[PATCH, i386]: Fix PR 36079 [4.3/4.4 Regression] cld instruction is not emitted anymore.

["Uros Bizjak" <ubizjak at gmail dot com>]

Hello!

OK, here is the controversial patch that enables cld instruction with
-mcld. It includes --enable-cld configure option, and in this case
-mno-cld disables generation of cld instructions.

2008-05-20  Uros Bizjak  <ubizjak@gmail.com>

        PR target/36079
        * configure.ac: Handle --enable-cld.
        * configure.in: Regenerate.
        * configure.ac: Ditto.
        * config/i386/i386.h (TARGET_CLD): New define.
        (struct machine_function): Add needs_cld field.
        (ix86_current_function_needs_cld): New define.
        * config/i386/i386.md (UNSPEC_CLD): New unspec volatile constant.
        ("cld"): New isns pattern.
        ("strmov_singleop"): Set ix86_current_function_needs_cld flag.
        ("rep_mov"): Ditto.
        ("strset_singleop"): Ditto.
        ("rep_stos"): Ditto.
        ("cmpstrnqi_nz_1"): Ditto.
        ("cmpstrnqi_1"): Ditto.
        ("strlenqi_1"): Ditto.
        * config/i386/i386.opt (mcld, mno-cld): New options.
        * config/i386/i386.c (ix86_expand_prologue): Emit cld insn for
        when ix86_current_function_needs_cld is set and when combination
        of configure and compile options allow it.

The patch was bootstrapped and regression tested on i686-pc-linux-gnu
a month or so ago. Currently vanila (without patch!) gcc-4_3 branch
doesn't build for me, it dies with:

gcc -c   -g -fkeep-inline-functions -DIN_GCC   -W -Wall
-Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes
-Wold-style-definition -Wmissing-format-attribute -pedantic
-Wno-long-long -Wno-variadic-macros      -Wno-overlength-strings
-fno-common   -DHAVE_CONFIG_H -DGENERATOR_FILE -I. -Ibuild
-I../../gcc-svn/branches/gcc-4_3-branch/gcc
-I../../gcc-svn/branches/gcc-4_3-branch/gcc/build
-I../../gcc-svn/branches/gcc-4_3-branch/gcc/../include
-I../../gcc-svn/branches/gcc-4_3-branch/gcc/../libcpp/include
-I/usr/local/include
-I../../gcc-svn/branches/gcc-4_3-branch/gcc/../libdecnumber
-I../../gcc-svn/branches/gcc-4_3-branch/gcc/../libdecnumber/bid
-I../libdecnumber    -o build/errors.o
../../gcc-svn/branches/gcc-4_3-branch/gcc/errors.c
build/genmodes -h > tmp-modes.h
/bin/sh: build/genmodes: No such file or directory
gmake[3]: *** [s-modes-h] Error 127

Uros.

Attachment: cld.diff.txt
Description: Text document