Encoding of destination fixup for ARM branch and conditional branch

instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118801 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMAsmBackend.cpp

@@ -138,12 +138,13 @@ public:
   }
 };
 
-static unsigned getFixupKindLog2Size(unsigned Kind) {
+static unsigned getFixupKindNumBytes(unsigned Kind) {
   switch (Kind) {
   default: llvm_unreachable("Unknown fixup kind!");
-  case FK_Data_4: return 2;
+  case FK_Data_4: return 4;
   case ARM::fixup_arm_pcrel_12: return 2;
   case ARM::fixup_arm_vfp_pcrel_12: return 1;
+  case ARM::fixup_arm_branch: return 3;
   }
 }
 
@@ -156,16 +157,17 @@ static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
   case ARM::fixup_arm_pcrel_12:
     // ARM PC-relative values are offset by 8.
     return Value - 8;
+  case ARM::fixup_arm_branch:
   case ARM::fixup_arm_vfp_pcrel_12:
-    // The VFP ld/st immediate value doesn't encode the low two bits since
+    // These values don't encode the low two bits since they're always zero.
-    // they're always zero. Offset by 8 just as above.
+    // Offset by 8 just as above.
     return (Value - 8) >> 2;
   }
 }
 
 void DarwinARMAsmBackend::ApplyFixup(const MCFixup &Fixup, MCDataFragment &DF,
-                                  uint64_t Value) const {
+                                     uint64_t Value) const {
-  unsigned NumBytes = getFixupKindLog2Size(Fixup.getKind());
+  unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
   Value = adjustFixupValue(Fixup.getKind(), Value);
 
   assert(Fixup.getOffset() + NumBytes <= DF.getContents().size() &&

lib/Target/ARM/ARMCodeEmitter.cpp

@@ -161,6 +161,8 @@ namespace {
     //  are already handled elsewhere. They are placeholders to allow this
     //  encoder to continue to function until the MC encoder is sufficiently
     //  far along that this one can be eliminated entirely.
+    unsigned getBranchTargetOpValue(const MachineInstr &MI, unsigned Op)
+      const { return 0; }
     unsigned getCCOutOpValue(const MachineInstr &MI, unsigned Op)
       const { return 0; }
     unsigned getSOImmOpValue(const MachineInstr &MI, unsigned Op)

lib/Target/ARM/ARMFixupKinds.h

@@ -20,7 +20,14 @@ enum Fixups {
   // fixup_arm_vfp_pcrel_12 - 12-bit PC relative relocation for symbol addresses
   // used in VFP instructions where the lower 2 bits are not encoded (so it's
   // encoded as an 8-bit immediate).
-  fixup_arm_vfp_pcrel_12
+  fixup_arm_vfp_pcrel_12,
+  // fixup_arm_brnach - 24-bit PC relative relocation for direct branch
+  // instructions.
+  fixup_arm_branch,
+
+  // Marker
+  LastTargetFixupKind,
+  NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind
 };
 }
 }

lib/Target/ARM/ARMInstrInfo.td

@@ -274,7 +274,9 @@ def sube_live_carry :
 //
 
 // Branch target.
-def brtarget : Operand<OtherVT>;
+def brtarget : Operand<OtherVT> {
+  string EncoderMethod = "getBranchTargetOpValue";
+}
 
 // A list of registers separated by comma. Used by load/store multiple.
 def reglist : Operand<i32> {
@@ -1363,7 +1365,10 @@ let isBranch = 1, isTerminator = 1 in {
   let isBarrier = 1 in {
     let isPredicable = 1 in
     def B : ABXI<0b1010, (outs), (ins brtarget:$target), IIC_Br,
-                "b\t$target", [(br bb:$target)]>;
+                "b\t$target", [(br bb:$target)]> {
+      bits<24> target;
+      let Inst{23-0} = target;
+    }
 
     let isNotDuplicable = 1, isIndirectBranch = 1,
         // FIXME: $imm field is not specified by asm string.  Mark as cgonly.
@@ -1406,7 +1411,10 @@ let isBranch = 1, isTerminator = 1 in {
   // a two-value operand where a dag node expects two operands. :(
   def Bcc : ABI<0b1010, (outs), (ins brtarget:$target),
                IIC_Br, "b", "\t$target",
-               [/*(ARMbrcond bb:$target, imm:$cc, CCR:$ccr)*/]>;
+               [/*(ARMbrcond bb:$target, imm:$cc, CCR:$ccr)*/]> {
+    bits<24> target;
+    let Inst{23-0} = target;
+  }
 }
 
 // Branch and Exchange Jazelle -- for disassembly only

lib/Target/ARM/ARMMCCodeEmitter.cpp

@@ -41,12 +41,14 @@ public:
 
   ~ARMMCCodeEmitter() {}
 
-  unsigned getNumFixupKinds() const { return 2; }
+  unsigned getNumFixupKinds() const { return ARM::NumTargetFixupKinds; }
 
   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
     const static MCFixupKindInfo Infos[] = {
-      { "fixup_arm_pcrel_12", 2, 12, MCFixupKindInfo::FKF_IsPCRel },
+      // name                     offset  bits  flags
-      { "fixup_arm_vfp_pcrel_12", 3, 8, MCFixupKindInfo::FKF_IsPCRel },
+      { "fixup_arm_pcrel_12",     2,      12,   MCFixupKindInfo::FKF_IsPCRel },
+      { "fixup_arm_vfp_pcrel_12", 3,      8,    MCFixupKindInfo::FKF_IsPCRel },
+      { "fixup_arm_branch",       1,      24,   MCFixupKindInfo::FKF_IsPCRel },
     };
 
     if (Kind < FirstTargetFixupKind)
@@ -72,6 +74,11 @@ public:
                               unsigned &Reg, unsigned &Imm,
                               SmallVectorImpl<MCFixup> &Fixups) const;
 
+  /// getBranchTargetOpValue - Return encoding info for 24-bit immediate
+  /// branch target.
+  uint32_t getBranchTargetOpValue(const MCInst &MI, unsigned OpIdx,
+                                  SmallVectorImpl<MCFixup> &Fixups) const;
+
   /// getAddrModeImm12OpValue - Return encoding info for 'reg +/- imm12'
   /// operand.
   uint32_t getAddrModeImm12OpValue(const MCInst &MI, unsigned OpIdx,
@@ -247,6 +254,24 @@ EncodeAddrModeOpValues(const MCInst &MI, unsigned OpIdx, unsigned &Reg,
   return isAdd;
 }
 
+/// getBranchTargetOpValue - Return encoding info for 24-bit immediate
+/// branch target.
+uint32_t ARMMCCodeEmitter::
+getBranchTargetOpValue(const MCInst &MI, unsigned OpIdx,
+                        SmallVectorImpl<MCFixup> &Fixups) const {
+  const MCOperand &MO = MI.getOperand(OpIdx);
+
+  // If the destination is an immediate, we have nothing to do.
+  if (MO.isImm()) return MO.getImm();
+  assert (MO.isExpr() && "Unexpected branch target type!");
+  const MCExpr *Expr = MO.getExpr();
+  MCFixupKind Kind = MCFixupKind(ARM::fixup_arm_branch);
+  Fixups.push_back(MCFixup::Create(0, Expr, Kind));
+
+  // All of the information is in the fixup.
+  return 0;
+}
+
 /// getAddrModeImm12OpValue - Return encoding info for 'reg +/- imm12' operand.
 uint32_t ARMMCCodeEmitter::
 getAddrModeImm12OpValue(const MCInst &MI, unsigned OpIdx,