15b51bbe0a
* harbour/src/rdd/dbfcdx/dbfcdx1.c
+ enabled automatic template order setting in Harbour SIXCDX RDD using
the same method as SIX3 SIXCDX RDD seems to use: by checking leading
character of key expression for: "sxChar(", "sxDate(", "sxNum(" and
"sxLog("
Warning: This code is enabled only for SIXCDX RDD and DBFCDX was not
modified.
* disabled RTE in SIXCDX when key add/del operation are executed
for non custom indexes and
* do not add keys with different type to template indexes in SIXCDX
RDD for strict SIX3 compatibility.
* harbour/doc/cmpopt.txt
+ added information about missing in Clipper expression optimization
in LOCAL, PRIVATE and PUBLIC variable declaration. Clipper optimize
only expressions used in STATIC declarations.
209 lines
8.6 KiB
Plaintext
209 lines
8.6 KiB
Plaintext
/*
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* $Id$
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*/
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Przemyslaw Czerpak (druzus/at/priv.onet.pl)
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Harbour compile time optimizations.
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1. Function call optimization.
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Just like Clipper Harbour compiler can optimize few function calls if
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parameters are well known constant values. Here is the list of functions
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optimized at compile time:
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- Clipper compatible:
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AT( <cConst1>, <cConst2> ) // Clipper wrongly calculates
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// AT( "", <cConst> ) as 1
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ASC( <cConst> [ , ... ] )
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CHR( <nConst> )
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LEN( <cConst> | <aConst> | <hConst> ) // <hConst> is Harbour extension
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UPPER( <cConst> ) // <cConst> cannot contain characters different then
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[0-9A-Za-z ]
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- Harbour extension:
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INT( <nConst> )
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MIN( <xConst1>, <xConst2> ) // <xConstN> is N, D or L value
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MAX( <xConst1>, <xConst2> ) // <xConstN> is N, D or L value
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EMPTY( <aConst> | <hConst> | <cConst> | <bConst> |
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<nConst> | <dConst>| <lConst> | NIL )
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CTOD( "" [ , ... ] )
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DTOS( <dConst> ] )
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STOD( [ <cConst> ] )
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HB_STOD( [ <cConst> ] )
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HB_STOT( [ <cConst> ] )
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HB_BITNOT( <nConst> [, ... ] )
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HB_BITAND( <nConst1>, <nConst2> [, <nConstN> ] )
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HB_BITOR( <nConst1>, <nConst2> [, <nConstN> ] )
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HB_BITXOR( <nConst1>, <nConst2> [, <nConstN> ] )
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HB_BITTEST( <nConst1>, <nConst2> [, ... ] )
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HB_BITSET( <nConst1>, <nConst2> [, ... ] )
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HB_BITRESET( <nConst1>, <nConst2> [, ... ] )
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HB_BITSHIFT( <nConst1>, <nConst2> [, ... ] )
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- Harbour special functions:
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HB_I18N_GETTEXT_NOOP( <cConst1> [ , <cConst2> ] )
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HB_I18N_NGETTEXT_NOOP( <cConst1> | <acConst1> [ , <cConst2> ] )
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HB_I18N_GETTEXT_NOOP_*( <cConst1> [ , <cConst2> ] )
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HB_I18N_NGETTEXT_NOOP_*( <cConst1> | <acConst1> [ , <cConst2> ] )
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HB_MUTEXCREATE()
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2. Expresion optimization:
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Just like Clipper Harbour compiler can optimize some expresions if
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arguments are well known and can be calculated at compile time:
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- Clipper compatible:
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<nConst1> + <nConst2> => <nConst>
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<nConst1> + <dConst2> => <dConst>
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<dConst1> + <nConst2> => <dConst>
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<cConst1> + <cConst2> => <cConst>
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// In Clipper neither <cConst1> nor <cConst2>
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// can contain '&' character. Harbour checks
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// if concatenation can change existing valid
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// macro name or ignore '&' when -kM compiler
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// switch which disable macro substitution
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// is used
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<nConst1> - <nConst2> => <nConst>
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<dConst1> - <dConst2> => <dConst>
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<dConst1> - <nConst2> => <dConst>
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<cConst1> - <cConst2> => <cConst>
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// In Clipper neither <cConst1> nor <cConst2>
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// can contain '&' character. Harbour checks
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// if concatenation can change existing valid
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// macro name or ignore '&' when -kM compiler
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// switch which disable macro substitution
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// is used
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<nConst1> * <nConst2> => <nConst>
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<nConst1> / <nConst2> => <nConst> // Clipper optimize only integers
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<nConst1> % <nConst2> => <nConst>
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<cConst1> $ <cConst2> => <lConst>
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// Clipper wrongly calculates
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// "" $ <cConst> as .T.
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// In Clipper neither <cConst1> nor <cConst2>
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// can contain '&' character. Harbour checks
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// if after '&' is potentially valid macro
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// name or ignore '&' when -kM compiler switch
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// which disable macro substitution is used
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<lConst1> == <lConst2> => <lConst>
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<nConst1> == <nConst2> => <lConst>
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<dConst1> == <dConst2> => <lConst>
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<cConst1> == <cConst2> => <lConst>
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// In Clipper neither <cConst1> nor <cConst2>
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// can contain '&' character. Harbour checks
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// if after '&' is potentially valid macro
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// name or ignore '&' when -kM compiler switch
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// which disable macro substitution is used
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NIL == <xConst> => <lConst>
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<xConst> == NIL => <lConst>
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<lConst1> = <lConst2> => <lConst>
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<nConst1> = <nConst2> => <lConst>
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<dConst1> = <dConst2> => <lConst>
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NIL = <xConst> => <lConst>
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<xConst> = NIL => <lConst>
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"" = "" => .T.
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<lConst1> != <lConst2> => <lConst>
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<nConst1> != <nConst2> => <lConst>
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<dConst1> != <dConst2> => <lConst>
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NIL != <xConst> => <lConst>
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<xConst> != NIL => <lConst>
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"" != "" => .F.
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<lConst1> >= <lConst2> => <lConst>
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<nConst1> >= <nConst2> => <lConst>
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<dConst1> >= <dConst2> => <lConst>
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<lConst1> <= <lConst2> => <lConst>
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<nConst1> <= <nConst2> => <lConst>
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<dConst1> <= <dConst2> => <lConst>
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<lConst1> > <lConst2> => <lConst>
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<nConst1> > <nConst2> => <lConst>
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<dConst1> > <dConst2> => <lConst>
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<lConst1> < <lConst2> => <lConst>
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<nConst1> < <nConst2> => <lConst>
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<dConst1> < <dConst2> => <lConst>
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.NOT. .T. => .F.
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.NOT. .F. => .T.
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<lConst1> .AND. <lConst2> => <lConst>
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<lConst1> .OR. <lConst2> => <lConst>
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IIF( .T., <expr1>, <expr2> ) => <expr1>
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IIF( .F., <expr1>, <expr2> ) => <expr2>
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- optimizations which can be disabled by -z compiler switch
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.T. .AND. <expr> => <expr>
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<expr> .AND. .T. => <expr>
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.F. .OR. <expr> => <expr>
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<expr> .OR. .F. => <expr>
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.F. .AND. <expr> => .F.
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<expr> .AND. .F. => .F.
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.T. .OR. <expr> => .T.
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<expr> .OR. .T. => .T.
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- Harbour extension:
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<nConst1> ^ <nConst2> => <nConst>
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<aValue> [ <nConst> ] => <xArrayItem>
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( <expr> ) => <expr> // it allows to optimize
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// expresions like: 1+(2)
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- Harbour extensions which may disable RT errors in wrong expressions
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or can change used operators using basic math rules. Enabled by -ko
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compiler switch:
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.NOT. .NOT. <expr> => <expr>
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- - <expr> => <expr>
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<expr> + 0 => <expr>
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0 + <expr> => <expr>
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<expr> + "" => <expr>
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"" + <expr> => <expr>
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( "<alias>" )-> => <alias>->
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In cases when result is meaningless Harbour compiler can skip code
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for operation, i.e. for such line of .prg code:
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( <exp1> <op> <exp2> )
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where result of <op> operation is ignored Harbour reduces the code
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to:
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( <exp1>, <exp2> )
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In Clipper in some places optimization is not enabled, f.e. Clipper
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does not optimize <exp> in expressions like:
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<exp> : msg( ... )
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Unlike Clipper Harbour tries to optimize all expressions.
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If some code needs strict Clipper behavior then it can be forced by using
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-kc Harbour compiler switch. It disables Harbour extensions and enables
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replicating some Clipper bugs like optimizing "" $ <cConst> to .T. at
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compile time (at runtime and in macrocompiler it's always .F. in Clipper
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and Harbour).
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Expressions fully optimized to constant values at compile time can be used
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to intialize static variables, f.e.:
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static s_var := ( 1 + 2 / 3 )
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Clipper does not optimize expression used in LOCAL, PRIVATE and
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PUBLIC variables declarations but it optimize expressions for STATIC
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declarations. This code illustrates it:
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proc main()
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memvar v, p
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local l := "" $ ""
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static s := "" $ ""
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private v := "" $ ""
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public p := "" $ ""
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? l, s, v, p, "" $ ""
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return
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This behavior is not replicated in Harbour even if -kc switch is used
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and Harbour optimize expressions in all declarations.
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Harbour has additional optimization phase which operates on generated PCODE.
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It can also reduce expressions, joins jumps, removes death or meaningless
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code which can appear after all other optimizations and were not optimized
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by expression optimizer. It can also optimize readonly local variables
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keeping the QSelf() value. QSelf() is not real function call but very fast
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single PCODE often used in OOP code. Harbour can replace local variables
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keeping it by direct QSelf() usage.
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