mirror/gcc
2
0
Fork 0
mirror of git://gcc.gnu.org/git/gcc.git synced 2025-04-05 10:50:51 +08:00
Code Issues Packages Projects Releases Wiki Activity

combine: Omit redundant AND in change_zero_ext.

Browse Source 
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
This commit is contained in:
Dominik Vogt 2016-12-19 09:51:11 +00:00 committed by Andreas Krebbel
parent 26b14bc192
commit e01f223f28
2 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
gcc/ChangeLog
View File

@ -1,3 +1,7 @@
2016-12-19 Dominik Vogt <vogt@linux.vnet.ibm.com>
* combine.c (change_zero_ext): Skip generation of redundant AND.
2016-12-19 Krister Walfridsson <krister.walfridsson@gmail.com>
* config/netbsd.h (LINK_EH_SPEC): Define.

9
gcc/combine.c
View File

@ -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;