On Jun 20, 2012, Richard Guenther <richard.guent...@gmail.com> wrote:
> I have a question on the pre-existing condition > - if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1))) > xsize = -1; > so if this condition is not true then we simply strip off the AND of X and > do not adjust xsize at all? Likewise we do not adjust c? How can that > be conservatively correct? Yeah, xsize = -1 makes x “infinitely large”, so it will overlap if the RTXs are in any way related, or something like that. > Thus, I'd rather see > if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1))) > { > + HOST_WIDE_INT sc = INTVAL (XEXP (x, 1)); > + unsigned HOST_WIDE_INT uc = sc; > + if (xsize > 0 && sc < 0 && -uc == (uc & -uc)) > + { > + xsize -= sc + 1; > + c -= sc; > return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), > ysize, y, c); > } > } > as the sole supported case. Ack. Regstrapped successfully, checking this in.
for gcc/ChangeLog from Alexandre Oliva <aol...@redhat.com> PR debug/53671 PR debug/49888 * alias.c (memrefs_conflict_p): Improve handling of AND for alignment. Index: gcc/alias.c =================================================================== --- gcc/alias.c.orig 2012-06-21 15:05:48.144424495 -0300 +++ gcc/alias.c 2012-06-21 15:21:56.000000000 -0300 @@ -2097,25 +2097,32 @@ memrefs_conflict_p (int xsize, rtx x, in break; } - /* Treat an access through an AND (e.g. a subword access on an Alpha) - as an access with indeterminate size. Assume that references - besides AND are aligned, so if the size of the other reference is - at least as large as the alignment, assume no other overlap. */ + /* Deal with alignment ANDs by adjusting offset and size so as to + cover the maximum range, without taking any previously known + alignment into account. */ if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1))) { - if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1))) - xsize = -1; - return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c); + HOST_WIDE_INT sc = INTVAL (XEXP (x, 1)); + unsigned HOST_WIDE_INT uc = sc; + if (xsize > 0 && sc < 0 && -uc == (uc & -uc)) + { + xsize -= sc + 1; + c -= sc; + return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), + ysize, y, c); + } } if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1))) { - /* ??? If we are indexing far enough into the array/structure, we - may yet be able to determine that we can not overlap. But we - also need to that we are far enough from the end not to overlap - a following reference, so we do nothing with that for now. */ - if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1))) - ysize = -1; - return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c); + HOST_WIDE_INT sc = INTVAL (XEXP (y, 1)); + unsigned HOST_WIDE_INT uc = sc; + if (ysize > 0 && sc < 0 && -uc == (uc & -uc)) + { + ysize -= sc + 1; + c += sc; + return memrefs_conflict_p (xsize, x, + ysize, canon_rtx (XEXP (y, 0)), c); + } } if (CONSTANT_P (x))
-- Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/ You must be the change you wish to see in the world. -- Gandhi Be Free! -- http://FSFLA.org/ FSF Latin America board member Free Software Evangelist Red Hat Brazil Compiler Engineer