[llvm] r241961 - MC: Only allow changing feature bits in MCSubtargetInfo

[Duncan P. N. Exon Smith]

Author: dexonsmith
Date: Fri Jul 10 17:52:15 2015
New Revision: 241961

URL: http://llvm.org/viewvc/llvm-project?rev=241961&view=rev
Log:
MC: Only allow changing feature bits in MCSubtargetInfo

Disallow all mutation of `MCSubtargetInfo` expect the feature bits.

Besides deleting the assignment operators -- which were dead "code" --
this restricts `InitMCProcessorInfo()` to subclass initialization
sequences, and exposes a new more limited function called
`setDefaultFeatures()` for use by the ARMAsmParser `.cpu` directive.

There's a small functional change here: ARMAsmParser used to adjust
`MCSubtargetInfo::CPUSchedModel` as a side effect of calling
`InitMCProcessorInfo()`, but I've removed that suspicious behaviour.
Since the AsmParser shouldn't be doing any scheduling, there shouldn't
be any observable change...

Modified:
    llvm/trunk/include/llvm/MC/MCSubtargetInfo.h
    llvm/trunk/lib/MC/MCSubtargetInfo.cpp
    llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp

Modified: llvm/trunk/include/llvm/MC/MCSubtargetInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSubtargetInfo.h?rev=241961&r1=241960&r2=241961&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCSubtargetInfo.h (original)
+++ llvm/trunk/include/llvm/MC/MCSubtargetInfo.h Fri Jul 10 17:52:15 2015
@@ -45,8 +45,11 @@ class MCSubtargetInfo {
   FeatureBitset FeatureBits;           // Feature bits for current CPU + FS
 
   MCSubtargetInfo() = delete;
+  MCSubtargetInfo &operator=(MCSubtargetInfo &&) = delete;
+  MCSubtargetInfo &operator=(const MCSubtargetInfo &) = delete;
 
 public:
+  MCSubtargetInfo(const MCSubtargetInfo &) = default;
   MCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS,
                   ArrayRef<SubtargetFeatureKV> PF,
                   ArrayRef<SubtargetFeatureKV> PD,
@@ -75,10 +78,17 @@ public:
     FeatureBits = FeatureBits_;
   }
 
-  /// InitMCProcessorInfo - Set or change the CPU (optionally supplemented with
-  /// feature string). Recompute feature bits and scheduling model.
+protected:
+  /// Initialize the scheduling model and feature bits.
+  ///
+  /// FIXME: Find a way to stick this in the constructor, since it should only
+  /// be called during initialization.
   void InitMCProcessorInfo(StringRef CPU, StringRef FS);
 
+public:
+  /// Set the features to the default for the given CPU.
+  void setDefaultFeatures(StringRef CPU);
+
   /// ToggleFeature - Toggle a feature and returns the re-computed feature
   /// bits. This version does not change the implied bits.
   FeatureBitset ToggleFeature(uint64_t FB);

Modified: llvm/trunk/lib/MC/MCSubtargetInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCSubtargetInfo.cpp?rev=241961&r1=241960&r2=241961&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCSubtargetInfo.cpp (original)
+++ llvm/trunk/lib/MC/MCSubtargetInfo.cpp Fri Jul 10 17:52:15 2015
@@ -17,18 +17,25 @@
 
 using namespace llvm;
 
-/// InitMCProcessorInfo - Set or change the CPU (optionally supplemented
-/// with feature string). Recompute feature bits and scheduling model.
-void
-MCSubtargetInfo::InitMCProcessorInfo(StringRef CPU, StringRef FS) {
+static FeatureBitset getFeatures(StringRef CPU, StringRef FS,
+                                 ArrayRef<SubtargetFeatureKV> ProcDesc,
+                                 ArrayRef<SubtargetFeatureKV> ProcFeatures) {
   SubtargetFeatures Features(FS);
-  FeatureBits = Features.getFeatureBits(CPU, ProcDesc, ProcFeatures);
+  return Features.getFeatureBits(CPU, ProcDesc, ProcFeatures);
+}
+
+void MCSubtargetInfo::InitMCProcessorInfo(StringRef CPU, StringRef FS) {
+  FeatureBits = getFeatures(CPU, FS, ProcDesc, ProcFeatures);
   if (!CPU.empty())
     CPUSchedModel = &getSchedModelForCPU(CPU);
   else
     CPUSchedModel = &MCSchedModel::GetDefaultSchedModel();
 }
 
+void MCSubtargetInfo::setDefaultFeatures(StringRef CPU) {
+  FeatureBits = getFeatures(CPU, "", ProcDesc, ProcFeatures);
+}
+
 MCSubtargetInfo::MCSubtargetInfo(
     const Triple &TT, StringRef C, StringRef FS,
     ArrayRef<SubtargetFeatureKV> PF, ArrayRef<SubtargetFeatureKV> PD,

Modified: llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp?rev=241961&r1=241960&r2=241961&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp (original)
+++ llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp Fri Jul 10 17:52:15 2015
@@ -9212,7 +9212,7 @@ bool ARMAsmParser::parseDirectiveCPU(SML
     return false;
   }
 
-  STI.InitMCProcessorInfo(CPU, "");
+  STI.setDefaultFeatures(CPU);
   setAvailableFeatures(ComputeAvailableFeatures(STI.getFeatureBits()));
 
   return false;