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tm.texi (TARGET_RTX_COSTS): Document that instruction costs should be based on code size when... 

* doc/tm.texi (TARGET_RTX_COSTS): Document that instruction
	costs should be based on code size when optimizing for size.

From-SVN: r82025
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Roger Sayle 2004-05-19 13:54:15 +00:00 committed by Roger Sayle
parent d28f752bd3
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2 changed files with 12 additions and 1 deletions
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@ -1,3 +1,8 @@
2004-05-19 Roger Sayle <roger@eyesopen.com>
* doc/tm.texi (TARGET_RTX_COSTS): Document that instruction
costs should be based on code size when optimizing for size.
2004-05-19 Paolo Bonzini <bonzini@gnu.org>
* fold-const.c: Remove non-printable character 160.

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gcc/doc/tm.texi
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@ -5456,7 +5456,13 @@ instructions.
On entry to the hook, @code{*@var{total}} contains a default estimate
for the cost of the expression. The hook should modify this value as
necessary.
necessary. Traditionally, the default costs are @code{COSTS_N_INSNS (5)}
for multiplications, @code{COSTS_N_INSNS (7)} for division and modulus
operations, and @code{COSTS_N_INSNS (1)} for all other operations.
When optimizing for code size, i.e@. when @code{optimize_size} is
non-zero, this target hook should be used to estimate the relative
size cost of an expression, again relative to @code{COSTS_N_INSNS}.
The hook returns true when all subexpressions of @var{x} have been
processed, and false when @code{rtx_cost} should recurse.