https://gcc.gnu.org/g:771dfe6e2427cb06c5046b06e7342485b6fd6e51
commit r15-10822-g771dfe6e2427cb06c5046b06e7342485b6fd6e51 Author: Alice Carlotti <[email protected]> Date: Wed Jan 14 13:48:35 2026 +0000 aarch64: Disable shrink-wrap for locally-streaming functions [PR 123624] The meaning of poly_int values changes depending on whether we are in streaming or non-streaming mode, but this dependency is not explicitly tracked. Locally-streaming functions can change streaming state in the prologue and epilogue, so it is unsafe to apply shrink wrapping to these functions, as doing so could change the mode seen by instructions like cntd. gcc/ChangeLog: PR target/123624 * config/aarch64/aarch64-protos.h (aarch64_use_simple_return_insn_p): New. * config/aarch64/aarch64.cc (aarch64_use_simple_return_insn_p): New, used... * config/aarch64/aarch64.md (simple_return): ...here. gcc/testsuite/ChangeLog: PR target/123624 * gcc.target/aarch64/sme/sme-shrinkwrap.c: New test. Diff: --- gcc/config/aarch64/aarch64-protos.h | 1 + gcc/config/aarch64/aarch64.cc | 14 ++++ gcc/config/aarch64/aarch64.md | 2 +- .../gcc.target/aarch64/sme/sme-shrinkwrap.c | 78 ++++++++++++++++++++++ 4 files changed, 94 insertions(+), 1 deletion(-) diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h index 8f44aea2367a..e1caf802d661 100644 --- a/gcc/config/aarch64/aarch64-protos.h +++ b/gcc/config/aarch64/aarch64-protos.h @@ -970,6 +970,7 @@ bool aarch64_uimm12_shift (unsigned HOST_WIDE_INT); int aarch64_movk_shift (const wide_int_ref &, const wide_int_ref &); bool aarch64_is_mov_xn_imm (unsigned HOST_WIDE_INT); bool aarch64_use_return_insn_p (void); +bool aarch64_use_simple_return_insn_p (void); const char *aarch64_output_casesi (rtx *); const char *aarch64_output_load_tp (rtx); const char *aarch64_output_sme_zero_za (rtx); diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc index 21be53d2ee80..a39e7c0eaef6 100644 --- a/gcc/config/aarch64/aarch64.cc +++ b/gcc/config/aarch64/aarch64.cc @@ -10110,6 +10110,20 @@ aarch64_use_return_insn_p (void) return known_eq (cfun->machine->frame.frame_size, 0); } +/* Return false for locally streaming functions in order to avoid + shrink-wrapping them. Shrink-wrapping is unsafe when the function prologue + and epilogue contain streaming state change, because these implicitly change + the meaning of poly_int values. */ + +bool +aarch64_use_simple_return_insn_p (void) +{ + if (aarch64_cfun_enables_pstate_sm ()) + return false; + + return true; +} + /* Generate the epilogue instructions for returning from a function. This is almost exactly the reverse of the prolog sequence, except that we need to insert barriers to avoid scheduling loads that read diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md index 87d6e443717e..7dbbfb668a73 100644 --- a/gcc/config/aarch64/aarch64.md +++ b/gcc/config/aarch64/aarch64.md @@ -1116,7 +1116,7 @@ (define_insn "simple_return" [(simple_return)] - "" + "aarch64_use_simple_return_insn_p ()" { output_asm_insn ("ret", operands); return aarch64_sls_barrier (aarch64_harden_sls_retbr_p ()); diff --git a/gcc/testsuite/gcc.target/aarch64/sme/sme-shrinkwrap.c b/gcc/testsuite/gcc.target/aarch64/sme/sme-shrinkwrap.c new file mode 100644 index 000000000000..b8dfd5f92f62 --- /dev/null +++ b/gcc/testsuite/gcc.target/aarch64/sme/sme-shrinkwrap.c @@ -0,0 +1,78 @@ +/* { dg-options "-O3 -fshrink-wrap" } */ +/* { dg-do run { target { aarch64_sme_hw && aarch64_sve_hw } } } */ +/* { dg-do compile { target { ! { aarch64_sme_hw && aarch64_sve_hw } } } } */ +/* { dg-final { check-function-bodies "**" "" } } */ + +#include <arm_sme.h> + +#pragma GCC target "+sve" + +[[gnu::noipa]] +__arm_streaming +int callee (int x) +{ + return 0; +} + +/* +** foo: +** cbnz w0, [^\n]* +** cntd x0 +** ret +** ... +*/ +__arm_streaming +int foo(int x) +{ + if (x) + return callee(3); + return svcntd(); +} + +/* +** bar: +** ... +** smstart [^\n]* +** ... +** ( +** cntd [^\n]* +** ... +** cbn?z [^\n]* +** | +** cbn?z [^\n]* +** ... +** cntd [^\n]* +** ) +** ... +*/ + +__arm_locally_streaming +int bar(int x) +{ + if (x) + return callee(3); + return svcntd(); +} + +/* +** baz: +** cbnz w0, [^\n]* +** cntd x0 +** ret +** ... +*/ +__arm_streaming +int baz(int x) +{ + if (x) + return callee(3); + return svcntd(); +} + +[[gnu::noipa]] +int main() +{ + if (bar(0) != svcntsd()) + __builtin_abort(); + return 0; +}
