mirror of
git://gcc.gnu.org/git/gcc.git
synced 2025-03-21 15:50:55 +08:00
1bd3a8af85
The attached patch eliminates a redundant zero extend from the AArch64 backend. Given the following C code:
unsigned long long foo(unsigned a)
{
return ~a;
}
prior to this patch, AArch64 GCC at -O2 generates:
foo:
mvn w0, w0
uxtw x0, w0
ret
but the uxtw is redundant, since the mvn clears the upper half of the x0 register. After applying this patch, GCC at -O2 gives:
foo:
mvn w0, w0
ret
Testing:
Added regression test which passes after applying the change to aarch64.md.
Full bootstrap and regression on aarch64-linux with no additional failures.
* config/aarch64/aarch64.md (*one_cmpl_zero_extend): New.
* gcc.target/aarch64/mvn_zero_ext.c: New test.
This directory contains the GNU Compiler Collection (GCC). The GNU Compiler Collection is free software. See the files whose names start with COPYING for copying permission. The manuals, and some of the runtime libraries, are under different terms; see the individual source files for details. The directory INSTALL contains copies of the installation information as HTML and plain text. The source of this information is gcc/doc/install.texi. The installation information includes details of what is included in the GCC sources and what files GCC installs. See the file gcc/doc/gcc.texi (together with other files that it includes) for usage and porting information. An online readable version of the manual is in the files gcc/doc/gcc.info*. See http://gcc.gnu.org/bugs/ for how to report bugs usefully. Copyright years on GCC source files may be listed using range notation, e.g., 1987-2012, indicating that every year in the range, inclusive, is a copyrightable year that could otherwise be listed individually.