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Re: Patch: Consistently generate widening multiplies


On Wed, Feb 17, 2010 at 12:00 AM, Bernd Schmidt <bernds_cb1@t-online.de> wrote:
> Tree-SSA introduced a regression with widening multiplications;
> extension operations are often separated from the MULT_EXPR they feed.
> There has been a patch last year to address this in expand_expr_real_2,
> but it's still rather more miss than hit as shown by the testcases
> included in the patch below.

Could this be http://gcc.gnu.org/PR29274 ? Would be a reason to push
the patch for gcc 4.5.

> This patch adds a new mini-pass to tree-ssa-math-opts.c.

*sigh* another mini-pass.  There are a handful of them now, and they
all cost a full traversal of the function for very local, very special
pattern matching things (bswap, etc.) They should be grouped somehow
:-(  I suppose there is no way to fold this into one of the existing
passes?


> +static unsigned int
> +execute_optimize_widening_mul (void)
(...)
> + ? ? ? ? ? ? if (rhs1_code != CONVERT_EXPR && rhs1_code != NOP_EXPR)
> + ? ? ? ? ? ? ? continue;

if (CONVERT_EXPR_CODE_P (rhs1_code)

Ciao!
Steven


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