Re: [PATCH 6/8] AArch64: recognize `+cmpbr` option

[Karl Meakin]

On 07/05/2025 12:48, Kyrylo Tkachov wrote:

On 7 May 2025, at 12:27, Karl Meakin <karl.mea...@arm.com> wrote:

Add the `+cmpbr` option to enable the FEAT_CMPBR architectural
extension.

gcc/ChangeLog:

* config/aarch64/aarch64-option-extensions.def (cmpbr): new
option.
* config/aarch64/aarch64.h (TARGET_CMPBR): new macro.
* doc/invoke.texi (cmpbr): new option.
Looks ok to me.
Not a blocker here, but does this need any FMV handling? I guess this is one of 
those transparent codegen features and maybe doesn’t need FMV clones…
Thanks,
Kyrill

I don't think it needs any special handling, as you say it should be 
handled transparently.
---
gcc/config/aarch64/aarch64-option-extensions.def | 2 ++
gcc/config/aarch64/aarch64.h                     | 3 +++
gcc/doc/invoke.texi                              | 3 +++
3 files changed, 8 insertions(+)

diff --git a/gcc/config/aarch64/aarch64-option-extensions.def 
b/gcc/config/aarch64/aarch64-option-extensions.def
index dbbb021f05a..1c3e69799f5 100644
--- a/gcc/config/aarch64/aarch64-option-extensions.def
+++ b/gcc/config/aarch64/aarch64-option-extensions.def
@@ -249,6 +249,8 @@ AARCH64_OPT_EXTENSION("mops", MOPS, (), (), (), "mops")

AARCH64_OPT_EXTENSION("cssc", CSSC, (), (), (), "cssc")

+AARCH64_OPT_EXTENSION("cmpbr", CMPBR, (), (), (), "cmpbr")
+
AARCH64_OPT_EXTENSION("lse128", LSE128, (LSE), (), (), "lse128")

AARCH64_OPT_EXTENSION("d128", D128, (LSE128), (), (), "d128")
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index e8bd8c73c12..d5c4a42e96d 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -410,6 +410,9 @@ constexpr auto AARCH64_FL_DEFAULT_ISA_MODE ATTRIBUTE_UNUSED
/* CSSC instructions are enabled through +cssc.  */
#define TARGET_CSSC AARCH64_HAVE_ISA (CSSC)

+/* CB<cc> instructions are enabled through +cmpbr.  */
+#define TARGET_CMPBR AARCH64_HAVE_ISA (CMPBR)
+
/* Make sure this is always defined so we don't have to check for ifdefs
    but rather use normal ifs.  */
#ifndef TARGET_FIX_ERR_A53_835769_DEFAULT
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 32bc45725de..3f05e5e0e34 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -22252,6 +22252,9 @@ Enable the FlagM2 flag conversion instructions.
Enable the Pointer Authentication Extension.
@item cssc
Enable the Common Short Sequence Compression instructions.
+@item cmpbr
+Enable the shorter compare and branch instructions, @code{cbb}, @code{cbh} and
+@code{cb}.
@item sme
Enable the Scalable Matrix Extension.  This is only supported when SVE2 is also
enabled.
--
2.45.2