9a9ac3b959
* harbour/doc/cmpopt.txt
* added information about ( "<alias>" )-> to <alias>-> compile time
optimization
* harbour/source/rtl/valtostr.c
! fixed GPF if hb_valToStr() is called without any parameters.
In such case RTE is generated.
* harbour/source/rtl/transfrm.c
! fixed GPF if transform() is called without any parameters, i.e.:
? &("transform")()
* harbour/source/vm/itemapi.c
! return "U" if hb_itemTypeStr() is called with NULL parameter
It fixed GPF when valtype() is called without any parameters, i.e.:
? &("valtype")()
NOTE: Compiler check number of parameters in some functions and
refuse to compile the code when it's wrong but such validation
does not work in macrocompiler or when function is called
indirectly like in above examples or using function symbols
so always write such functions to work with wrong number of
parameters.
190 lines
8.0 KiB
Plaintext
190 lines
8.0 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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CHR( <nConst> )
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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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ASC( <cConst> [ , ... ] )
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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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LEN( <cConst> | <aConst> | <hConst> )
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CTOD( <cConst> [ , ... } )
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DTOS( <dConst> ] )
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STOD( [ <cConst> ] )
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HB_STOD( [ <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_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 callculated 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 miningless 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 optiomization 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 disabled 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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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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