[Preprocessor] Implement __is_target_{arch|vendor|os|environment} function-like

Description

[Preprocessor] Implement __is_target_{arch|vendor|os|environment} function-like
builtin macros

This patch implements the is_target_arch, is_target_vendor, is_target_os,
and
is_target_environment Clang preprocessor extensions that were proposed by
@compnerd in Bob's cfe-dev post:
http://lists.llvm.org/pipermail/cfe-dev/2017-November/056166.html.

These macros can be used to examine the components of the target triple at
compile time. A has_builtin(is_target_???) preprocessor check can be used to
check for their availability.

__is_target_arch allows you to check if an arch is specified without worring
about a specific subarch, e.g.

is_target_arch(arm) returns 1 for the target arch "armv7"
is_target_arch(armv7) returns 1 for the target arch "armv7"
__is_target_arch(armv6) returns 0 for the target arch "armv7"

is_target_vendor and is_target_environment match the specific vendor
or environment. is_target_os matches the specific OS, but
is_target_os(darwin) will match any Darwin-based OS. "Unknown" can be used
to test if the triple's component is specified.

rdar://35753116

Differential Revision: https://reviews.llvm.org/D41087

Details

Committed
arphamanDec 14 2017, 11:22 AM
Differential Revision
D41087: [Preprocessor] Implement __is_target_{arch|vendor|os|environment} function-like builtin macros
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