The following adjusts the find_base_{term,value} heuristic when
looking through ANDs to the case where it is obviously not
aligning a base (when the LSB is set).
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2019-11-18 Richard Biener <rguent...@suse.de>
PR rtl-optimization/92462
* alias.c (find_base_term): Restrict the look through ANDs.
(find_base_value): Likewise.
Index: gcc/alias.c
===================================================================
--- gcc/alias.c (revision 278293)
+++ gcc/alias.c (working copy)
@@ -1464,9 +1464,11 @@ find_base_value (rtx src)
return find_base_value (XEXP (src, 1));
case AND:
- /* If the second operand is constant set the base
- address to the first operand. */
- if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0)
+ /* Look through aligning ANDs. And AND with zero or one with
+ the LSB set isn't one (see for example PR92462). */
+ if (CONST_INT_P (XEXP (src, 1))
+ && INTVAL (XEXP (src, 1)) != 0
+ && (INTVAL (XEXP (src, 1)) & 1) == 0)
return find_base_value (XEXP (src, 0));
return 0;
@@ -2024,7 +2026,11 @@ find_base_term (rtx x, vec<std::pair<cse
}
case AND:
- if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0)
+ /* Look through aligning ANDs. And AND with zero or one with
+ the LSB set isn't one (see for example PR92462). */
+ if (CONST_INT_P (XEXP (x, 1))
+ && INTVAL (XEXP (x, 1)) != 0
+ && (INTVAL (XEXP (x, 1)) & 1) == 0)
return find_base_term (XEXP (x, 0), visited_vals);
return 0;
