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Re: [RFC] Add a new argument to SELECT_CC_MODE
> Maybe we can explicitly detect the nested COMPARE pattern in order to
> preserve the inner mode if nothing else changed.
Like in the attached patch.
--
Eric Botcazou
Index: combine.c
===================================================================
--- combine.c (revision 169914)
+++ combine.c (working copy)
@@ -6242,10 +6242,18 @@ simplify_set (rtx x)
enum rtx_code new_code;
rtx op0, op1, tmp;
int other_changed = 0;
+ rtx inner_compare = NULL_RTX;
enum machine_mode compare_mode = GET_MODE (dest);
if (GET_CODE (src) == COMPARE)
- op0 = XEXP (src, 0), op1 = XEXP (src, 1);
+ {
+ op0 = XEXP (src, 0), op1 = XEXP (src, 1);
+ if (GET_CODE (op0) == COMPARE && op1 == const0_rtx)
+ {
+ inner_compare = op0;
+ op0 = XEXP (inner_compare, 0), op1 = XEXP (inner_compare, 1);
+ }
+ }
else
op0 = src, op1 = CONST0_RTX (GET_MODE (src));
@@ -6287,6 +6295,12 @@ simplify_set (rtx x)
need to use a different CC mode here. */
if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC)
compare_mode = GET_MODE (op0);
+ else if (inner_compare
+ && GET_MODE_CLASS (GET_MODE (inner_compare)) == MODE_CC
+ && new_code == old_code
+ && op0 == XEXP (inner_compare, 0)
+ && op1 == XEXP (inner_compare, 1))
+ compare_mode = GET_MODE (inner_compare);
else
compare_mode = SELECT_CC_MODE (new_code, op0, op1);