On Thu, 13 Jul 2017, Jakub Jelinek wrote:
> Hi!
>
> As mentioned in the PR, the following testcase started using recently
> BIT_FIELD_REFs instead of MEM_REFs and thus the bswap pass, while it
> properly determines the very long sequence of stmts is a nop transformation,
> throws that away and doesn't optimize it, and no other optimizations
> are able to optimize it away.
>
> The patch attempts to not do anything if there is a simple identity
> copy, but if the nop reshuffle needs more than one operation, it will
> try to replace the final SSA_NAME BIT_IOR_EXPR assignment with assignment
> from the src value (typically SSA_NAME).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2017-07-13 Jakub Jelinek <[email protected]>
>
> PR tree-optimization/81396
> * tree-ssa-math-opts.c (struct symbolic_number): Add n_ops field.
> (init_symbolic_number): Initialize it to 1.
> (perform_symbolic_merge): Add n_ops from both operands into the new
> n_ops.
> (find_bswap_or_nop): Don't consider n->n == cmpnop computations
> without base_addr as useless if they need more than one operation.
> (bswap_replace): Handle !bswap case for NULL base_addr.
>
> * gcc.dg/tree-ssa/pr81396.c: New test.
>
> --- gcc/tree-ssa-math-opts.c.jj 2017-07-06 20:31:43.000000000 +0200
> +++ gcc/tree-ssa-math-opts.c 2017-07-13 19:27:02.985354778 +0200
> @@ -1968,6 +1968,7 @@ struct symbolic_number {
> tree alias_set;
> tree vuse;
> unsigned HOST_WIDE_INT range;
> + int n_ops;
> };
Ok if you document n_ops a bit in the comment above the structure.
Thanks,
Richard.
> #define BITS_PER_MARKER 8
> @@ -2083,6 +2084,7 @@ init_symbolic_number (struct symbolic_nu
> return false;
> n->range = size;
> n->n = CMPNOP;
> + n->n_ops = 1;
>
> if (size < 64 / BITS_PER_MARKER)
> n->n &= ((uint64_t) 1 << (size * BITS_PER_MARKER)) - 1;
> @@ -2293,6 +2295,7 @@ perform_symbolic_merge (gimple *source_s
> return NULL;
> }
> n->n = n1->n | n2->n;
> + n->n_ops = n1->n_ops + n2->n_ops;
>
> return source_stmt;
> }
> @@ -2588,7 +2591,7 @@ find_bswap_or_nop (gimple *stmt, struct
> return NULL;
>
> /* Useless bit manipulation performed by code. */
> - if (!n->base_addr && n->n == cmpnop)
> + if (!n->base_addr && n->n == cmpnop && n->n_ops == 1)
> return NULL;
>
> n->range *= BITS_PER_UNIT;
> @@ -2747,6 +2750,36 @@ bswap_replace (gimple *cur_stmt, gimple
> }
> src = val_tmp;
> }
> + else if (!bswap)
> + {
> + gimple *g;
> + if (!useless_type_conversion_p (TREE_TYPE (tgt), TREE_TYPE (src)))
> + {
> + if (!is_gimple_val (src))
> + return false;
> + g = gimple_build_assign (tgt, NOP_EXPR, src);
> + }
> + else
> + g = gimple_build_assign (tgt, src);
> + if (n->range == 16)
> + nop_stats.found_16bit++;
> + else if (n->range == 32)
> + nop_stats.found_32bit++;
> + else
> + {
> + gcc_assert (n->range == 64);
> + nop_stats.found_64bit++;
> + }
> + if (dump_file)
> + {
> + fprintf (dump_file,
> + "%d bit reshuffle in target endianness found at: ",
> + (int) n->range);
> + print_gimple_stmt (dump_file, cur_stmt, 0);
> + }
> + gsi_replace (&gsi, g, true);
> + return true;
> + }
> else if (TREE_CODE (src) == BIT_FIELD_REF)
> src = TREE_OPERAND (src, 0);
>
> --- gcc/testsuite/gcc.dg/tree-ssa/pr81396.c.jj 2017-07-13
> 19:22:10.191954620 +0200
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr81396.c 2017-07-13 19:24:16.638399984
> +0200
> @@ -0,0 +1,25 @@
> +/* PR tree-optimization/81396 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +typedef unsigned long long uint64_t;
> +
> +uint64_t
> +foo (uint64_t word)
> +{
> +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ && __SIZEOF_LONG_LONG__ == 8
> + const unsigned char *const ptr = (const unsigned char *) &word;
> + return ((uint64_t) ptr[0]
> + | ((uint64_t) ptr[1] << 8)
> + | ((uint64_t) ptr[2] << (8 * 2))
> + | ((uint64_t) ptr[3] << (8 * 3))
> + | ((uint64_t) ptr[4] << (8 * 4))
> + | ((uint64_t) ptr[5] << (8 * 5))
> + | ((uint64_t) ptr[6] << (8 * 6))
> + | ((uint64_t) ptr[7] << (8 * 7)));
> +#else
> + return word;
> +#endif
> +}
> +
> +/* { dg-final { scan-tree-dump "return word_\[0-9]*\\(D\\);" "optimized" } }
> */
>
> Jakub
>
>
--
Richard Biener <[email protected]>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
