Use std::bitset for SubtargetFeatures

Previously, subtarget features were a bitfield with the underlying type being uint64_t. 
Since several targets (X86 and ARM, in particular) have hit or were very close to hitting this bound, switching the features to use a bitset.

No functional change.

Differential Revision: http://reviews.llvm.org/D7065

llvm-svn: 229831

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/MC/MCSubtargetInfo.cpp b/llvm/lib/MC/MCSubtargetInfo.cpp
index ca3894b29d3..aed91c5cadf 100644
--- a/llvm/lib/MC/MCSubtargetInfo.cpp
+++ b/llvm/lib/MC/MCSubtargetInfo.cpp
@@ -63,14 +63,19 @@ MCSubtargetInfo::InitMCSubtargetInfo(StringRef TT, StringRef C, StringRef FS,
 
 /// ToggleFeature - Toggle a feature and returns the re-computed feature
 /// bits. This version does not change the implied bits.
-uint64_t MCSubtargetInfo::ToggleFeature(uint64_t FB) {
+FeatureBitset MCSubtargetInfo::ToggleFeature(uint64_t FB) {
+  FeatureBits.flip(FB);
+  return FeatureBits;
+}
+
+FeatureBitset MCSubtargetInfo::ToggleFeature(const FeatureBitset &FB) {
   FeatureBits ^= FB;
   return FeatureBits;
 }
 
 /// ToggleFeature - Toggle a feature and returns the re-computed feature
 /// bits. This version will also change all implied bits.
-uint64_t MCSubtargetInfo::ToggleFeature(StringRef FS) {
+FeatureBitset MCSubtargetInfo::ToggleFeature(StringRef FS) {
   SubtargetFeatures Features;
   FeatureBits = Features.ToggleFeature(FeatureBits, FS, ProcFeatures);
   return FeatureBits;