[globalisel][tablegen] Compute available feature bits correctly.

Summary:
Predicate<> now has a field to indicate how often it must be recomputed.
Currently, there are two frequencies, per-module (RecomputePerFunction==0)
and per-function (RecomputePerFunction==1). Per-function predicates are
currently recomputed more frequently than necessary since the only predicate
in this category is cheap to test. Per-module predicates are now computed in
getSubtargetImpl() while per-function predicates are computed in selectImpl().

Tablegen now manages the PredicateBitset internally. It should only be
necessary to add the required includes.

Also fixed a problem revealed by the test case where
constrainSelectedInstRegOperands() would attempt to tie operands that
BuildMI had already tied.

Reviewers: ab, qcolombet, t.p.northover, rovka, aditya_nandakumar

Reviewed By: rovka

Subscribers: kristof.beyls, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D32491

llvm-svn: 301750
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 82e9c5a..ce40120 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -314,8 +314,8 @@
 // AArch64 Instruction Predicate Definitions.
 def IsDarwin  : Predicate<"Subtarget->isTargetDarwin()">;
 def IsNotDarwin: Predicate<"!Subtarget->isTargetDarwin()">;
-def ForCodeSize   : Predicate<"ForCodeSize">;
-def NotForCodeSize   : Predicate<"!ForCodeSize">;
+def ForCodeSize   : Predicate<"Subtarget->getForCodeSize()">;
+def NotForCodeSize   : Predicate<"!Subtarget->getForCodeSize()">;
 
 include "AArch64InstrFormats.td"
 
diff --git a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
index b0e0e3e..9bfd570 100644
--- a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -51,7 +51,6 @@
                              const AArch64Subtarget &STI,
                              const AArch64RegisterBankInfo &RBI);
 
-  void beginFunction(const MachineFunction &MF) override;
   bool select(MachineInstr &I) const override;
 
 private:
@@ -74,12 +73,10 @@
   const AArch64InstrInfo &TII;
   const AArch64RegisterInfo &TRI;
   const AArch64RegisterBankInfo &RBI;
-  bool ForCodeSize;
 
-  PredicateBitset AvailableFeatures;
-  PredicateBitset
-  computeAvailableFeatures(const MachineFunction *MF,
-                           const AArch64Subtarget *Subtarget) const;
+#define GET_GLOBALISEL_PREDICATES_DECL
+#include "AArch64GenGlobalISel.inc"
+#undef GET_GLOBALISEL_PREDICATES_DECL
 
 // We declare the temporaries used by selectImpl() in the class to minimize the
 // cost of constructing placeholder values.
@@ -98,7 +95,10 @@
     const AArch64TargetMachine &TM, const AArch64Subtarget &STI,
     const AArch64RegisterBankInfo &RBI)
     : InstructionSelector(), TM(TM), STI(STI), TII(*STI.getInstrInfo()),
-      TRI(*STI.getRegisterInfo()), RBI(RBI), ForCodeSize(), AvailableFeatures()
+      TRI(*STI.getRegisterInfo()), RBI(RBI),
+#define GET_GLOBALISEL_PREDICATES_INIT
+#include "AArch64GenGlobalISel.inc"
+#undef GET_GLOBALISEL_PREDICATES_INIT
 #define GET_GLOBALISEL_TEMPORARIES_INIT
 #include "AArch64GenGlobalISel.inc"
 #undef GET_GLOBALISEL_TEMPORARIES_INIT
@@ -577,12 +577,6 @@
   return true;
 }
 
-void AArch64InstructionSelector::beginFunction(
-    const MachineFunction &MF) {
-  ForCodeSize = MF.getFunction()->optForSize();
-  AvailableFeatures = computeAvailableFeatures(&MF, &STI);
-}
-
 bool AArch64InstructionSelector::select(MachineInstr &I) const {
   assert(I.getParent() && "Instruction should be in a basic block!");
   assert(I.getParent()->getParent() && "Instruction should be in a function!");
diff --git a/llvm/lib/Target/AArch64/AArch64Subtarget.cpp b/llvm/lib/Target/AArch64/AArch64Subtarget.cpp
index 042755b..287fbc5 100644
--- a/llvm/lib/Target/AArch64/AArch64Subtarget.cpp
+++ b/llvm/lib/Target/AArch64/AArch64Subtarget.cpp
@@ -113,11 +113,12 @@
 
 AArch64Subtarget::AArch64Subtarget(const Triple &TT, const std::string &CPU,
                                    const std::string &FS,
-                                   const TargetMachine &TM, bool LittleEndian)
+                                   const TargetMachine &TM, bool LittleEndian,
+                                   bool ForCodeSize)
     : AArch64GenSubtargetInfo(TT, CPU, FS), ReserveX18(TT.isOSDarwin()),
       IsLittle(LittleEndian), TargetTriple(TT), FrameLowering(),
       InstrInfo(initializeSubtargetDependencies(FS, CPU)), TSInfo(),
-      TLInfo(TM, *this), GISel() {}
+      TLInfo(TM, *this), GISel(), ForCodeSize(ForCodeSize) {}
 
 const CallLowering *AArch64Subtarget::getCallLowering() const {
   assert(GISel && "Access to GlobalISel APIs not set");
diff --git a/llvm/lib/Target/AArch64/AArch64Subtarget.h b/llvm/lib/Target/AArch64/AArch64Subtarget.h
index 3d66a9e..5b9bee6 100644
--- a/llvm/lib/Target/AArch64/AArch64Subtarget.h
+++ b/llvm/lib/Target/AArch64/AArch64Subtarget.h
@@ -124,6 +124,8 @@
   /// an optional library.
   std::unique_ptr<GISelAccessor> GISel;
 
+  bool ForCodeSize;
+
 private:
   /// initializeSubtargetDependencies - Initializes using CPUString and the
   /// passed in feature string so that we can use initializer lists for
@@ -139,7 +141,7 @@
   /// of the specified triple.
   AArch64Subtarget(const Triple &TT, const std::string &CPU,
                    const std::string &FS, const TargetMachine &TM,
-                   bool LittleEndian);
+                   bool LittleEndian, bool ForCodeSize);
 
   /// This object will take onwership of \p GISelAccessor.
   void setGISelAccessor(GISelAccessor &GISel) {
@@ -262,6 +264,8 @@
     }
   }
 
+  bool getForCodeSize() const { return ForCodeSize; }
+
   /// ParseSubtargetFeatures - Parses features string setting specified
   /// subtarget options.  Definition of function is auto generated by tblgen.
   void ParseSubtargetFeatures(StringRef CPU, StringRef FS);
diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index dcc51bf..79d7162 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -255,6 +255,7 @@
 AArch64TargetMachine::getSubtargetImpl(const Function &F) const {
   Attribute CPUAttr = F.getFnAttribute("target-cpu");
   Attribute FSAttr = F.getFnAttribute("target-features");
+  bool ForCodeSize = F.optForSize();
 
   std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
                         ? CPUAttr.getValueAsString().str()
@@ -262,15 +263,17 @@
   std::string FS = !FSAttr.hasAttribute(Attribute::None)
                        ? FSAttr.getValueAsString().str()
                        : TargetFS;
+  std::string ForCodeSizeStr =
+      std::string(ForCodeSize ? "+" : "-") + "forcodesize";
 
-  auto &I = SubtargetMap[CPU + FS];
+  auto &I = SubtargetMap[CPU + FS + ForCodeSizeStr];
   if (!I) {
     // This needs to be done before we create a new subtarget since any
     // creation will depend on the TM and the code generation flags on the
     // function that reside in TargetOptions.
     resetTargetOptions(F);
     I = llvm::make_unique<AArch64Subtarget>(TargetTriple, CPU, FS, *this,
-                                            isLittle);
+                                            isLittle, ForCodeSize);
 #ifndef LLVM_BUILD_GLOBAL_ISEL
     GISelAccessor *GISel = new GISelAccessor();
 #else