Fix expand_expr_real_1 handling of BLKmode bitfield references

The handling of bitfield references in expand_expr_real_1 includes:

            machine_mode ext_mode = mode;

            if (ext_mode == BLKmode
                && ! (target != 0 && MEM_P (op0)
                      && MEM_P (target)
                      && multiple_p (bitpos, BITS_PER_UNIT)))
              ext_mode = int_mode_for_size (bitsize, 1).else_blk ();

            if (ext_mode == BLKmode)
              {
                [...]
                gcc_assert (MEM_P (op0)

Here "mode" is the TYPE_MODE of the result, so when mode == BLKmode,
the target must be a MEM if nonnull, since no other rtl objects can
have BLKmode.  But there's no guarantee that the source value op0 is also
BLKmode and thus also a MEM: we can reach the assert for any source if
the bitsize being extracted is larger than the largest integer mode
(or larger than MAX_FIXED_MODE_SIZE).

This triggered for SVE with -msve-vector-bits=512, where we could
sometimes try to extract a BLKmode value from a 512-bit vector,
and where int_mode_for_size would rightly fail for large bitsizes.

The patch reuses the existing:

	/* Otherwise, if this is a constant or the object is not in memory
	   and need be, put it there.  */
	else if (CONSTANT_P (op0) || (!MEM_P (op0) && must_force_mem))
	  {
	    memloc = assign_temp (TREE_TYPE (tem), 1, 1);
	    emit_move_insn (memloc, op0);
	    op0 = memloc;
	    clear_mem_expr = true;
	  }

to handle this case.

2018-05-29  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* expr.c (expand_expr_real_1): Force the operand into memory if
	its TYPE_MODE is BLKmode and if there is no integer mode for
	the number of bits being extracted.

gcc/testsuite/
	* gcc.target/aarch64/sve/extract_5.c: New test.

From-SVN: r261150

4 files changed, 83 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index eea0298..7854103 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-06-04  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	* expr.c (expand_expr_real_1): Force the operand into memory if
+	its TYPE_MODE is BLKmode and if there is no integer mode for
+	the number of bits being extracted.
+
 2018-06-04  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/85832
diff --git a/gcc/expr.c b/gcc/expr.c
index 1fa3227..f15037a 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -10579,6 +10579,8 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 	   to a larger size.  */
 	must_force_mem = (offset
 			  || mode1 == BLKmode
+			  || (mode == BLKmode
+			      && !int_mode_for_size (bitsize, 1).exists ())
 			  || maybe_gt (bitpos + bitsize,
 				       GET_MODE_BITSIZE (mode2)));
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 043a4f4..459958e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2018-06-04  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	* gcc.target/aarch64/sve/extract_5.c: New test.
+
 2018-06-04  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/85832
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/extract_5.c b/gcc/testsuite/gcc.target/aarch64/sve/extract_5.c
new file mode 100644
index 0000000..652ba83
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/extract_5.c
@@ -0,0 +1,71 @@
+/* Originally from gcc.dg/vect/vect-alias-check-10.c.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-vectorize -msve-vector-bits=512" } */
+
+#define N 87
+#define M 6
+
+typedef signed char sc;
+typedef unsigned char uc;
+typedef signed short ss;
+typedef unsigned short us;
+typedef int si;
+typedef unsigned int ui;
+typedef signed long long sll;
+typedef unsigned long long ull;
+
+#define FOR_EACH_TYPE(M) \
+  M (sc) M (uc) \
+  M (ss) M (us) \
+  M (si) M (ui) \
+  M (sll) M (ull) \
+  M (float) M (double)
+
+#define TEST_VALUE(I) ((I) * 5 / 2)
+
+#define ADD_TEST(TYPE)				\
+  void __attribute__((noinline, noclone))	\
+  test_##TYPE (TYPE *a, int step)		\
+  {						\
+    for (int i = 0; i < N; ++i)			\
+      {						\
+	a[i * step + 0] = a[i * step + 0] + 1;	\
+	a[i * step + 1] = a[i * step + 1] + 2;	\
+	a[i * step + 2] = a[i * step + 2] + 4;	\
+	a[i * step + 3] = a[i * step + 3] + 8;	\
+      }						\
+  }						\
+  void __attribute__((noinline, noclone))	\
+  ref_##TYPE (TYPE *a, int step)		\
+  {						\
+    for (int i = 0; i < N; ++i)			\
+      {						\
+	a[i * step + 0] = a[i * step + 0] + 1;	\
+	a[i * step + 1] = a[i * step + 1] + 2;	\
+	a[i * step + 2] = a[i * step + 2] + 4;	\
+	a[i * step + 3] = a[i * step + 3] + 8;	\
+	asm volatile ("");			\
+      }						\
+  }
+
+#define DO_TEST(TYPE)					\
+  for (int j = -M; j <= M; ++j)				\
+    {							\
+      TYPE a[N * M], b[N * M];				\
+      for (int i = 0; i < N * M; ++i)			\
+	a[i] = b[i] = TEST_VALUE (i);			\
+      int offset = (j < 0 ? N * M - 4 : 0);		\
+      test_##TYPE (a + offset, j);			\
+      ref_##TYPE (b + offset, j);			\
+      if (__builtin_memcmp (a, b, sizeof (a)) != 0)	\
+	__builtin_abort ();				\
+    }
+
+FOR_EACH_TYPE (ADD_TEST)
+
+int
+main (void)
+{
+  FOR_EACH_TYPE (DO_TEST)
+  return 0;
+}