On Wed, Nov 08, 2017 at 06:38:21PM +0100, Jakub Jelinek wrote:
> On Wed, Nov 08, 2017 at 05:17:50PM +0000, Joseph Myers wrote:
> > On Wed, 8 Nov 2017, Jakub Jelinek wrote:
> >
> > > of course only if LVAL is false. Additionally, I've added folding of
> > > "foo"[2] into 'o'. We have it in gimple-fold.c or so, so that one
> >
> > Note that if the 2 there comes from an overflowing expression that's not
> > valid as an extension to constant expressions in initializers (that is,
> >
> > static char c = "foo"[INT_MAX * -2];
> >
> > should result in an error with -pedantic-errors because of the overflow,
> > just as INT_MAX * -2 by itself wouldn't be a valid initializer in that
> > case).
> >
> > > Not sure about the COND_EXPR/VEC_COND_EXPR cases, right now I'm passing
> > > false as LVAL for the first operand (condition) and lval as LVAL for the
> > > other two (i.e. if called with lval == true on the whole *_COND_EXPR
> > > decl_constant_value_for_optimization etc. isn't performed on op1/op2,
> > > while
> > > without it it is). Can one take address of the whole COND_EXPR, or
> > > have it on LHS of anything in C? If not, perhaps I could just pass false
> > > in all the 3 calls. Though, then likely it would be called with lval ==
> > > false
> > > anyway.
> >
> > Conditional and compound expressions are never valid lvalues in C.
>
> Ok, so like this if it passes bootstrap/regtest?
>
> Changes from the last patch:
> 1) false instead of lval for COMPOUND_EXPR and *COND_EXPR op1/op2
So...
> @@ -278,21 +339,16 @@ c_fully_fold_internal (tree expr, bool i
> orig_op0 = op0 = TREE_OPERAND (expr, 0);
> orig_op1 = op1 = TREE_OPERAND (expr, 1);
> op0 = c_fully_fold_internal (op0, in_init, maybe_const_operands,
> - maybe_const_itself, for_int_const);
> + maybe_const_itself, for_int_const,
> + op0_lval);
> STRIP_TYPE_NOPS (op0);
> - if (code != MODIFY_EXPR
> - && code != PREDECREMENT_EXPR
> - && code != PREINCREMENT_EXPR
> - && code != POSTDECREMENT_EXPR
> - && code != POSTINCREMENT_EXPR)
> - op0 = decl_constant_value_for_optimization (op0);
> /* The RHS of a MODIFY_EXPR was fully folded when building that
> expression for the sake of conversion warnings. */
> if (code != MODIFY_EXPR)
> op1 = c_fully_fold_internal (op1, in_init, maybe_const_operands,
> - maybe_const_itself, for_int_const);
> + maybe_const_itself, for_int_const,
> + code == COMPOUND_EXPR ? lval : false);
...shouldn't we be passing just false here?
Marek
