Revert "Use std::bitset for SubtargetFeatures"

This reverts commit r233055.

It still causes buildbot failures (gcc running out of memory on several platforms, and a self-host failure on arm), although less than the previous time.

llvm-svn: 233068

1 files changed, 10 insertions, 9 deletions

diff --git a/llvm/lib/Target/X86/Disassembler/X86Disassembler.cpp b/llvm/lib/Target/X86/Disassembler/X86Disassembler.cpp
index 46a6b3c8b2e..e8c547517b0 100644
--- a/llvm/lib/Target/X86/Disassembler/X86Disassembler.cpp
+++ b/llvm/lib/Target/X86/Disassembler/X86Disassembler.cpp
@@ -80,19 +80,20 @@ X86GenericDisassembler::X86GenericDisassembler(
                                          MCContext &Ctx,
                                          std::unique_ptr<const MCInstrInfo> MII)
   : MCDisassembler(STI, Ctx), MII(std::move(MII)) {
-  const FeatureBitset &FB = STI.getFeatureBits();
-  if (FB[X86::Mode16Bit]) {
+  switch (STI.getFeatureBits() &
+          (X86::Mode16Bit | X86::Mode32Bit | X86::Mode64Bit)) {
+  case X86::Mode16Bit:
     fMode = MODE_16BIT;
-    return;
-  } else if (FB[X86::Mode32Bit]) {
+    break;
+  case X86::Mode32Bit:
     fMode = MODE_32BIT;
-    return;
-  } else if (FB[X86::Mode64Bit]) {
+    break;
+  case X86::Mode64Bit:
     fMode = MODE_64BIT;
-    return;
+    break;
+  default:
+    llvm_unreachable("Invalid CPU mode");
   }
-
-  llvm_unreachable("Invalid CPU mode");
 }
 
 struct Region {