On Tue, 16 Oct 2012, Joern Rennecke wrote: > - Change the semantics of the HAVE_pattern macros for officially named > patterns so that they are defined as 0 when the pattern is not provided? > That choice would actually force people to change #ifdef into if (), > without the possibility of #if, where targets can have non-constant > pattern predicates.
I think that's appropriate. Note: for patterns that involve a machine mode, I think it's better to generate a macro (or function) that takes the mode as a parameter. This is because most references to modes such as SImode or DFmode in architecture-independent code are in principle dubious and would need to be eliminated for ports to unusual architectures with non-8-bit bytes (rather than being defined in architecture-independent code, it would be better to have a config/8-bit-byte-modes.def that's used by normal architectures but not by any future unusual ones). For example, if such macros / functions are generated automatically, c-family/c-cppbuiltin.c:mode_has_fma could cease to hardcode a list of four floating-point modes; instead, the caller could just call the new HAVE_ macro directly, with the mode as a parameter. > - We could have a header file that is maintained by hand, with a string > of #ifdef / #define / #endif . I think this is probably the simplest and so best approach - just list those patterns for which the HAVE_* is actually used. Or a text file with a list, indicating in some way the machine mode parameters to patterns for which those are relevant. -- Joseph S. Myers jos...@codesourcery.com
