On Wed, 20 Aug 2014, Marc Glisse wrote: > On Wed, 20 Aug 2014, Richard Biener wrote: > > > 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? > > Yes, that looks fine. > > (fold-const.c checks TREE_OVERFLOW(@1), I don't know about that)
Not sure why it does that. > (we are obviously losing the warning) Yes. I have no idea how to preserve those - I'd have to invent a similar API as fold() does to defer warnings. Other than that adding some special syntax just for the overflow warnings is of course possible. Richard.
