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| -rw-r--r-- | doc/ghdl.texi | 105 |
1 files changed, 31 insertions, 74 deletions
diff --git a/doc/ghdl.texi b/doc/ghdl.texi index fe0fda7..36df245 100644 --- a/doc/ghdl.texi +++ b/doc/ghdl.texi @@ -874,6 +874,31 @@ good feature, because it breaks the encapsulation rule. When set, an operator can be silently overridden in another package. You'd better to fix your design and use the @samp{numeric_std} package. +@item -frelaxed-rules +@cindex @option{-frelaxed-rules} switch +Within an object declaration, allow to reference the name (which +references the hidden declaration). This ignores the error in the +following code: + +@example +package pkg1 is + type state is (state1, state2, state3); +end pkg1; + +use work.pkg1.all; +package pkg2 is + constant state1 : state := state1; +end pkg2; +@end example + +Some code (such as Xilinx packages) have such constructs, which +are valid. + +(The scope of the @samp{state1} constant start at the @code{constant} +word. Because the constant @samp{state1} and the enumeration literal +@samp{state1} are homograph, the enumeration literal is hidden in the +immediate scope of the constant). + @item -fpsl @cindex @option{-fpsl} switch Enable parsing of PSL assertions within comments. @xref{PSL implementation}, @@ -1546,38 +1571,8 @@ end good; @cindex Math_Complex The @samp{ieee} math packages (@samp{math_real} and -@samp{math_complex}) provided with @code{GHDL} are not fully compliant with -the @code{IEEE} standard. They are based on an early draft which can be -redistributed contrary to the final version of the package. - -This is unfortunate and may generate errors as some declarations are missing -or have slightly changed. - -If you have bought the standard from @samp{ieee} then you can download -the sources of the packages from -@url{http://standards.ieee.org/downloads/1076/1076.2-1996} -(unrestricted access). You'd better to just download -@file{math_real.vhdl}, @file{math_real-body.vhdl}, -@file{math_complex.vhdl} and @file{math_complex-body.vhdl}. The other files -are not necessary: the @samp{std_logic_1164} package has to be updated for -@code{VHDL} 1993 (the @code{xnor} functions are commented out). - -If you want to replace math packages for the standard version of the -@code{ieee} library, do: -@smallexample -$ cp math_real.vhdl math_real-body.vhdl @file{ieee_install_dir} -$ cp math_complex.vhdl math_complex-body.vhdl @file{ieee_install_dir} -$ cd @file{ieee_install_dir} -$ ghdl -a --work=ieee math_real.vhdl math_real-body.vhdl -$ ghdl -a --work=ieee math_complex.vhdl math_complex-body.vhdl -@end smallexample -(Replace @file{ieee_install_dir} by the location of the @code{ieee} library as -displayed by @samp{ghdl -dispconfig}). - -You can repeat this for the @samp{synopsys} version of the @code{ieee} library. - -Don't forget that the math packages are only defined for the 1993 standard. - +@samp{math_complex}) provided with @code{GHDL} are fully compliant with +the @code{IEEE} standard. @node Simulation and runtime, GHDL implementation of VHDL, Invoking GHDL, Top @comment node-name, next, previous, up @@ -1843,7 +1838,6 @@ This chapter describes several implementation defined aspect of VHDL in GHDL. * VHDL files format:: * Top entity:: * Using vendor libraries:: -* Using ieee.math_real or ieee.math_complex:: * Interfacing to other languages:: @end menu @@ -2070,7 +2064,7 @@ default value; The ports type must be constrained. @end itemize -@node Using vendor libraries, Using ieee.math_real or ieee.math_complex, Top entity, GHDL implementation of VHDL +@node Using vendor libraries, Interfacing to other languages, Top entity, GHDL implementation of VHDL @comment node-name, next, previous, up @section Using vendor libraries Many vendors libraries have been analyzed with GHDL. There are @@ -2079,47 +2073,10 @@ However, some problems have been encountered. GHDL follows the VHDL LRM (the manual which defines VHDL) more strictly than other VHDL tools. You could try to relax the -restrictions by using the @option{--std=93c}, @option{-fexplicit} and -@option{--warn-no-vital-generic}. - -Even with these relaxations, some broken libraries may fail. - -For example, @code{unisim_VITAL.vhd} from @code{Xilinx} can't be -compiled because lines such as: -@smallexample - variable Write_A_Write_B : memory_collision_type := Write_A_Write_B; - variable Read_A_Write_B : memory_collision_type := Read_A_Write_B; -@end smallexample -(there are 6 such lines). -According to VHDL visibility rules, @samp{Write_A_Write_B} cannot be used -while it is defined. This is very logical because it prevents from silly -declarations such as -@smallexample - constant k : natural := 2 * k; -@end smallexample -This files must be modified. Fortunately, in the example the variables -are never written. So it is enough to remove them. - -@node Using ieee.math_real or ieee.math_complex, Interfacing to other languages, Using vendor libraries, GHDL implementation of VHDL -@comment node-name, next, previous, up -@section Using ieee.math_real or ieee.math_complex -@cindex math_real -@cindex math_complex -Contrary to other @samp{ieee} libraries, the math packages sources are not -freely available. The sources provided with GHDL are based on an early draft -and use the C libraries. As a consequence, you should link your design -with the @samp{libm.a} library using the @option{-Wl,} option like: -@smallexample -$ ghdl -e -Wl,-lm my_design -@end smallexample -Please, refer to your system manual for more details. - -Please also note that the @samp{ieee} libraries are not the same as the drafts. - -If you really need the @samp{ieee} math libraries, they are available on the -web, but they cannot be included in GHDL. +restrictions by using the @option{--std=93c}, @option{-fexplicit}, +@option{-frelaxed-rules} and @option{--warn-no-vital-generic}. -@node Interfacing to other languages, , Using ieee.math_real or ieee.math_complex, GHDL implementation of VHDL +@node Interfacing to other languages, , Using vendor libraries, GHDL implementation of VHDL @comment node-name, next, previous, up @section Interfacing to other languages @cindex interfacing |