463d910876
C++20:
#include <compare>
auto cmp4way(double a, double b)
{
return a <=> b;
}
expands to:
ucomisd %xmm1, %xmm0
jp .L8
movl $0, %eax
jne .L8
.L2:
ret
.p2align 4,,10
.p2align 3
.L8:
comisd %xmm0, %xmm1
movl $-1, %eax
ja .L2
ucomisd %xmm1, %xmm0
setbe %al
addl $1, %eax
ret
That is 3 comparisons of the same operands.
The following patch improves it to just one comparison:
comisd %xmm1, %xmm0
jp .L4
seta %al
movl $0, %edx
leal -1(%rax,%rax), %eax
cmove %edx, %eax
ret
.L4:
movl $2, %eax
ret
While a <=> b expands to a == b ? 0 : a < b ? -1 : a > b ? 1 : 2
where the first comparison is equality and this shouldn't raise
exceptions on qNaN operands, if the operands aren't equal (which
includes unordered cases), then it immediately performs < or >
comparison and that raises exceptions even on qNaNs, so we can just
perform a single comparison that raises exceptions on qNaN.
As the 4 different cases are encoded as
ZF CF PF
1 1 1 a unordered b
0 0 0 a > b
0 1 0 a < b
1 0 0 a == b
we can emit optimal sequence of comparions, first jp
for the unordered case, then je for the == case and finally jb
for the < case.
The patch pattern recognizes spaceship-like comparisons during
widening_mul if the spaceship optab is implemented, and replaces
those comparisons with comparisons of .SPACESHIP ifn which returns
-1/0/1/2 based on the comparison. This seems to work well both for the
case of just returning the -1/0/1/2 (when we have just a common
successor with a PHI) or when the different cases are handled with
various other basic blocks. The testcases cover both of those cases,
the latter with different function calls in those.
2022-01-17 Jakub Jelinek <jakub@redhat.com>
PR target/103973
* tree-cfg.h (cond_only_block_p): Declare.
* tree-ssa-phiopt.c (cond_only_block_p): Move function to ...
* tree-cfg.c (cond_only_block_p): ... here. No longer static.
* optabs.def (spaceship_optab): New optab.
* internal-fn.def (SPACESHIP): New internal function.
* internal-fn.h (expand_SPACESHIP): Declare.
* internal-fn.c (expand_PHI): Formatting fix.
(expand_SPACESHIP): New function.
* tree-ssa-math-opts.c (optimize_spaceship): New function.
(math_opts_dom_walker::after_dom_children): Use it.
* config/i386/i386.md (spaceship<mode>3): New define_expand.
* config/i386/i386-protos.h (ix86_expand_fp_spaceship): Declare.
* config/i386/i386-expand.c (ix86_expand_fp_spaceship): New function.
* doc/md.texi (spaceship@var{m}3): Document.
* gcc.target/i386/pr103973-1.c: New test.
* gcc.target/i386/pr103973-2.c: New test.
* gcc.target/i386/pr103973-3.c: New test.
* gcc.target/i386/pr103973-4.c: New test.
* gcc.target/i386/pr103973-5.c: New test.
* gcc.target/i386/pr103973-6.c: New test.
* gcc.target/i386/pr103973-7.c: New test.
* gcc.target/i386/pr103973-8.c: New test.
* gcc.target/i386/pr103973-9.c: New test.
* gcc.target/i386/pr103973-10.c: New test.
* gcc.target/i386/pr103973-11.c: New test.
* gcc.target/i386/pr103973-12.c: New test.
* gcc.target/i386/pr103973-13.c: New test.
* gcc.target/i386/pr103973-14.c: New test.
* gcc.target/i386/pr103973-15.c: New test.
* gcc.target/i386/pr103973-16.c: New test.
* gcc.target/i386/pr103973-17.c: New test.
* gcc.target/i386/pr103973-18.c: New test.
* gcc.target/i386/pr103973-19.c: New test.
* gcc.target/i386/pr103973-20.c: New test.
* g++.target/i386/pr103973-1.C: New test.
* g++.target/i386/pr103973-2.C: New test.
* g++.target/i386/pr103973-3.C: New test.
* g++.target/i386/pr103973-4.C: New test.
* g++.target/i386/pr103973-5.C: New test.
* g++.target/i386/pr103973-6.C: New test.
* g++.target/i386/pr103973-7.C: New test.
* g++.target/i386/pr103973-8.C: New test.
* g++.target/i386/pr103973-9.C: New test.
* g++.target/i386/pr103973-10.C: New test.
* g++.target/i386/pr103973-11.C: New test.
* g++.target/i386/pr103973-12.C: New test.
* g++.target/i386/pr103973-13.C: New test.
* g++.target/i386/pr103973-14.C: New test.
* g++.target/i386/pr103973-15.C: New test.
* g++.target/i386/pr103973-16.C: New test.
* g++.target/i386/pr103973-17.C: New test.
* g++.target/i386/pr103973-18.C: New test.
* g++.target/i386/pr103973-19.C: New test.
* g++.target/i386/pr103973-20.C: New test.
|
||
|---|---|---|
| c++tools | ||
| config | ||
| contrib | ||
| fixincludes | ||
| gcc | ||
| gnattools | ||
| gotools | ||
| include | ||
| INSTALL | ||
| intl | ||
| libada | ||
| libatomic | ||
| libbacktrace | ||
| libcc1 | ||
| libcody | ||
| libcpp | ||
| libdecnumber | ||
| libffi | ||
| libgcc | ||
| libgfortran | ||
| libgo | ||
| libgomp | ||
| libiberty | ||
| libitm | ||
| libobjc | ||
| liboffloadmic | ||
| libphobos | ||
| libquadmath | ||
| libsanitizer | ||
| libssp | ||
| libstdc++-v3 | ||
| libvtv | ||
| lto-plugin | ||
| maintainer-scripts | ||
| zlib | ||
| .dir-locals.el | ||
| .gitattributes | ||
| .gitignore | ||
| ABOUT-NLS | ||
| ar-lib | ||
| build.log | ||
| ChangeLog | ||
| ChangeLog.jit | ||
| ChangeLog.tree-ssa | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LIB | ||
| COPYING.RUNTIME | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| depcomp | ||
| install-sh | ||
| libtool-ldflags | ||
| libtool.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| lt~obsolete.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| multilib.am | ||
| README | ||
| symlink-tree | ||
| test-driver | ||
| ylwrap | ||
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.