Hello!
As shown in the PR [1], RTX costs can reject combination of the
operation and its embedded comparison. Attached patch fixes this by
ignoring the cost of embedded comparison.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65871#c10
2015-06-22 Uros Bizjak <ubiz...@gmail.com>
PR target/65871
* config/i386/i386.c (ix86_rtx_costs) <case COMPARE>: Ignore the
cost of embedded comparison.
Bootstrapped on x86_64-linux-gnu, regtest in progress.
Uros.
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 224718)
+++ config/i386/i386.c (working copy)
@@ -42531,6 +42531,12 @@ ix86_rtx_costs (rtx x, int code_i, int outer_code_
+ rtx_cost (const1_rtx, outer_code, opno, speed));
return true;
}
+
+ /* The embedded comparison operand is completely free. */
+ if (!general_operand (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
+ && XEXP (x, 1) == const0_rtx)
+ *total = 0;
+
return false;
case FLOAT_EXTEND:
