[PATCH] D57143: [builtins] Rounding mode support for addxf3/subxf3

Fri Jan 25 02:12:18 PST 2019

MaskRay added inline comments.

================
Comment at: compiler-rt/lib/builtins/arm/fp_mode.c:25
+  uint32_t fpscr;
+  __asm__ __volatile__("vmrs  %0, fpscr" : "=r" (fpscr));
+  fpscr = fpscr >> ARM_RMODE_SHIFT & ARM_RMODE_MASK;
----------------
efriedma wrote:
> This needs to be guarded; vmrs is only valid on targets which support VFP.  Not sure if we need to try to check that at runtime...
On ARM, perhaps we can assume only `FE_TONEAREST` is available.

https://github.com/gcc-mirror/gcc/blob/master/libgcc/config/arm/ieee754-sf.S

> Only the default rounding mode is intended for best performances.

Repository:
  rCRT Compiler Runtime

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57143/new/

https://reviews.llvm.org/D57143