Use the 'target-features' and 'target-cpu' attributes to reset the subtarget features.

If two functions require different features (e.g., `-mno-sse' vs. `-msse') then
we want to honor that, especially during LTO. We can do that by resetting the
subtarget's features depending upon the 'target-feature' attribute.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175314 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetSubtargetInfo.h

@@ -19,6 +19,7 @@
 
 namespace llvm {
 
+class MachineFunction;
 class MachineInstr;
 class SDep;
 class SUnit;
@@ -73,6 +74,9 @@ public:
   // the latency of a schedule dependency.
   virtual void adjustSchedDependency(SUnit *def, SUnit *use,
                                      SDep& dep) const { }
+
+  /// \brief Reset the features for the subtarget.
+  virtual void resetSubtargetFeatures(const MachineFunction *MF) { }
 };
 
 } // End llvm namespace

lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -354,6 +354,10 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   TTI = getAnalysisIfAvailable<TargetTransformInfo>();
   GFI = Fn.hasGC() ? &getAnalysis<GCModuleInfo>().getFunctionInfo(Fn) : 0;
 
+  TargetSubtargetInfo &ST =
+    const_cast<TargetSubtargetInfo&>(TM.getSubtarget<TargetSubtargetInfo>());
+  ST.resetSubtargetFeatures(MF);
+
   DEBUG(dbgs() << "\n\n\n=== " << Fn.getName() << "\n");
 
   SplitCriticalSideEffectEdges(const_cast<Function&>(Fn), this);

lib/Target/X86/X86Subtarget.cpp

@@ -14,6 +14,8 @@
 #define DEBUG_TYPE "subtarget"
 #include "X86Subtarget.h"
 #include "X86InstrInfo.h"
+#include "llvm/IR/Attributes.h"
+#include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -324,46 +326,21 @@ void X86Subtarget::AutoDetectSubtargetFeatures() {
   }
 }
 
-X86Subtarget::X86Subtarget(const std::string &TT, const std::string &CPU,
+void X86Subtarget::resetSubtargetFeatures(const MachineFunction *MF) {
-                           const std::string &FS,
+  AttributeSet FnAttrs = MF->getFunction()->getAttributes();
-                           unsigned StackAlignOverride, bool is64Bit)
+  Attribute CPUAttr = FnAttrs.getAttribute(AttributeSet::FunctionIndex,
-  : X86GenSubtargetInfo(TT, CPU, FS)
+                                           "target-cpu");
-  , X86ProcFamily(Others)
+  Attribute FSAttr = FnAttrs.getAttribute(AttributeSet::FunctionIndex,
-  , PICStyle(PICStyles::None)
+                                          "target-features");
-  , X86SSELevel(NoMMXSSE)
+  std::string CPU =
-  , X863DNowLevel(NoThreeDNow)
+    !CPUAttr.hasAttribute(Attribute::None) ?CPUAttr.getValueAsString() : "";
-  , HasCMov(false)
+  std::string FS =
-  , HasX86_64(false)
+    !FSAttr.hasAttribute(Attribute::None) ? FSAttr.getValueAsString() : "";
-  , HasPOPCNT(false)
+  if (!FS.empty())
-  , HasSSE4A(false)
+    resetSubtargetFeatures(CPU, FS);
-  , HasAES(false)
+}
-  , HasPCLMUL(false)
+
-  , HasFMA(false)
+void X86Subtarget::resetSubtargetFeatures(StringRef CPU, StringRef FS) {
-  , HasFMA4(false)
-  , HasXOP(false)
-  , HasMOVBE(false)
-  , HasRDRAND(false)
-  , HasF16C(false)
-  , HasFSGSBase(false)
-  , HasLZCNT(false)
-  , HasBMI(false)
-  , HasBMI2(false)
-  , HasRTM(false)
-  , HasADX(false)
-  , IsBTMemSlow(false)
-  , IsUAMemFast(false)
-  , HasVectorUAMem(false)
-  , HasCmpxchg16b(false)
-  , UseLeaForSP(false)
-  , HasSlowDivide(false)
-  , PostRAScheduler(false)
-  , PadShortFunctions(false)
-  , stackAlignment(4)
-  // FIXME: this is a known good value for Yonah. How about others?
-  , MaxInlineSizeThreshold(128)
-  , TargetTriple(TT)
-  , In64BitMode(is64Bit) {
-  // Determine default and user specified characteristics
   std::string CPUName = CPU;
   if (!FS.empty() || !CPU.empty()) {
     if (CPUName.empty()) {
@@ -440,6 +417,49 @@ X86Subtarget::X86Subtarget(const std::string &TT, const std::string &CPU,
     stackAlignment = 16;
 }
 
+X86Subtarget::X86Subtarget(const std::string &TT, const std::string &CPU,
+                           const std::string &FS,
+                           unsigned StackAlignOverride, bool is64Bit)
+  : X86GenSubtargetInfo(TT, CPU, FS)
+  , X86ProcFamily(Others)
+  , PICStyle(PICStyles::None)
+  , X86SSELevel(NoMMXSSE)
+  , X863DNowLevel(NoThreeDNow)
+  , HasCMov(false)
+  , HasX86_64(false)
+  , HasPOPCNT(false)
+  , HasSSE4A(false)
+  , HasAES(false)
+  , HasPCLMUL(false)
+  , HasFMA(false)
+  , HasFMA4(false)
+  , HasXOP(false)
+  , HasMOVBE(false)
+  , HasRDRAND(false)
+  , HasF16C(false)
+  , HasFSGSBase(false)
+  , HasLZCNT(false)
+  , HasBMI(false)
+  , HasBMI2(false)
+  , HasRTM(false)
+  , HasADX(false)
+  , IsBTMemSlow(false)
+  , IsUAMemFast(false)
+  , HasVectorUAMem(false)
+  , HasCmpxchg16b(false)
+  , UseLeaForSP(false)
+  , HasSlowDivide(false)
+  , PostRAScheduler(false)
+  , PadShortFunctions(false)
+  , stackAlignment(4)
+  // FIXME: this is a known good value for Yonah. How about others?
+  , MaxInlineSizeThreshold(128)
+  , TargetTriple(TT)
+  , StackAlignOverride(StackAlignOverride)
+  , In64BitMode(is64Bit) {
+  resetSubtargetFeatures(CPU, FS);
+}
+
 bool X86Subtarget::enablePostRAScheduler(
            CodeGenOpt::Level OptLevel,
            TargetSubtargetInfo::AntiDepBreakMode& Mode,

lib/Target/X86/X86Subtarget.h

@@ -168,11 +168,13 @@ protected:
   InstrItineraryData InstrItins;
 
 private:
+  /// StackAlignOverride - Override the stack alignment.
+  unsigned StackAlignOverride;
+
   /// In64BitMode - True if compiling for 64-bit, false for 32-bit.
   bool In64BitMode;
 
 public:
-
   /// This constructor initializes the data members to match that
   /// of the specified triple.
   ///
@@ -197,6 +199,10 @@ public:
   /// instruction.
   void AutoDetectSubtargetFeatures();
 
+  /// \brief Reset the features for the X86 target.
+  virtual void resetSubtargetFeatures(const MachineFunction *MF);
+  void resetSubtargetFeatures(StringRef CPU, StringRef FS);
+
   /// Is this x86_64? (disregarding specific ABI / programming model)
   bool is64Bit() const {
     return In64BitMode;