On Wed, May 30, 2018 at 8:46 AM Richard Sandiford
<richard.sandif...@linaro.org> wrote:>
> 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?
Ok.
Richard.
> 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;
> +}
