Re: [PATCH v2 1/1] aarch64: Assume function's are non-streaming unless annotated [PR126133]

[Karl Meakin]

On 19/08/2026 16:15, Alice Carlotti wrote:

On Wed, Jul 22, 2026 at 01:41:31PM +0000, Karl Meakin via Sourceware Forge 
wrote:

From: Karl Meakin <karl.mea...@arm.com>

Make `aarch64_update_ipa_fn_target_info` more conservative, by setting
the `AARCH64_IPA_SM_FIXED` bit by default. The bit will only be unset if
the function is annotated with `[[arm::streaming_compatible]]`. This
matches the ACLE's specification which states that functions are by
default non-streaming.

This fixes PR 126133 by causing inlining to fail, even with
`[[gnu::always_inline]]`, because the target features do not match.

gcc/ChangeLog:

        * config/aarch64/aarch64.cc (aarch64_update_ipa_fn_target_info):
        set the `AARCH64_IPA_SM_FIXED` bit unless the function is
        annotated with `[[arm::streaming_compatible]]`.

gcc/testsuite/ChangeLog:

        * gcc.target/aarch64/pr126133-1.c: New test.
        * gcc.target/aarch64/pr126133-2.c: New test.
        * gcc.target/aarch64/pr126133-3.c: New test.
---
  gcc/config/aarch64/aarch64.cc                 | 15 ++++++-------
  gcc/testsuite/gcc.target/aarch64/pr126133-1.c | 19 +++++++++++++++++
  gcc/testsuite/gcc.target/aarch64/pr126133-2.c | 21 +++++++++++++++++++
  gcc/testsuite/gcc.target/aarch64/pr126133-3.c | 19 +++++++++++++++++
  4 files changed, 65 insertions(+), 9 deletions(-)
  create mode 100644 gcc/testsuite/gcc.target/aarch64/pr126133-1.c
  create mode 100644 gcc/testsuite/gcc.target/aarch64/pr126133-2.c
  create mode 100644 gcc/testsuite/gcc.target/aarch64/pr126133-3.c

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 61562c94a553..d4ed42ce73e1 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -22185,15 +22185,12 @@ aarch64_update_ipa_fn_target_info (unsigned int 
&info, const gimple *stmt)
      }
    if (auto *call = dyn_cast<const gcall *> (stmt))
      {
-      if (gimple_call_builtin_p (call, BUILT_IN_MD))
-       {
-         /* The attributes on AArch64 builtins are supposed to be accurate.
-            If the function isn't marked streaming-compatible then it
-            needs whichever SM mode it selects.  */
-         tree decl = gimple_call_fndecl (call);
-         if (aarch64_fndecl_pstate_sm (decl) != 0)
-           info |= AARCH64_IPA_SM_FIXED;
-       }
+      /* Assume functions are non-streaming by default.
+       They are only streaming or streaming-compatible if they have the
+       corresponding attribute.  */
+      tree decl = gimple_call_fndecl (call);
+      if (!decl || aarch64_fndecl_pstate_sm (decl) != 0)
+       info |= AARCH64_IPA_SM_FIXED;
      }
    return true;
  }

This change doesn't go far enough.  I have proposed a more comprehensive fix -
see https://gcc.gnu.org/pipermail/gcc-patches/2026-August/728155.html.

Alice

Thanks, I will defer to your patch