===================================================================
@@ -2093,17 +2093,6 @@ base_alias_check (rtx x, rtx x_base, rtx y, rtx y_
if (rtx_equal_p (x_base, y_base))
return 1;
- if (GET_CODE (x_base) == SYMBOL_REF && GET_CODE (y_base) == SYMBOL_REF)
- {
- tree x_decl = SYMBOL_REF_DECL (x_base);
- tree y_decl = SYMBOL_REF_DECL (y_base);
-
- /* We can assume that no stores are made to labels. */
- if (!x_decl || !y_decl)
- return 0;
- return compare_base_decls (x_decl, y_decl) != 0;
- }
-
/* The base addresses are different expressions. If they are not accessed
via AND, there is no conflict. We can bring knowledge of object
alignment into play here. For example, on alpha, "char a, b;" can
@@ -2122,6 +2111,17 @@ base_alias_check (rtx x, rtx x_base, rtx y, rtx y_
|| (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
return 1;
+ if (GET_CODE (x_base) == SYMBOL_REF && GET_CODE (y_base) == SYMBOL_REF)
+ {
+ tree x_decl = SYMBOL_REF_DECL (x_base);
+ tree y_decl = SYMBOL_REF_DECL (y_base);
+
+ /* We can assume that no stores are made to labels. */
+ if (!x_decl || !y_decl)
+ return 0;
+ return compare_base_decls (x_decl, y_decl) != 0;
+ }
+
/* Differing symbols not accessed via AND never alias. */
if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
return 0;
@@ -2344,6 +2344,12 @@ memrefs_conflict_p (int xsize, rtx x, int ysize, r
/* If both decls are the same, decide by offsets. */
if (cmp == 1)
return offset_overlap_p (c, xsize, ysize);
+ /* Assume a potential overlap for symbolic addresses that went
+ through alignment adjustments (i.e., that have negative
+ sizes), because we can't know how far they are from each
+ other. */
+ if (xsize < 0 || ysize < 0)
+ return -1;
/* If decls are different or we know by offsets that there is no overlap,
we win. */
if (!cmp || !offset_overlap_p (c, xsize, ysize))
Hello! Attached patch returns "unknown" from memrefs_conflict_p when realigned decls are processed. This is the same approach as is done at the end of memrefs_conflict_p. We still need early return for AND addresses in base_alias_check. 2016-01-08 Uros Bizjak <ubizjak@gmail.com> PR middle-end/68999 * alias.c (memrefs_conflict_p): Return -1 for different decls that went through alignment adjustments. (base_alias_check): Move check for addresses with alignment ANDs before the call for compare_base_decls. Patch was bootstrapped and regression tested on x86_64-linux-gnu {,-m32} and alpha-linux-gnu native [2]. OK for mainline? Uros.