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| author | Richard Biener <rguenther@suse.de> | 2015-09-14 09:25:16 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2015-09-14 09:25:16 +0000 |
| commit | 43f777061e5377597c125620b2749b2ad4bf2023 (patch) | |
| tree | 92a2ec35390efce941458e369c8114dd67d7192c | |
| parent | ed4c91ea5015e19d3ba11756d1179c2b52f0bd57 (diff) | |
| download | gcc-43f777061e5377597c125620b2749b2ad4bf2023.zip gcc-43f777061e5377597c125620b2749b2ad4bf2023.tar.gz gcc-43f777061e5377597c125620b2749b2ad4bf2023.tar.bz2 | |
match-and-simplify.texi: Fixup some formatting issues and document the 's' flag.
2015-09-14 Richard Biener <rguenther@suse.de>
* doc/match-and-simplify.texi: Fixup some formatting issues
and document the 's' flag.
From-SVN: r227739
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/match-and-simplify.texi | 26 |
2 files changed, 26 insertions, 5 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 5a8fa31..e347f03 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2015-09-14 Richard Biener <rguenther@suse.de> + + * doc/match-and-simplify.texi: Fixup some formatting issues + and document the 's' flag. + 2015-09-13 Olivier Hainque <hainque@adacore.com> Eric Botcazou <ebotcazou@adacore.com> diff --git a/gcc/doc/match-and-simplify.texi b/gcc/doc/match-and-simplify.texi index 876483f..2591ed8 100644 --- a/gcc/doc/match-and-simplify.texi +++ b/gcc/doc/match-and-simplify.texi @@ -186,20 +186,36 @@ preprocessor directives. (bit_and @@1 @@0)) @end smallexample -Here we introduce flags on match expressions. There is currently -a single flag, @code{c}, which denotes that the expression should +Here we introduce flags on match expressions. There used flag +above, @code{c}, denotes that the expression should be also matched commutated. Thus the above match expression is really the following four match expressions: +@smallexample (bit_and integral_op_p@@0 (bit_ior (bit_not @@0) @@1)) (bit_and (bit_ior (bit_not @@0) @@1) integral_op_p@@0) (bit_and integral_op_p@@0 (bit_ior @@1 (bit_not @@0))) (bit_and (bit_ior @@1 (bit_not @@0)) integral_op_p@@0) +@end smallexample Usual canonicalizations you know from GENERIC expressions are applied before matching, so for example constant operands always come second in commutative expressions. +The second supported flag is @code{s} which tells the code +generator to fail the pattern if the expression marked with +@code{s} does have more than one use. For example in + +@smallexample +(simplify + (pointer_plus (pointer_plus:s @@0 @@1) @@3) + (pointer_plus @@0 (plus @@1 @@3))) +@end smallexample + +this avoids the association if @code{(pointer_plus @@0 @@1)} is +used outside of the matched expression and thus it would stay +live and not trivially removed by dead code elimination. + More features exist to avoid too much repetition. @smallexample @@ -291,17 +307,17 @@ with a @code{?}: @smallexample (simplify - (eq (convert@@0 @@1) (convert? @@2)) + (eq (convert@@0 @@1) (convert@? @@2)) (eq @@1 (convert @@2))) @end smallexample which will match both @code{(eq (convert @@1) (convert @@2))} and @code{(eq (convert @@1) @@2)}. The optional converts are supposed to be all either present or not, thus -@code{(eq (convert? @@1) (convert? @@2))} will result in two +@code{(eq (convert@? @@1) (convert@? @@2))} will result in two patterns only. If you want to match all four combinations you have access to two additional conditional converts as in -@code{(eq (convert1? @@1) (convert2? @@2))}. +@code{(eq (convert1@? @@1) (convert2@? @@2))}. Predicates available from the GCC middle-end need to be made available explicitely via @code{define_predicates}: |