I am currently testing the following patch to fix PR63175 - a regression
in expanding realign-load expressions the vectorizer generates.
get_object_alignment_2 gets MEM[&MEM[ptr + 4] & -16] here and while
it extracts an alignment of 128 from the & -16 recursing on the
address &MEM[ptr + 4] gets it a misalign offset of 32 which it fails
to re-apply the masking to.
Bootstrap and regtest running on x86_64-unknown-linux-gnu, I'm also
trying a ppc64-linux bootstrap & regtest (the only target that
exercises that vectorizer path I think), but it'll take me some
while there because I have no baseline.
(still the bug is quite obvious)
Richard.
2015-02-26 Richard Biener <rguent...@suse.de>
PR middle-end/63175
* builtins.c (get_object_alignment_2): Make sure to re-apply
the ANDed mask after recursing to its operand gets us a new
misalignment bit position.
Index: gcc/builtins.c
===================================================================
*** gcc/builtins.c (revision 220959)
--- gcc/builtins.c (working copy)
*************** get_object_alignment_2 (tree exp, unsign
*** 359,371 ****
tree addr = TREE_OPERAND (exp, 0);
unsigned ptr_align;
unsigned HOST_WIDE_INT ptr_bitpos;
if (TREE_CODE (addr) == BIT_AND_EXPR
&& TREE_CODE (TREE_OPERAND (addr, 1)) == INTEGER_CST)
{
! align = (TREE_INT_CST_LOW (TREE_OPERAND (addr, 1))
! & -TREE_INT_CST_LOW (TREE_OPERAND (addr, 1)));
! align *= BITS_PER_UNIT;
addr = TREE_OPERAND (addr, 0);
}
--- 359,373 ----
tree addr = TREE_OPERAND (exp, 0);
unsigned ptr_align;
unsigned HOST_WIDE_INT ptr_bitpos;
+ unsigned HOST_WIDE_INT ptr_bitmask = ~0;
+ /* If the address is explicitely aligned, handle that. */
if (TREE_CODE (addr) == BIT_AND_EXPR
&& TREE_CODE (TREE_OPERAND (addr, 1)) == INTEGER_CST)
{
! ptr_bitmask = TREE_INT_CST_LOW (TREE_OPERAND (addr, 1));
! ptr_bitmask *= BITS_PER_UNIT;
! align = ptr_bitmask & -ptr_bitmask;
addr = TREE_OPERAND (addr, 0);
}
*************** get_object_alignment_2 (tree exp, unsign
*** 373,378 ****
--- 375,383 ----
= get_pointer_alignment_1 (addr, &ptr_align, &ptr_bitpos);
align = MAX (ptr_align, align);
+ /* Re-apply explicit alignment to the bitpos. */
+ ptr_bitpos &= ptr_bitmask;
+
/* The alignment of the pointer operand in a TARGET_MEM_REF
has to take the variable offset parts into account. */
if (TREE_CODE (exp) == TARGET_MEM_REF)
