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Fix tree-optimization/103314 : Limit folding of (type) X op CST where type is a nop convert to gimple

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There is some re-association code in fold_binary which conflicts with
this optimization due keeping around some "constants" which are not
INTEGER_CST (1 << -1) so we end up in an infinite loop because of that.
So we need to limit this case to GIMPLE level only.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/103314

gcc/ChangeLog:

	* match.pd ((type) X op CST): Restrict the equal
	TYPE_PRECISION case to GIMPLE only.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr103314-1.c: New test.
This commit is contained in:
Andrew Pinski 2021-11-19 01:42:41 +00:00
parent 74a4ece02d
commit ea2954df43
2 changed files with 11 additions and 1 deletions
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6
gcc/match.pd
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@ -1619,7 +1619,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
after hoisting the conversion the operation will be narrower.
It is also a good if the conversion is a nop as moves the
conversion to one side; allowing for combining of the conversions. */
TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (type)
TYPE_PRECISION (TREE_TYPE (@0)) < TYPE_PRECISION (type)
/* The conversion check for being a nop can only be done at the gimple
level as fold_binary has some re-association code which can conflict
with this if there is a "constant" which is not a full INTEGER_CST. */
|| (GIMPLE && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))
/* It's also a good idea if the conversion is to a non-integer
mode. */
|| GET_MODE_CLASS (TYPE_MODE (type)) != MODE_INT

6
gcc/testsuite/gcc.c-torture/compile/pr103314-1.c Normal file
View file

@ -0,0 +1,6 @@
/* { dg-options "" } */
int main() {
int t = 1;
unsigned c = 0, d1 = t ? 1 ^ c ^ 1 >> (-1) : 0; /* { dg-warning "is negative" } */
return d1;
}