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Added some more documentation on the global optimizer

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ceriel 1987-04-03 13:14:37 +00:00
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util/ack/ack.1.X
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@ -122,6 +122,8 @@ List only the erroneous lines of each Pascal source program.
.IP \-v .IP \-v
Verbose. Verbose.
Print information while juggling with files. Print information while juggling with files.
.IP \-KR
Tell the C-compiler to conform to "Kernighan & Ritchie" C.
.SB preprocessing .SB preprocessing
.IP \-I\fIdir\fP .IP \-I\fIdir\fP
\&\`#include\' files whose names do not begin with \`/\' are \&\`#include\' files whose names do not begin with \`/\' are
@ -136,6 +138,10 @@ If no definition is given the \fIname\fP is defined as 1.
.IP \-U\fIname\fP .IP \-U\fIname\fP
Remove any initial definition of \fIname\fP, before Remove any initial definition of \fIname\fP, before
preprocessing. preprocessing.
.IP \-P
Don't generate line directives.
.IP \-C
Leave C-comments in.
.SB debugging .SB debugging
.IP \-p .IP \-p
This flag tells both the Pascal and C front ends to include This flag tells both the Pascal and C front ends to include
@ -149,6 +155,58 @@ to a string containing the name of the routine.
.IP \-Oopt1,opt2,... .IP \-Oopt1,opt2,...
Try to use the named optimizers, or, if no optimizers are given, Try to use the named optimizers, or, if no optimizers are given,
try using the peephole optimizer and a target optimizer. try using the peephole optimizer and a target optimizer.
For optimizer names, see the table at the end of this manual page.
For the global optimizer, the following flags indicate which
phases must be executed:
.RS
.IP \-IL
Inline substitution.
.IP \-CS
Commom subexpression elimination.
.IP \-SR
Strength reduction.
.IP \-UD
Use definition analysis.
.IP \-LV
Live variable analysis.
.IP \-SA
Register allocation.
.IP \-SP
Stack pollution.
.IP \-BO
Branch optimization.
.IP \-CJ
Cross jumping.
.IP \-s<num>
Give an indication to the IL phase, how much bigger the program may get.
The IL phase will not make the program bigger when given \-s0.
.RE
.IP ""
The default options are: -CJ -BO -SP.
.br
In principle, the optimization phases can be run in any order; a phase
may even be run more than once. However, the following rules must be obeyed:
.RS
.IP -
the Live Variable analysis phase (LV) must be run prior to the
Register Alloacation phase (SA), as SA uses information produced by LV.
.IP -
SA should be the last phase.
.RE
.IP ""
Also, the following may be of use:
.RS
.IP -
Inline Substitution (IL) may create new opportunities for most other phases,
so it should be run as early as possible.
.IP -
Use Definition analysis (UD) may introduce opportunities for LV.
.IP -
Strength Reduction (SR) may creaye opportunities for UD.
.RE
.IP ""
The global optimizer is a combiner, so, when using it, offer it all the source
files of your program. It may throw away definitions of unused routines.
.IP \-L .IP \-L
Disable the generation of code by the front ends to Disable the generation of code by the front ends to
record line number and source file name at run-time. record line number and source file name at run-time.