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Re: RFC: PR 19650

On Jan 27, 2005, at 2:19 PM, Roger Sayle wrote:
if (lhs == 0)
+ {
+ true_value = fold_convert (type, true_value);
! lhs = fold (cond_first_p ? build2 (code, type, true_value, arg)
! : build2 (code, type, arg, true_value));
+ }
if (rhs == 0)
+ {
+ false_value = fold_convert (type, false_value);
! rhs = fold (cond_first_p ? build2 (code, type, false_value, arg)
! : build2 (code, type, arg, false_value));
+ }

Could you see if this untested suggestion works for you?

Unfortunately, this breaks bootstrap on ppc due to miscompiling some of the PPC-specific
code, which boils down to this loop:

unsigned int i;
for (i = 0;
((i) < 4 ? (i) + 3 : (~(unsigned int) 0)) != (~(unsigned int) 0);

Yes, that is a stupid way to write i=4, but there it is (well hidden by macros of course).
fold is presented with the following:

<ne_expr 0x4267e4e0
type <integer_type 0x4260b680 int public SI
arg 0 <cond_expr 0x4267e4b0
type <integer_type 0x4260b700 unsigned int public unsigned SI
arg 0 <le_expr 0x4267e450 type <integer_type 0x4260b680 int>
arg 0 <var_decl 0x42680880 i>
arg 1 <integer_cst 0x42684000 constant invariant 3>>
arg 1 <plus_expr 0x4267e480 type <integer_type 0x4260b700 unsigned int>
arg 0 <var_decl 0x42680880 i>
arg 1 <integer_cst 0x42684000 3>>
arg 2 <integer_cst 0x42606640 constant invariant 4294967295>>
arg 1 <integer_cst 0x42606640 4294967295>>

and the transformation above changes 4294967295 to -1, which compares as != 429467295.
Now what? Perhaps the transformation should not be applied in the COND_EXPR case?

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