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[patch] Fix PR80929: Realistic PARALLEL cost in seq_cost.


this small addition improves costs of PARALLELs in
rtlanal.c:seq_cost().  Up to now, these costs are
assumed to be 1 which gives gross inexact costs for,
e.g. divmod which is represented as PARALLEL.

The patch just forwards cost computation to insn_rtx_cost
which uses the cost of the 1st SET (if any) and otherwise
assign costs of 1 insn.

Bootstrapped & regtested on x86_64.

Moreover, it fixed the division by constant on avr where
the problem popped up since PR79665.

Ok to install?


	PR middle-end/80929
	* rtlanal.c (seq_cost) [PARALLEL]: Get cost from insn_rtx_cost
	instead of assuming cost of 1.

Index: rtlanal.c
--- rtlanal.c	(revision 248745)
+++ rtlanal.c	(working copy)
@@ -5300,6 +5300,9 @@ seq_cost (const rtx_insn *seq, bool spee
       set = single_set (seq);
       if (set)
         cost += set_rtx_cost (set, speed);
+      else if (INSN_P (seq)
+	       && PARALLEL == GET_CODE (PATTERN (seq)))
+	cost += insn_rtx_cost (PATTERN (seq), speed);

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