[PATCH] aarch64: Validate register operands early in ldp fusion pass [PR113062]

[Alex Coplan]

We were missing validation of the candidate register operands in the
ldp/stp pass.  I was relying on recog rejecting such cases when we
formed the final pair insn, but the testcase shows that with
-fharden-conditionals we attempt to combine two insns with asm_operands,
both containing mem rtxes.  This then trips the assert:

gcc_assert (change->new_uses.is_valid ());

in the stp case as we aren't expecting to have (distinct) uses of mem in
the candidate stores.

Bootstrapped/regtested on aarch64-linux-gnu, OK for trunk?

Thanks,
Alex

gcc/ChangeLog:

        PR target/113062
        * config/aarch64/aarch64-ldp-fusion.cc
        (ldp_bb_info::track_access): Punt on accesses with invalid
        register operands.

gcc/testsuite/ChangeLog:

        PR target/113062
        * gcc.dg/pr113062.c: New test.

diff --git a/gcc/config/aarch64/aarch64-ldp-fusion.cc 
b/gcc/config/aarch64/aarch64-ldp-fusion.cc
index 327ba4e417d..273db8c582f 100644
--- a/gcc/config/aarch64/aarch64-ldp-fusion.cc
+++ b/gcc/config/aarch64/aarch64-ldp-fusion.cc
@@ -476,6 +476,12 @@ ldp_bb_info::track_access (insn_info *insn, bool load_p, 
rtx mem)
 
   const lfs_fields lfs = { load_p, fpsimd_op_p, mem_size };
 
+  // Ignore the access if the register operand isn't suitable for ldp/stp.
+  if (!REG_P (reg_op)
+      && !SUBREG_P (reg_op)
+      && (load_p || !aarch64_const_zero_rtx_p (reg_op)))
+    return;
+
   if (track_via_mem_expr (insn, mem, lfs))
     return;
 
diff --git a/gcc/testsuite/gcc.dg/pr113062.c b/gcc/testsuite/gcc.dg/pr113062.c
new file mode 100644
index 00000000000..5667c17b0f6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr113062.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-Oz -fharden-conditional-branches" } */
+long double foo;
+double bar;
+void abort();
+void check() {
+  if (foo == bar)
+    abort();
+}
+