MC: Add MCInstrDesc::mayAffectControlFlow() method.

MC disassembler clients (LLDB) are interested in querying if an
instruction may affect control flow other than by virtue of being
an explicit branch instruction. For example, instructions which
write directly to the PC on some architectures.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170610 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCInstrDesc.h

@@ -16,6 +16,8 @@
 #define LLVM_MC_MCINSTRDESC_H
 
 #include "llvm/Support/DataTypes.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCInst.h"
 
 namespace llvm {
 
@@ -258,6 +260,17 @@ class MCInstrDesc {
     return isBranch() & isBarrier() & !isIndirectBranch();
   }
 
+  /// Return true if this is a branch or an instruction which directly
+  /// writes to the program counter. Considered 'may' affect rather than
+  /// 'does' affect as things like predication are not taken into account.
+  bool mayAffectControlFlow(const MCInst &MI, const MCRegisterInfo &RI) const {
+    if (isBranch() || isCall() || isReturn() || isIndirectBranch())
+      return true;
+    unsigned PC = RI.getProgramCounter();
+    if (PC == 0) return false;
+    return hasDefOfPhysReg(MI, PC, RI);
+  }
+
   /// isPredicable - Return true if this instruction has a predicate operand
   /// that controls execution. It may be set to 'always', or may be set to other
   /// values. There are various methods in TargetInstrInfo that can be used to
@@ -502,13 +515,26 @@ class MCInstrDesc {
 
   /// hasImplicitDefOfPhysReg - Return true if this instruction implicitly
   /// defines the specified physical register.
-  bool hasImplicitDefOfPhysReg(unsigned Reg) const {
+  bool hasImplicitDefOfPhysReg(unsigned Reg,
+                               const MCRegisterInfo *MRI = 0) const {
     if (const uint16_t *ImpDefs = ImplicitDefs)
       for (; *ImpDefs; ++ImpDefs)
-        if (*ImpDefs == Reg) return true;
+        if (*ImpDefs == Reg || (MRI && MRI->isSubRegister(Reg, *ImpDefs)))
+            return true;
     return false;
   }
 
+  /// Return true if this instruction defines the specified physical
+  /// register, either explicitly or implicitly.
+  bool hasDefOfPhysReg(const MCInst &MI, unsigned Reg,
+                       const MCRegisterInfo &RI) const {
+    for (int i = 0, e = NumDefs; i != e; ++i)
+      if (MI.getOperand(i).isReg() &&
+          RI.isSubRegisterEq(Reg, MI.getOperand(i).getReg()))
+        return true;
+    return hasImplicitDefOfPhysReg(Reg, &RI);
+  }
+
   /// getSchedClass - Return the scheduling class for this instruction.  The
   /// scheduling class is an index into the InstrItineraryData table.  This
   /// returns zero if there is no known scheduling information for the

include/llvm/MC/MCRegisterInfo.h

@@ -152,6 +152,7 @@ class MCRegisterInfo {
   const MCRegisterDesc *Desc;                 // Pointer to the descriptor array
   unsigned NumRegs;                           // Number of entries in the array
   unsigned RAReg;                             // Return address register
+  unsigned PCReg;                             // Program counter register
   const MCRegisterClass *Classes;             // Pointer to the regclass array
   unsigned NumClasses;                        // Number of entries in the array
   unsigned NumRegUnits;                       // Number of regunits.
@@ -232,6 +233,7 @@ class MCRegisterInfo {
   /// InitMCRegisterInfo - Initialize MCRegisterInfo, called by TableGen
   /// auto-generated routines. *DO NOT USE*.
   void InitMCRegisterInfo(const MCRegisterDesc *D, unsigned NR, unsigned RA,
+                          unsigned PC,
                           const MCRegisterClass *C, unsigned NC,
                           const uint16_t (*RURoots)[2],
                           unsigned NRU,
@@ -243,6 +245,7 @@ class MCRegisterInfo {
     Desc = D;
     NumRegs = NR;
     RAReg = RA;
+    PCReg = PC;
     Classes = C;
     DiffLists = DL;
     RegStrings = Strings;
@@ -297,6 +300,11 @@ class MCRegisterInfo {
     return RAReg;
   }
 
+  /// Return the register which is the program counter.
+  unsigned getProgramCounter() const {
+    return PCReg;
+  }
+
   const MCRegisterDesc &operator[](unsigned RegNo) const {
     assert(RegNo < NumRegs &&
            "Attempting to access record for invalid register number!");

lib/Target/ARM/ARMBaseRegisterInfo.cpp

@@ -45,7 +45,7 @@ using namespace llvm;
 
 ARMBaseRegisterInfo::ARMBaseRegisterInfo(const ARMBaseInstrInfo &tii,
                                          const ARMSubtarget &sti)
-  : ARMGenRegisterInfo(ARM::LR), TII(tii), STI(sti),
+  : ARMGenRegisterInfo(ARM::LR, 0, 0, ARM::PC), TII(tii), STI(sti),
     FramePtr((STI.isTargetDarwin() || STI.isThumb()) ? ARM::R7 : ARM::R11),
     BasePtr(ARM::R6) {
 }

lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp

@@ -146,7 +146,7 @@ static MCInstrInfo *createARMMCInstrInfo() {
 
 static MCRegisterInfo *createARMMCRegisterInfo(StringRef Triple) {
   MCRegisterInfo *X = new MCRegisterInfo();
-  InitARMMCRegisterInfo(X, ARM::LR);
+  InitARMMCRegisterInfo(X, ARM::LR, 0, 0, ARM::PC);
   return X;
 }
 

lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp

@@ -257,7 +257,8 @@ static MCRegisterInfo *createX86MCRegisterInfo(StringRef TT) {
   MCRegisterInfo *X = new MCRegisterInfo();
   InitX86MCRegisterInfo(X, RA,
                         X86_MC::getDwarfRegFlavour(TT, false),
-                        X86_MC::getDwarfRegFlavour(TT, true));
+                        X86_MC::getDwarfRegFlavour(TT, true),
+                        RA);
   X86_MC::InitLLVM2SEHRegisterMapping(X);
   return X;
 }

lib/Target/X86/X86RegisterInfo.cpp

@@ -56,10 +56,12 @@ EnableBasePointer("x86-use-base-pointer", cl::Hidden, cl::init(true),
 
 X86RegisterInfo::X86RegisterInfo(X86TargetMachine &tm,
                                  const TargetInstrInfo &tii)
-  : X86GenRegisterInfo(tm.getSubtarget<X86Subtarget>().is64Bit()
-                         ? X86::RIP : X86::EIP,
+  : X86GenRegisterInfo((tm.getSubtarget<X86Subtarget>().is64Bit()
+                         ? X86::RIP : X86::EIP),
                        X86_MC::getDwarfRegFlavour(tm.getTargetTriple(), false),
-                       X86_MC::getDwarfRegFlavour(tm.getTargetTriple(), true)),
+                       X86_MC::getDwarfRegFlavour(tm.getTargetTriple(), true),
+                       (tm.getSubtarget<X86Subtarget>().is64Bit()
+                         ? X86::RIP : X86::EIP)),
                        TM(tm), TII(tii) {
   X86_MC::InitLLVM2SEHRegisterMapping(this);
 

utils/TableGen/RegisterInfoEmitter.cpp

@@ -921,9 +921,9 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
   // MCRegisterInfo initialization routine.
   OS << "static inline void Init" << TargetName
      << "MCRegisterInfo(MCRegisterInfo *RI, unsigned RA, "
-     << "unsigned DwarfFlavour = 0, unsigned EHFlavour = 0) {\n"
+     << "unsigned DwarfFlavour = 0, unsigned EHFlavour = 0, unsigned PC = 0) {\n"
      << "  RI->InitMCRegisterInfo(" << TargetName << "RegDesc, "
-     << Regs.size()+1 << ", RA, " << TargetName << "MCRegisterClasses, "
+     << Regs.size()+1 << ", RA, PC, " << TargetName << "MCRegisterClasses, "
      << RegisterClasses.size() << ", "
      << TargetName << "RegUnitRoots, "
      << RegBank.getNumNativeRegUnits() << ", "
@@ -958,7 +958,7 @@ RegisterInfoEmitter::runTargetHeader(raw_ostream &OS, CodeGenTarget &Target,
 
   OS << "struct " << ClassName << " : public TargetRegisterInfo {\n"
      << "  explicit " << ClassName
-     << "(unsigned RA, unsigned D = 0, unsigned E = 0);\n"
+     << "(unsigned RA, unsigned D = 0, unsigned E = 0, unsigned PC = 0);\n"
      << "  virtual bool needsStackRealignment(const MachineFunction &) const\n"
      << "     { return false; }\n";
   if (!RegBank.getSubRegIndices().empty()) {
@@ -1267,12 +1267,12 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
   EmitRegMappingTables(OS, Regs, true);
 
   OS << ClassName << "::\n" << ClassName
-     << "(unsigned RA, unsigned DwarfFlavour, unsigned EHFlavour)\n"
+     << "(unsigned RA, unsigned DwarfFlavour, unsigned EHFlavour, unsigned PC)\n"
      << "  : TargetRegisterInfo(" << TargetName << "RegInfoDesc"
      << ", RegisterClasses, RegisterClasses+" << RegisterClasses.size() <<",\n"
      << "             SubRegIndexNameTable, SubRegIndexLaneMaskTable) {\n"
      << "  InitMCRegisterInfo(" << TargetName << "RegDesc, "
-     << Regs.size()+1 << ", RA,\n                     " << TargetName
+     << Regs.size()+1 << ", RA, PC,\n                     " << TargetName
      << "MCRegisterClasses, " << RegisterClasses.size() << ",\n"
      << "                     " << TargetName << "RegUnitRoots,\n"
      << "                     " << RegBank.getNumNativeRegUnits() << ",\n"