[EABI] Add LLVM support for -meabi flag

"GCC requires the freestanding environment provide memcpy, memmove, memset
and memcmp": https://gcc.gnu.org/onlinedocs/gcc-5.2.0/gcc/Standards.html

Hence in GNUEABI targets LLVM should not convert 'memops' to their equivalent
'__aeabi_memops'. This convertion violates GCC contract.

The -meabi flag controls whether or not LLVM will modify 'memops' in GNUEABI
targets.

Without -meabi: use the triple default EABI.
With -meabi=default: use the triple default EABI.
With -meabi=gnu: use 'memops'.
With -meabi=4 or -meabi=5: use '__aeabi_memops'.
With -meabi set to an unknown value: same as -meabi=default.

Patch by Vinicius Tinti.

llvm-svn: 252462

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/docs/CommandGuide/llc.rst b/llvm/docs/CommandGuide/llc.rst
index 8d5c9ce8f8a..5094259f9f9 100644
--- a/llvm/docs/CommandGuide/llc.rst
+++ b/llvm/docs/CommandGuide/llc.rst
@@ -127,6 +127,12 @@ End-user Options
  implements an LLVM target.  This will permit the target name to be used with
  the :option:`-march` option so that code can be generated for that target.
 
+.. option:: -meabi=[default|gnu|4|5]
+
+ Specify which EABI version should conform to.  Valid EABI versions are *gnu*,
+ *4* and *5*.  Default value (*default*) depends on the triple.
+
+
 Tuning/Configuration Options
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~