[PPC64] Add support for the ICBT instruction on POWER8.

Patch by Kit Barton.

Support for the ICBT instruction is currently present, but limited to
embedded processors. This change adds a new FeatureICBT that can be used
to identify whether the ICBT instruction is available on a specific processor.

Two new tests are added:
 * Positive test to ensure the icbt instruction is present when using
-mcpu=pwr8
 * Negative test to ensure the icbt instruction is not generated when
using -mcpu=pwr7

Both test cases use the Prefetch opcode in LLVM. They are based on the
ppc64-prefetch.ll test case.

llvm-svn: 226033

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index d8ba1c71a0f..ab36e90eaac 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -122,6 +122,8 @@ void PPCSubtarget::initializeEnvironment() {
   DeprecatedMFTB = false;
   DeprecatedDST = false;
   HasLazyResolverStubs = false;
+  HasICBT = false;
+
 }
 
 void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {