On December 29, 2014 3:04:36 PM CET, Thomas Preud'homme
<thomas.preudho...@arm.com> wrote:
>Since 16bit byteswap can be done via an 8 bit rotation (and it is the
>canonical form),
>the check for an optab only serves to prevent the bswap optimization
>for
>targets that don't have a 16bit byteswap (but do have a rotation
>instruction). See
>PR63259 (comments 6 and onwards) for more details.
OK, but what about targets without a rotation optab? Is the fallback expansion
reasonable in all cases?
Richard.
>ChangeLog entry is as follows:
>
>2014-12-24 Thomas Preud'homme thomas.preudho...@arm.com
>
>PR tree-optimization/63259
>* tree-ssa-math-opts.c (pass_optimize_bswap::execute): Stop checking
>if optab exists for 16bit byteswap.
>
>
>diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
>index 1ed2838..c175e88 100644
>--- a/gcc/tree-ssa-math-opts.c
>+++ b/gcc/tree-ssa-math-opts.c
>@@ -2350,15 +2350,13 @@ unsigned int
> pass_optimize_bswap::execute (function *fun)
> {
> basic_block bb;
>- bool bswap16_p, bswap32_p, bswap64_p;
>+ bool bswap32_p, bswap64_p;
> bool changed = false;
>- tree bswap16_type = NULL_TREE, bswap32_type = NULL_TREE,
>bswap64_type = NULL_TREE;
>+ tree bswap32_type = NULL_TREE, bswap64_type = NULL_TREE;
>
> if (BITS_PER_UNIT != 8)
> return 0;
>
>- bswap16_p = (builtin_decl_explicit_p (BUILT_IN_BSWAP16)
>- && optab_handler (bswap_optab, HImode) != CODE_FOR_nothing);
> bswap32_p = (builtin_decl_explicit_p (BUILT_IN_BSWAP32)
> && optab_handler (bswap_optab, SImode) != CODE_FOR_nothing);
> bswap64_p = (builtin_decl_explicit_p (BUILT_IN_BSWAP64)
>@@ -2367,12 +2365,6 @@ pass_optimize_bswap::execute (function *fun)
>
> /* Determine the argument type of the builtins. The code later on
> assumes that the return and argument type are the same. */
>- if (bswap16_p)
>- {
>- tree fndecl = builtin_decl_explicit (BUILT_IN_BSWAP16);
>- bswap16_type = TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (fndecl)));
>- }
>-
> if (bswap32_p)
> {
> tree fndecl = builtin_decl_explicit (BUILT_IN_BSWAP32);
>@@ -2443,11 +2435,6 @@ pass_optimize_bswap::execute (function *fun)
> if (code == LROTATE_EXPR || code == RROTATE_EXPR)
> continue;
> load_type = uint16_type_node;
>- if (bswap16_p)
>- {
>- fndecl = builtin_decl_explicit (BUILT_IN_BSWAP16);
>- bswap_type = bswap16_type;
>- }
> break;
> case 32:
> load_type = uint32_type_node;
>@@ -2469,7 +2456,7 @@ pass_optimize_bswap::execute (function *fun)
> continue;
> }
>
>- if (bswap && !fndecl)
>+ if (bswap && !fndecl && n.range != 16)
> continue;
>
> if (bswap_replace (cur_stmt, src_stmt, fndecl, bswap_type,
>load_type,
>
>Bootstrapped on x86_64-linux-gnu and aarch64-none-linux-gnu without any
>testsuite regression
>
>Is this ok for trunk?
>
>Best regards,
>
>Thomas
