Add runtime support for __cpu_model (__builtin_cpu_supports)

Summary:
This aims to add support for __cpu_model and address Bug 25510. It uses
the code from lib/Support/Host.cpp for cpu detection, and creates
__cpu_model with that info.

Tested on OSX, it builts successfully, but the current version does
*not* resolve Bug 25510. The __cpu_model symbol is present in the
library but it only gets loaded with -all_load. This patch will not land
until this issue is clarified.

Built on Linux as well (though libgcc is the default). The use of "asm"
required -std=gnu99, hence the cmake change. Corrections on better
addressing this are welcome.

Note: See additional comments on D20988 (committed as r271921).

Reviewers: llvm-commits, joerg, echristo, mehdi_amini

Subscribers: mehdi_amini

Differential revision: http://reviews.llvm.org/D21033

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@274873 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/test/builtins/Unit/cpu_model_test.c b/test/builtins/Unit/cpu_model_test.c
new file mode 100644
index 000000000..5a918bde7
--- /dev/null
+++ b/test/builtins/Unit/cpu_model_test.c
@@ -0,0 +1,19 @@
+//===-- cpu_model_test.c - Test __builtin_cpu_supports -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file tests __builtin_cpu_supports for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+int main (void) {
+  if(__builtin_cpu_supports("avx2"))
+    return 4;
+  else
+    return 3;
+}