gnu /
gcc /
32b21292adb6ad6b5e1d60d923a773e4d0daca7b aarch64: Fix invalid nested subregs [PR115464]
The testcase extracts one arm_neon.h vector from a pair (one subreg)
and then reinterprets the result as an SVE vector (another subreg).
Each subreg makes sense individually, but we can't fold them together
into a single subreg: it's 32 bytes -> 16 bytes -> 16*N bytes,
but the interpretation of 32 bytes -> 16*N bytes depends on
whether N==1 or N>1.
Since the second subreg makes sense individually, simplify_subreg
should bail out rather than ICE on it. simplify_gen_subreg will
then do the same (because it already checks validate_subreg).
This leaves simplify_gen_subreg returning null, requiring the
caller to take appropriate action.
I think this is relatively likely to occur elsewhere, so the patch
adds a helper for forcing a subreg, allowing a temporary pseudo to
be created where necessary.
I'll follow up by using force_subreg in more places. This patch
is intended to be a minimal backportable fix for the PR.
gcc/
PR target/115464
* simplify-rtx.cc (simplify_context::simplify_subreg): Don't try
to fold two subregs together if their relationship isn't known
at compile time.
* explow.h (force_subreg): Declare.
* explow.cc (force_subreg): New function.
* config/aarch64/aarch64-sve-builtins-base.cc
(svset_neonq_impl::expand): Use it instead of simplify_gen_subreg.
gcc/testsuite/
PR target/115464
* gcc.target/aarch64/sve/acle/general/pr115464.c: New test.
(cherry picked from commit 0970ff46ba6330fc80e8736fc05b2eaeeae0b6a0)
5 files changed
