Avoid creating (const (reg ...)) [PR108603]

convert_memory_address_addr_space_1 has two modes: one in which it
tries to create a self-contained RTL expression (which might fail)
and one in which it can emit new instructions where necessary.

When handling a CONST, the function recurses into the CONST's
operand and then constifies the result.  But that's only valid if
the result is still a self-contained expression.  If new instructions
have been emitted, the expression will refer to the (non-constant)
results of those instructions.

In the PR, this caused us to emit a nonsensical (const (reg ...))
REG_EQUAL note.

gcc/
	PR tree-optimization/108603
	* explow.cc (convert_memory_address_addr_space_1): Only wrap
	the result of a recursive call in a CONST if no instructions
	were emitted.

gcc/testsuite/
	PR tree-optimization/108603
	* gcc.target/aarch64/sve/pr108603.c: New test.

(cherry picked from commit b09dc74801cf4e19bdf5fcd18a5cd53fc9e9ca9a)

1 files changed, 8 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr108603.c b/gcc/testsuite/gcc.target/aarch64/sve/pr108603.c
new file mode 100644
index 0000000..a2aea9f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/pr108603.c
@@ -0,0 +1,8 @@
+/* { dg-options "-O2 -mabi=ilp32 -fdata-sections" } */
+
+int a[128];
+long long *p;
+void f() {
+  for (long i = 0; i < sizeof(long); i++)
+    p[i] = a[i];
+}