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.
Tested on aarch64-linux-gnu (with and without SVE), aarch64_be-elf and
x86_64-linux-gnu. OK to install?
Richard
2018-05-30 Richard Sandiford <richard.sandif...@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.
Index: gcc/expr.c
===================================================================
--- gcc/expr.c 2018-05-30 07:33:11.652009370 +0100
+++ gcc/expr.c 2018-05-30 07:44:31.856060230 +0100
@@ -10582,6 +10582,8 @@ expand_expr_real_1 (tree exp, rtx target
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)));
Index: gcc/testsuite/gcc.target/aarch64/sve/extract_5.c
===================================================================
--- /dev/null 2018-04-20 16:19:46.369131350 +0100
+++ gcc/testsuite/gcc.target/aarch64/sve/extract_5.c 2018-05-30
07:44:31.857060190 +0100
@@ -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;
+}
