aarch64: PR target/102252 Invalid addressing mode for SVE load predicate

In the testcase we generate invalid assembly for an SVE load predicate instruction.
The RTL for the insn is:
(insn 9 8 10 (set (reg:VNx16BI 68 p0)
        (mem:VNx16BI (plus:DI (mult:DI (reg:DI 1 x1 [93])
                    (const_int 8 [0x8]))
                (reg/f:DI 0 x0 [92])) [2 work_3(D)->array[offset_4(D)]+0 S8 A16]))

That addressing mode is not valid for the instruction [1] as it only accepts the addressing mode:
[<Xn|SP>{, #<imm>, MUL VL}]

This patch rejects the register index form for SVE predicate modes.

Bootstrapped and tested on aarch64-none-linux-gnu.

[1] https://developer.arm.com/documentation/ddi0602/2021-06/SVE-Instructions/LDR--predicate---Load-predicate-register-

gcc/ChangeLog:

	PR target/102252
	* config/aarch64/aarch64.c (aarch64_classify_address): Don't allow
	register index for SVE predicate modes.

gcc/testsuite/ChangeLog:

	PR target/102252
	* g++.target/aarch64/sve/pr102252.C: New test.

2 files changed, 42 insertions, 4 deletions

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 1fbe9e0..30d9a0b 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -9770,7 +9770,6 @@ aarch64_classify_address (struct aarch64_address_info *info,
 			    || mode == TImode
 			    || mode == TFmode
 			    || (BYTES_BIG_ENDIAN && advsimd_struct_p));
-
   /* If we are dealing with ADDR_QUERY_LDP_STP_N that means the incoming mode
      corresponds to the actual size of the memory being loaded/stored and the
      mode of the corresponding addressing mode is half of that.  */
@@ -9779,12 +9778,14 @@ aarch64_classify_address (struct aarch64_address_info *info,
     mode = DFmode;
 
   bool allow_reg_index_p = (!load_store_pair_p
-			    && (known_lt (GET_MODE_SIZE (mode), 16)
+			    && ((vec_flags == 0
+				 && known_lt (GET_MODE_SIZE (mode), 16))
 				|| vec_flags == VEC_ADVSIMD
 				|| vec_flags & VEC_SVE_DATA));
 
-  /* For SVE, only accept [Rn], [Rn, Rm, LSL #shift] and
-     [Rn, #offset, MUL VL].  */
+  /* For SVE, only accept [Rn], [Rn, #offset, MUL VL] and [Rn, Rm, LSL #shift].
+     The latter is not valid for SVE predicates, and that's rejected through
+     allow_reg_index_p above.  */
   if ((vec_flags & (VEC_SVE_DATA | VEC_SVE_PRED)) != 0
       && (code != REG && code != PLUS))
     return false;
diff --git a/gcc/testsuite/g++.target/aarch64/sve/pr102252.C b/gcc/testsuite/g++.target/aarch64/sve/pr102252.C
new file mode 100644
index 0000000..f90f121
--- /dev/null
+++ b/gcc/testsuite/g++.target/aarch64/sve/pr102252.C
@@ -0,0 +1,37 @@
+/* PR target/102252.  */
+/* { dg-do assemble { target aarch64_asm_sve_ok } } */
+/* { dg-options "-march=armv8.2-a+sve -msve-vector-bits=512" } */
+
+/* We used to generate invalid assembly for SVE predicate loads.  */
+
+#include <arm_sve.h>
+
+class SimdBool
+{
+private:
+    typedef svbool_t simdInternalType_ __attribute__((arm_sve_vector_bits(512)));
+
+public:
+    SimdBool() {}
+
+    simdInternalType_ simdInternal_;
+
+};
+
+static svfloat32_t selectByMask(svfloat32_t a, SimdBool m) {
+    return svsel_f32(m.simdInternal_, a, svdup_f32(0.0));
+}
+
+struct s {
+    SimdBool array[1];
+};
+
+
+
+void foo(struct s* const work, int offset)
+{
+        svfloat32_t tz_S0;
+
+        tz_S0 = selectByMask(tz_S0, work->array[offset]);
+}
+