Hi Stam,
> -----Original Message-----
> From: Stam Markianos-Wright <stam.markianos-wri...@arm.com>
> Sent: Friday, December 9, 2022 1:32 PM
> To: gcc-patches@gcc.gnu.org
> Cc: Kyrylo Tkachov <kyrylo.tkac...@arm.com>; Richard Earnshaw
> <richard.earns...@arm.com>; Ramana Radhakrishnan
> <ramana....@googlemail.com>; ni...@redhat.com
> Subject: [PATCH] Fix memory constraint on MVE v[ld/st][2/4] instructions
> [PR107714]
>
> Hi all,
>
> In the M-Class Arm-ARM:
>
> https://developer.arm.com/documentation/ddi0553/bu/?lang=en
>
> these MVE instructions only have '!' writeback variant and at:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107714
>
> we found that the Um constraint would also allow through a
> register offset writeback, resulting in an assembler error.
>
> Here I have added a new constraint and predicate for these
> instructions, which (uniquely, AFAICT), only support a `!` writeback
> increment by the data size (inside the compiler this is a POST_INC).
>
> No regressions in arm-none-eabi with MVE and MVE.FP.
>
> Ok for trunk, and backport to GCC11 and GCC12 (testing pending)?
>
> Thanks,
> Stam
>
> gcc/ChangeLog:
> PR target/107714
> * config/arm/arm-protos.h (mve_struct_mem_operand): New
> protoype.
> * config/arm/arm.cc (mve_struct_mem_operand): New function.
> * config/arm/constraints.md (Ug): New constraint.
> * config/arm/mve.md (mve_vst4q<mode>): Change constraint.
> (mve_vst2q<mode>): Likewise.
> (mve_vld4q<mode>): Likewise.
> (mve_vld2q<mode>): Likewise.
> * config/arm/predicates.md (mve_struct_operand): New predicate.
>
> gcc/testsuite/ChangeLog:
> PR target/107714
> * gcc.target/arm/mve/intrinsics/vldst24q_reg_offset.c: New test.
diff --git a/gcc/config/arm/constraints.md b/gcc/config/arm/constraints.md
index
e5a36d29c7135943b9bb5ea396f70e2e4beb1e4a..8908b7f5b15ce150685868e78e75280bf32053f1
100644
--- a/gcc/config/arm/constraints.md
+++ b/gcc/config/arm/constraints.md
@@ -474,6 +474,12 @@
(and (match_code "mem")
(match_test "TARGET_32BIT && arm_coproc_mem_operand (op, FALSE)")))
+(define_memory_constraint "Ug"
+ "@internal
+ In Thumb-2 state a valid MVE struct load/store address."
+ (and (match_code "mem")
+ (match_test "TARGET_HAVE_MVE && mve_struct_mem_operand (op)")))
+
I think you can define the constraints in terms of the new mve_struct_operand
predicate directly (see how we define the "Ua" constraint, for example).
Ok if that works (and testing passes of course).
Thanks,
Kyrill
