[PATCH v4] DSE: Fix ICE after allow vector type in get_stored_val

[pan2.li@intel.com]

From: Pan Li <pan2.li@intel.com>

We allowed vector type for get_stored_val when read is less than or
equal to store in previous.  Unfortunately,  the valididate_subreg
treats the vector type's size is less than vector register as
invalid.  Then we will have ICE here.

This patch would like to fix it by filter-out the invalid type size,
and make sure the subreg is valid for both the read_mode and store_mode
before perform the real gen_lowpart.

The below test suites are passed for this patch:

* The x86 bootstrap test.
* The x86 regression test.
* The riscv rv64gcv regression test.
* The riscv rv64gc regression test.
* The aarch64 regression test.

gcc/ChangeLog:

	* dse.cc (get_stored_val): Make sure read_mode/write_mode
	is valid subreg before gen_lowpart.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/bug-6.c: New test.

Signed-off-by: Pan Li <pan2.li@intel.com>
---
 gcc/dse.cc                                    |  4 +++-
 .../gcc.target/riscv/rvv/base/bug-6.c         | 22 +++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/bug-6.c

diff --git a/gcc/dse.cc b/gcc/dse.cc
index edc7a1dfecf..1596da91da0 100644
--- a/gcc/dse.cc
+++ b/gcc/dse.cc
@@ -1946,7 +1946,9 @@ get_stored_val (store_info *store_info, machine_mode read_mode,
 				 copy_rtx (store_info->const_rhs));
   else if (VECTOR_MODE_P (read_mode) && VECTOR_MODE_P (store_mode)
     && known_le (GET_MODE_BITSIZE (read_mode), GET_MODE_BITSIZE (store_mode))
-    && targetm.modes_tieable_p (read_mode, store_mode))
+    && targetm.modes_tieable_p (read_mode, store_mode)
+    && validate_subreg (read_mode, store_mode, copy_rtx (store_info->rhs),
+			subreg_lowpart_offset (read_mode, store_mode)))
     read_reg = gen_lowpart (read_mode, copy_rtx (store_info->rhs));
   else
     read_reg = extract_low_bits (read_mode, store_mode,
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/bug-6.c b/gcc/testsuite/gcc.target/riscv/rvv/base/bug-6.c
new file mode 100644
index 00000000000..5bb00b8f587
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/bug-6.c
@@ -0,0 +1,22 @@
+/* Test that we do not have ice when compile */
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -ftree-vectorize" } */
+
+struct A { float x, y; };
+struct B { struct A u; };
+
+extern void bar (struct A *);
+
+float
+f3 (struct B *x, int y)
+{
+  struct A p = {1.0f, 2.0f};
+  struct A *q = &x[y].u;
+
+  __builtin_memcpy (&q->x, &p.x, sizeof (float));
+  __builtin_memcpy (&q->y, &p.y, sizeof (float));
+
+  bar (&p);
+
+  return x[y].u.x + x[y].u.y;
+}
-- 
2.34.1