[GCC 14] aarch64: Add another use of force_subreg [PR115464]

[Richard Sandiford]

I'd like to backport r15-1244 to GCC 14 and then apply the patch below.

===

This patch includes the testcase from r15-1399 plus a miminal
fix for it, without the other proactive uses of force_subreg.
We can backport other force_subreg calls later if they're shown
to be needed.

Boostrapped & regression-tested on aarch64-linux-gnu.  I'll leave
a bit of time for comments and then push on Monday if no-one has any
objections before then.

Richard


gcc/
        PR target/115464
        * config/aarch64/aarch64-sve-builtins-base.cc
        (svset_neonq_impl::expand): Use force_subreg instead of
        lowpart_subreg.

gcc/testsuite/
        PR target/115464
        * gcc.target/aarch64/sve/acle/general/pr115464_2.c: New test.
---
 gcc/config/aarch64/aarch64-sve-builtins-base.cc       |  4 +++-
 .../gcc.target/aarch64/sve/acle/general/pr115464_2.c  | 11 +++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 
gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr115464_2.c

diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc 
b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
index c9182594bc1..241a249503f 100644
--- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
+++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
@@ -1185,7 +1185,9 @@ public:
     if (BYTES_BIG_ENDIAN)
       return e.use_exact_insn (code_for_aarch64_sve_set_neonq (mode));
     insn_code icode = code_for_vcond_mask (mode, mode);
-    e.args[1] = lowpart_subreg (mode, e.args[1], GET_MODE (e.args[1]));
+    e.args[1] = force_subreg (mode, e.args[1], GET_MODE (e.args[1]),
+                             subreg_lowpart_offset (mode,
+                                                    GET_MODE (e.args[1])));
     e.add_output_operand (icode);
     e.add_input_operand (icode, e.args[1]);
     e.add_input_operand (icode, e.args[0]);
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr115464_2.c 
b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr115464_2.c
new file mode 100644
index 00000000000..f561c34f732
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr115464_2.c
@@ -0,0 +1,11 @@
+/* { dg-options "-O2" } */
+
+#include <arm_neon.h>
+#include <arm_sve.h>
+#include <arm_neon_sve_bridge.h>
+
+svuint16_t
+convolve4_4_x (uint16x8x2_t permute_tbl, svuint16_t a)
+{
+    return svset_neonq_u16 (a, permute_tbl.val[1]);
+}
-- 
2.25.1