Re: [PATCH] aarch64: Add +lse128 architectural extension command-line flag

[Victor Do Nascimento]

On 3/26/24 12:26, Richard Sandiford wrote:
Victor Do Nascimento <victor.donascime...@arm.com> writes:
Given how, at present, the choice of using LSE128 atomic instructions
by the toolchain is delegated to run-time selection in the form of
Libatomic ifuncs, responsible for querying target support, the
`+lse128' target architecture compile-time flag is absent from GCC.
This, however, contrasts with the Binutils implementation, which gates
LSE128 instructions behind the `+lse128' flag.  This can lead to
problems in GCC for certain use-cases.  One such example is in the use
of inline assembly, whereby the inability of enabling the feature in
the command-line prevents the compiler from automatically issuing the
necessary LSE128 `.arch' directive.

This patch therefore brings GCC into alignment with LLVM and Binutils
in adding support for the `+lse128' architectural extension flag.

gcc/ChangeLog:

        * config/aarch64/aarch64-option-extensions.def: Add LSE128
        AARCH64_OPT_EXTENSION, adding it as a dependency for the D128
        feature.

gcc/testsuite/ChangeLog:

        * gcc.target/aarch64/lse128-flag.c: New.
        * gcc.target/aarch64/cpunative/info_23: Likewise.
        * gcc.target/aarch64/cpunative/native_cpu_23.c: Likewise.

The new extension should be documented in doc/invoke.texi.

---
  gcc/config/aarch64/aarch64-option-extensions.def      |  4 +++-
  gcc/testsuite/gcc.target/aarch64/cpunative/info_23    |  8 ++++++++
  .../gcc.target/aarch64/cpunative/native_cpu_23.c      | 11 +++++++++++
  gcc/testsuite/gcc.target/aarch64/lse128-flag.c        | 10 ++++++++++
  4 files changed, 32 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/gcc.target/aarch64/cpunative/info_23
  create mode 100644 gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_23.c
  create mode 100644 gcc/testsuite/gcc.target/aarch64/lse128-flag.c

diff --git a/gcc/config/aarch64/aarch64-option-extensions.def 
b/gcc/config/aarch64/aarch64-option-extensions.def
index 1a3b91c68cf..ac54b899a06 100644
--- a/gcc/config/aarch64/aarch64-option-extensions.def
+++ b/gcc/config/aarch64/aarch64-option-extensions.def
@@ -275,7 +275,9 @@ AARCH64_OPT_EXTENSION("mops", MOPS, (), (), (), "")
  
  AARCH64_OPT_EXTENSION("cssc", CSSC, (), (), (), "cssc")
  
-AARCH64_OPT_EXTENSION("d128", D128, (), (), (), "d128")
+AARCH64_OPT_EXTENSION("lse128", LSE128, (LSE), (), (), "lse128")
+
+AARCH64_OPT_EXTENSION("d128", D128, (LSE128), (), (), "d128")
  
  AARCH64_OPT_EXTENSION("the", THE, (), (), (), "the")
  
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/info_23 b/gcc/testsuite/gcc.target/aarch64/cpunative/info_23
new file mode 100644
index 00000000000..d77c25d2f61
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/info_23
@@ -0,0 +1,8 @@
+processor      : 0
+BogoMIPS       : 100.00
+Features       : fp asimd evtstrm aes pmull sha1 sha2 crc32 asimddp atomics 
lse128
+CPU implementer        : 0xfe
+CPU architecture: 8
+CPU variant    : 0x0
+CPU part       : 0xd08
+CPU revision   : 2
\ No newline at end of file
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_23.c 
b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_23.c
new file mode 100644
index 00000000000..8a1e235d8ab
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_23.c
@@ -0,0 +1,11 @@
+/* { dg-do compile { target { { aarch64*-*-linux*} && native } } } */
+/* { dg-set-compiler-env-var GCC_CPUINFO 
"$srcdir/gcc.target/aarch64/cpunative/info_23" } */
+/* { dg-additional-options "-mcpu=native" } */
+
+int main()
+{
+  return 0;
+}
+
+/* { dg-final { scan-assembler {\.arch armv8-a\+dotprod\+crc\+crypto\+lse128} 
} } */
+/* Test one where lse128 is available and so should be emitted.  */
diff --git a/gcc/testsuite/gcc.target/aarch64/lse128-flag.c 
b/gcc/testsuite/gcc.target/aarch64/lse128-flag.c
new file mode 100644
index 00000000000..71339c3af6d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/lse128-flag.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target { aarch64*-*-*} } } */
+/* { dg-additional-options "-march=armv9.4-a+lse128" } */
+
+int main()
+{
+  return 0;
+}
+
+/* { dg-final { scan-assembler {\.arch armv9\.4-a\+crc\+lse128} } } */
+/* Test a normal looking procinfo.  */

Not sure I understand the comment.  Is procinfo part of this test?

Thank you for catching this, Richard.  This was originally a 
procinfo-reliant test which ended up being redesigned without reference 
to procinfo and this remained.  I've now dropped it from the patch.

Cheers!

Looks good otherwise.

Thanks,
Richard