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| author | Dominik Vogt <vogt@linux.vnet.ibm.com> | 2016-12-19 09:51:11 +0000 |
|---|---|---|
| committer | Andreas Krebbel <krebbel@gcc.gnu.org> | 2016-12-19 09:51:11 +0000 |
| commit | e01f223f28d94ececee29b8048434361de5cd40c (patch) | |
| tree | bcc6a4b4ea47d1b3d32ba5e04c14b62d3133c06c /gcc/combine.c | |
| parent | 26b14bc192861450d7d4d20faa5e54f489af1b68 (diff) | |
| download | gcc-e01f223f28d94ececee29b8048434361de5cd40c.zip gcc-e01f223f28d94ececee29b8048434361de5cd40c.tar.gz gcc-e01f223f28d94ececee29b8048434361de5cd40c.tar.bz2 | |
combine: Omit redundant AND in change_zero_ext.
This is another micro-optimisation in change_zero_ext. If an
(and (lshiftrt ... (N)) (M))
generated by change_zero_ext is equivalent to just
(lshiftrt ... (N))
(because the AND constant selects the N rightmost bits of the
result), strip off the AND.
gcc/ChangeLog:
2016-12-19 Dominik Vogt <vogt@linux.vnet.ibm.com>
* combine.c (change_zero_ext): Skip generation of redundant AND.
From-SVN: r243792
Diffstat (limited to 'gcc/combine.c')
| -rw-r--r-- | gcc/combine.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/gcc/combine.c b/gcc/combine.c index 473ffc4..e74ff4c 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -11289,8 +11289,13 @@ change_zero_ext (rtx pat) else continue; - wide_int mask = wi::mask (size, false, GET_MODE_PRECISION (mode)); - x = gen_rtx_AND (mode, x, immed_wide_int_const (mask, mode)); + if (!(GET_CODE (x) == LSHIFTRT + && CONST_INT_P (XEXP (x, 1)) + && size + INTVAL (XEXP (x, 1)) == GET_MODE_PRECISION (mode))) + { + wide_int mask = wi::mask (size, false, GET_MODE_PRECISION (mode)); + x = gen_rtx_AND (mode, x, immed_wide_int_const (mask, mode)); + } SUBST (**iter, x); changed = true; |