On Wed, 20 Aug 2014, Marc Glisse wrote:
> On Wed, 20 Aug 2014, Richard Biener wrote:
>
> > Committed.
> >
> > Also makes visible a desirable change I plan for if-exprs. They
> > should behave like outer ifs and allow us to write that series
> > of pattern as
> >
> > (for op in eq ne
> > /* Simplify X * C1 CMP 0 to X CMP 0 if C1 is not zero. */
> > (simplify
> > (op (mult @0 INTEGER_CST@1) integer_zerop@2)
> > /* In fold-const.c we have this and the following patterns
> > combined because there we can "compute" the operator
> > to use by using swap_tree_comparison. */
> > (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
> > (if (tree_int_cst_sgn (@1) > 0)
> > (op @0 @2))
> > (if (tree_int_cst_sgn (@1) < 0 && op == EQ_EXPR)
> > (ne @0 @2))
> > (if (tree_int_cst_sgn (@1) < 0 && op == NE_EXPR)
> > (eq @0 @2)))))
> >
> > that is, inner ifs have two operands, one condition and one
> > "result" (which can be another if). And the simplify
> > now has one mandatory match operand and at least one
> > result operand (if which all but the last have to be an
> > 'if').
>
> Not related to how you do "if" and such, but this simplification doesn't make
> sense. swap_tree_comparison preserves eq and ne, you only care that @1 is
> non-zero. It is for comparisons like lt that the sign can change the
> operation.
Oops, true (the fold_comparison code doesn't restrict itself to
eq and ne). So for ne and eq the sign of @1 doesn't matter.
So we can improve here and do
/* Simplify X * C1 CMP 0 to X CMP 0 if C1 is not zero. */
(for op in lt le eq ne ge gt
(simplify
(op (mult @0 INTEGER_CST@1) integer_zerop@2)
/* In fold-const.c we have this and the following pattern
combined because there we can "compute" the operator
to use by using swap_tree_comparison. Here we manage
to use only two patterns by swapping the operands instead
of changing the comparison code. */
(if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
&& tree_int_cst_sgn (@1) > 0))
(op @0 @2))
(simplify
(op (mult @0 INTEGER_CST@1) integer_zerop@2)
(if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
&& tree_int_cst_sgn (@1) < 0))
(op @2 @0)))
right?
Thanks,
Richard.
