64-bit near absolute indirect call with m64 opernad since the branch target is 32 bits in memory but that call will read 64-bit value and result in garbage on high 32 bits of the final IP. > > -- > H.J. > _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx https://lists.gnu.org/mailman/listinfo/autoconf
