diff options
| author | Tamar Christina <tamar.christina@arm.com> | 2022-08-04 16:37:25 +0100 |
|---|---|---|
| committer | Tamar Christina <tamar.christina@arm.com> | 2022-08-04 16:37:25 +0100 |
| commit | be58bf98e98bb431ed26ca8be84586075fe8be82 (patch) | |
| tree | ad4ec4fca41b13fde7fee492566f545b6672916a | |
| parent | c832ec4c3ec4853ad89ff3b0dbf6e9454e75e8cc (diff) | |
middle-end: Simplify subtract where both arguments are being bitwise inverted.
This adds a match.pd rule that drops the bitwwise nots when both arguments to a
subtract is inverted. i.e. for:
float g(float a, float b)
{
return ~(int)a - ~(int)b;
}
we instead generate
float g(float a, float b)
{
return (int)b - (int)a;
}
We already do a limited version of this from the fold_binary fold functions but
this makes a more general version in match.pd that applies more often.
gcc/ChangeLog:
* match.pd: New bit_not rule.
gcc/testsuite/ChangeLog:
* gcc.dg/subnot.c: New test.
| -rw-r--r-- | gcc/match.pd | 5 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/subnot.c | 9 |
2 files changed, 14 insertions, 0 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index d3d73e3f55c..f82f94ad1fe 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -1308,6 +1308,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (simplify (bit_not (plus:c (bit_not @0) @1)) (minus @0 @1)) +/* (~X - ~Y) -> Y - X. */ +(simplify + (minus (bit_not @0) (bit_not @1)) + (with { tree utype = unsigned_type_for (type); } + (convert (minus (convert:utype @1) (convert:utype @0))))) /* ~(X - Y) -> ~X + Y. */ (simplify diff --git a/gcc/testsuite/gcc.dg/subnot.c b/gcc/testsuite/gcc.dg/subnot.c new file mode 100644 index 00000000000..d621bacd27b --- /dev/null +++ b/gcc/testsuite/gcc.dg/subnot.c @@ -0,0 +1,9 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-optimized" } */ + +float g(float a, float b) +{ + return ~(int)a - ~(int)b; +} + +/* { dg-final { scan-tree-dump-not "~" "optimized" } } */ |