[PATCH] [compiler-rt][builtins][MIPS] Add mips16 wrappers for float arithmetic, comparison and conversion

[Faraz Shahbazker]

================
Comment at: lib/builtins/mips/mips16_gen.h:22-23
@@ +21,4 @@
+
+#if defined(__mips_micromips) || defined(__mips_soft_float) \
+    || __mips_isa_rev >= 6
+  /* DO NOTHING */
----------------
Faraz Shahbazker wrote:
> Daniel Sanders wrote:
> > This doesn't look right to me. Why not test using '#if !defined(__mips16) || defined(__mips_soft_float)'?
> > 
> > Also, I think it's easier to understand if the content of mips16_*.c is wrapped in an '#if defined(__mips16)' rather than defining a macro to expand to nothing.
> Agreed on both counts.
After deeper inspection, using defined(mips16) is not suitable, because the library does not always need to be built in mips16 mode. The check is based on:
1. if an application built with -mips16 can link with _this_ library. For example, if the library uses micromips or an ABI other than o32/o64, then a mips16 application will fail to link with it. I need to add a check for ABI.
2. if the function needs to be defined. For example, all soft-fp wrappers are by definition redundant in soft-float mode as the compiler will never generate calls to those wrappers. Similarly, double-precision wrappers are redundant when building with -msingle-float -- this check needs to be added as well.

I could get rid of the empty-macros by conditionally #defining MIPS16_COMPAT in mips16_gen.h and wrapping contents of mips16_*.c in #ifdef MIPS16_COMPAT. Will include this and other changes in the next revision.

http://reviews.llvm.org/D4454