For R6+, it allows to configure gcc to use compact branches only.
---
gcc/config.gcc | 18 +++++++++++++++++-
gcc/doc/install.texi | 23 +++++++++++++++++++++++
2 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/gcc/config.gcc b/gcc/config.gcc
index 17fea83b2e4..7d50e7995d2 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -4743,7 +4743,7 @@ case "${target}" in
;;
mips*-*-*)
- supported_defaults="abi arch arch_32 arch_64 float fpu nan
fp_32 odd_spreg_32 tune tune_32 tune_64 divide llsc mips-plt synci lxc1-sxc1
madd4"
+ supported_defaults="abi arch arch_32 arch_64 float fpu nan
fp_32 odd_spreg_32 tune tune_32 tune_64 divide llsc mips-plt synci lxc1-sxc1
madd4 compact-branches"
case ${with_float} in
"" | soft | hard)
@@ -4896,6 +4896,22 @@ case "${target}" in
exit 1
;;
esac
+
+ case ${with_compact_branches} in
+ never | always | optimal | prefer)
+ if test "$with_compact_branches" = "always" -a \
+ "$default_mips_arch" != "mips32r6" -a \
+ "$default_mips_arch" != "mips64r6";then
+ echo "Compact-branch=always is not allowed for
pre-R6" 1>&2
+ exit 1
+ fi
+ with_compact_branches=${with_compact_branches}
+ ;;
+ *)
+ echo "Unknown compact-branches policy used in
--with-compact-branches" 1>&2
+ exit 1
+ ;;
+ esac
;;
nds32*-*-*)
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 4c38244ae58..6b9520569ba 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1464,6 +1464,29 @@ systems that support conditional traps).
Division by zero checks use the break instruction.
@end table
+@item --with-compact-branches=@var{policy}
+Specify how the compiler should generate code for checking for
+division by zero. This option is only supported on the MIPS target.
+The possibilities for @var{type} are:
+@table @code
+@item optimal
+Cause a delay slot branch to be used if one is available in the
+current ISA and the delay slot is successfully filled. If the delay slot
+is not filled, a compact branch will be chosen if one is available.
+@item never
+Ensures that compact branch instructions will never be generated.
+@item always
+Ensures that a compact branch instruction will be generated if available.
+If a compact branch instruction is not available,
+a delay slot form of the branch will be used instead.
+This option is supported from MIPS Release 6 onwards.
+@item prefer
+Ensures that a compact branch instruction will be generated if available
+on MIPS Release 6 onwards.
+Simliar with @option{always} besides that this option works for pre-R6
+target, on which, this option will just be ignored.
+@end table
+
@c If you make --with-llsc the default for additional targets,
@c update the --with-llsc description in the MIPS section below.
--
2.20.1
