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b6f8c7c452
On x86, some instructions have alternate shorter encodings:
1. When the upper 32 bits of destination registers of
andq $imm31, %r64
testq $imm31, %r64
xorq %r64, %r64
subq %r64, %r64
known to be zero, we can encode them without the REX_W bit:
andl $imm31, %r32
testl $imm31, %r32
xorl %r32, %r32
subl %r32, %r32
This optimization is enabled with -O, -O2 and -Os.
2. Since 0xb0 mov with 32-bit destination registers zero-extends 32-bit
immediate to 64-bit destination register, we can use it to encode 64-bit
mov with 32-bit immediates. This optimization is enabled with -O, -O2
and -Os.
3. Since the upper bits of destination registers of VEX128 and EVEX128
instructions are extended to zero, if all bits of destination registers
of AVX256 or AVX512 instructions are zero, we can use VEX128 or EVEX128
encoding to encode AVX256 or AVX512 instructions. When 2 source
registers are identical, AVX256 and AVX512 andn and xor instructions:
VOP %reg, %reg, %dest_reg
can be encoded with
VOP128 %reg, %reg, %dest_reg
This optimization is enabled with -O2 and -Os.
4. 16-bit, 32-bit and 64-bit register tests with immediate may be
encoded as 8-bit register test with immediate. This optimization is
enabled with -Os.
This patch does:
1. Add {nooptimize} pseudo prefix to disable instruction size
optimization.
2. Add optimize to i386_opcode_modifier to tell assembler that encoding
of an instruction may be optimized.
gas/
PR gas/22871
* NEWS: Mention -O[2|s].
* config/tc-i386.c (_i386_insn): Add no_optimize.
(optimize): New.
(optimize_for_space): Likewise.
(fits_in_imm7): New function.
(fits_in_imm31): Likewise.
(optimize_encoding): Likewise.
(md_assemble): Call optimize_encoding to optimize encoding.
(parse_insn): Handle {nooptimize}.
(md_shortopts): Append "O::".
(md_parse_option): Handle -On.
* doc/c-i386.texi: Document -O0, -O, -O1, -O2 and -Os as well
as {nooptimize}.
* testsuite/gas/cfi/cfi-x86_64.d: Pass -O0 to assembler.
* testsuite/gas/i386/ilp32/cfi/cfi-x86_64.d: Likewise.
* testsuite/gas/i386/i386.exp: Run optimize-1, optimize-2,
optimize-3, x86-64-optimize-1, x86-64-optimize-2,
x86-64-optimize-3 and x86-64-optimize-4.
* testsuite/gas/i386/optimize-1.d: New file.
* testsuite/gas/i386/optimize-1.s: Likewise.
* testsuite/gas/i386/optimize-2.d: Likewise.
* testsuite/gas/i386/optimize-2.s: Likewise.
* testsuite/gas/i386/optimize-3.d: Likewise.
* testsuite/gas/i386/optimize-3.s: Likewise.
* testsuite/gas/i386/x86-64-optimize-1.s: Likewise.
* testsuite/gas/i386/x86-64-optimize-1.d: Likewise.
* testsuite/gas/i386/x86-64-optimize-2.d: Likewise.
* testsuite/gas/i386/x86-64-optimize-2.s: Likewise.
* testsuite/gas/i386/x86-64-optimize-3.d: Likewise.
* testsuite/gas/i386/x86-64-optimize-3.s: Likewise.
* testsuite/gas/i386/x86-64-optimize-4.d: Likewise.
* testsuite/gas/i386/x86-64-optimize-4.s: Likewise.
opcodes/
PR gas/22871
* i386-gen.c (opcode_modifiers): Add Optimize.
* i386-opc.h (Optimize): New enum.
(i386_opcode_modifier): Add optimize.
* i386-opc.tbl: Add "Optimize" to "mov $imm, reg",
"sub reg, reg/mem", "test $imm, acc", "test $imm, reg/mem",
"and $imm, acc", "and $imm, reg/mem", "xor reg, reg/mem",
"movq $imm, reg" and AVX256 and AVX512 versions of vandnps,
vandnpd, vpandn, vpandnd, vpandnq, vxorps, vxorpd, vpxor,
vpxord and vpxorq.
* i386-tbl.h: Regenerated.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.