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partial fix for 18008
- From: Richard Henderson <rth at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 26 Jan 2005 12:31:55 -0800
- Subject: partial fix for 18008
Allows combine to simplify
(set (zero_extract (reg:si 101) (const_int 2) (const_int 0))
(and:si (reg:102) (const_int 3)))
which, with no other changes, is what the testcase in this pr feeds
to combine on powerpc.
Bootstrapped and tested on powerpc-linux.
r~
* combine.c (make_field_assignment): Simplify store to zero_extract
from a source with an overlapping mask.
Index: combine.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/combine.c,v
retrieving revision 1.471
diff -u -p -r1.471 combine.c
--- combine.c 23 Jan 2005 15:43:56 -0000 1.471
+++ combine.c 26 Jan 2005 20:27:37 -0000
@@ -7815,14 +7815,14 @@ make_field_assignment (rtx x)
return x;
}
- else if (GET_CODE (src) == AND && GET_CODE (XEXP (src, 0)) == SUBREG
- && subreg_lowpart_p (XEXP (src, 0))
- && (GET_MODE_SIZE (GET_MODE (XEXP (src, 0)))
- < GET_MODE_SIZE (GET_MODE (SUBREG_REG (XEXP (src, 0)))))
- && GET_CODE (SUBREG_REG (XEXP (src, 0))) == ROTATE
- && GET_CODE (XEXP (SUBREG_REG (XEXP (src, 0)), 0)) == CONST_INT
- && INTVAL (XEXP (SUBREG_REG (XEXP (src, 0)), 0)) == -2
- && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
+ if (GET_CODE (src) == AND && GET_CODE (XEXP (src, 0)) == SUBREG
+ && subreg_lowpart_p (XEXP (src, 0))
+ && (GET_MODE_SIZE (GET_MODE (XEXP (src, 0)))
+ < GET_MODE_SIZE (GET_MODE (SUBREG_REG (XEXP (src, 0)))))
+ && GET_CODE (SUBREG_REG (XEXP (src, 0))) == ROTATE
+ && GET_CODE (XEXP (SUBREG_REG (XEXP (src, 0)), 0)) == CONST_INT
+ && INTVAL (XEXP (SUBREG_REG (XEXP (src, 0)), 0)) == -2
+ && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
{
assign = make_extraction (VOIDmode, dest, 0,
XEXP (SUBREG_REG (XEXP (src, 0)), 1),
@@ -7834,9 +7834,9 @@ make_field_assignment (rtx x)
/* If SRC is (ior (ashift (const_int 1) POS) DEST), this is a set of a
one-bit field. */
- else if (GET_CODE (src) == IOR && GET_CODE (XEXP (src, 0)) == ASHIFT
- && XEXP (XEXP (src, 0), 0) == const1_rtx
- && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
+ if (GET_CODE (src) == IOR && GET_CODE (XEXP (src, 0)) == ASHIFT
+ && XEXP (XEXP (src, 0), 0) == const1_rtx
+ && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
{
assign = make_extraction (VOIDmode, dest, 0, XEXP (XEXP (src, 0), 1),
1, 1, 1, 0);
@@ -7845,6 +7845,37 @@ make_field_assignment (rtx x)
return x;
}
+ /* If DEST is already a field assignment, i.e. ZERO_EXTRACT, and the
+ SRC is an AND with all bits of that field set, then we can discard
+ the AND. */
+ if (GET_CODE (dest) == ZERO_EXTRACT
+ && GET_CODE (XEXP (dest, 1)) == CONST_INT
+ && GET_CODE (src) == AND
+ && GET_CODE (XEXP (src, 1)) == CONST_INT)
+ {
+ HOST_WIDE_INT width = INTVAL (XEXP (dest, 1));
+ unsigned HOST_WIDE_INT and_mask = INTVAL (XEXP (src, 1));
+ unsigned HOST_WIDE_INT ze_mask;
+
+ if (width >= HOST_BITS_PER_WIDE_INT)
+ ze_mask = -1;
+ else
+ ze_mask = ((unsigned HOST_WIDE_INT)1 << width) - 1;
+
+ /* Complete overlap. We can remove the source AND. */
+ if ((and_mask & ze_mask) == ze_mask)
+ return gen_rtx_SET (VOIDmode, dest, XEXP (src, 0));
+
+ /* Partial overlap. We can reduce the source AND. */
+ if ((and_mask & ze_mask) != and_mask)
+ {
+ mode = GET_MODE (src);
+ src = gen_rtx_AND (mode, XEXP (src, 0),
+ gen_int_mode (mode, and_mask & ze_mask));
+ return gen_rtx_SET (VOIDmode, dest, src);
+ }
+ }
+
/* The other case we handle is assignments into a constant-position
field. They look like (ior/xor (and DEST C1) OTHER). If C1 represents
a mask that has all one bits except for a group of zero bits and