[PowerPC] Support absolute branches

There is currently only limited support for the "absolute" variants
of branch instructions.  This patch adds support for the absolute
variants of all branches that are currently otherwise supported.

This requires adding new fixup types so that the correct variant
of relocation type can be selected by the object writer.

While the compiler will continue to usually choose the relative
branch variants, this will allow the asm parser to fully support
the absolute branches, with either immediate (numerical) or
symbolic target addresses.

No change in code generation intended.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184721 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 46 insertions, 2 deletions

diff --git a/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index 3fa2e09..e01f142 100644
--- a/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -34,8 +34,10 @@ static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) {
   case PPC::fixup_ppc_nofixup:
     return Value;
   case PPC::fixup_ppc_brcond14:
+  case PPC::fixup_ppc_brcond14abs:
     return Value & 0xfffc;
   case PPC::fixup_ppc_br24:
+  case PPC::fixup_ppc_br24abs:
     return Value & 0x3fffffc;
   case PPC::fixup_ppc_half16:
     return Value & 0xffff;
@@ -56,7 +58,9 @@ static unsigned getFixupKindNumBytes(unsigned Kind) {
     return 2;
   case FK_Data_4:
   case PPC::fixup_ppc_brcond14:
+  case PPC::fixup_ppc_brcond14abs:
   case PPC::fixup_ppc_br24:
+  case PPC::fixup_ppc_br24abs:
     return 4;
   case FK_Data_8:
     return 8;
@@ -93,6 +97,8 @@ public:
       // name                    offset  bits  flags
       { "fixup_ppc_br24",        6,      24,   MCFixupKindInfo::FKF_IsPCRel },
       { "fixup_ppc_brcond14",    16,     14,   MCFixupKindInfo::FKF_IsPCRel },
+      { "fixup_ppc_br24abs",     6,      24,   0 },
+      { "fixup_ppc_brcond14abs", 16,     14,   0 },
       { "fixup_ppc_half16",       0,     16,   0 },
       { "fixup_ppc_half16ds",     0,     14,   0 },
       { "fixup_ppc_tlsreg",       0,      0,   0 },
diff --git a/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp b/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
index 69e84a1..f48cb5e 100644
--- a/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
+++ b/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
@@ -58,9 +58,11 @@ unsigned PPCELFObjectWriter::getRelocTypeInner(const MCValue &Target,
     default:
       llvm_unreachable("Unimplemented");
     case PPC::fixup_ppc_br24:
+    case PPC::fixup_ppc_br24abs:
       Type = ELF::R_PPC_REL24;
       break;
     case PPC::fixup_ppc_brcond14:
+    case PPC::fixup_ppc_brcond14abs:
       Type = ELF::R_PPC_REL14;
       break;
     case PPC::fixup_ppc_half16:
@@ -92,10 +94,10 @@ unsigned PPCELFObjectWriter::getRelocTypeInner(const MCValue &Target,
   } else {
     switch ((unsigned)Fixup.getKind()) {
       default: llvm_unreachable("invalid fixup kind!");
-    case PPC::fixup_ppc_br24:
+    case PPC::fixup_ppc_br24abs:
       Type = ELF::R_PPC_ADDR24;
       break;
-    case PPC::fixup_ppc_brcond14:
+    case PPC::fixup_ppc_brcond14abs:
       Type = ELF::R_PPC_ADDR14; // XXX: or BRNTAKEN?_
       break;
     case PPC::fixup_ppc_half16:
diff --git a/lib/Target/PowerPC/MCTargetDesc/PPCFixupKinds.h b/lib/Target/PowerPC/MCTargetDesc/PPCFixupKinds.h
index 3ea59f0..0438c0e 100644
--- a/lib/Target/PowerPC/MCTargetDesc/PPCFixupKinds.h
+++ b/lib/Target/PowerPC/MCTargetDesc/PPCFixupKinds.h
@@ -25,6 +25,14 @@ enum Fixups {
   /// branches.
   fixup_ppc_brcond14,
   
+  /// fixup_ppc_br24abs - 24-bit absolute relocation for direct branches
+  /// like 'ba' and 'bla'.
+  fixup_ppc_br24abs,
+
+  /// fixup_ppc_brcond14abs - 14-bit absolute relocation for conditional
+  /// branches.
+  fixup_ppc_brcond14abs,
+
   /// fixup_ppc_half16 - A 16-bit fixup corresponding to lo16(_foo)
   /// or ha16(_foo) for instrs like 'li' or 'addis'.
   fixup_ppc_half16,
diff --git a/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp b/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp
index 420c01b..1c6adac 100644
--- a/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp
+++ b/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp
@@ -48,6 +48,10 @@ public:
                                SmallVectorImpl<MCFixup> &Fixups) const;
   unsigned getCondBrEncoding(const MCInst &MI, unsigned OpNo,
                              SmallVectorImpl<MCFixup> &Fixups) const;
+  unsigned getAbsDirectBrEncoding(const MCInst &MI, unsigned OpNo,
+                                  SmallVectorImpl<MCFixup> &Fixups) const;
+  unsigned getAbsCondBrEncoding(const MCInst &MI, unsigned OpNo,
+                                SmallVectorImpl<MCFixup> &Fixups) const;
   unsigned getS16ImmEncoding(const MCInst &MI, unsigned OpNo,
                              SmallVectorImpl<MCFixup> &Fixups) const;
   unsigned getMemRIEncoding(const MCInst &MI, unsigned OpNo,
@@ -134,6 +138,30 @@ unsigned PPCMCCodeEmitter::getCondBrEncoding(const MCInst &MI, unsigned OpNo,
   return 0;
 }
 
+unsigned PPCMCCodeEmitter::
+getAbsDirectBrEncoding(const MCInst &MI, unsigned OpNo,
+                       SmallVectorImpl<MCFixup> &Fixups) const {
+  const MCOperand &MO = MI.getOperand(OpNo);
+  if (MO.isReg() || MO.isImm()) return getMachineOpValue(MI, MO, Fixups);
+
+  // Add a fixup for the branch target.
+  Fixups.push_back(MCFixup::Create(0, MO.getExpr(),
+                                   (MCFixupKind)PPC::fixup_ppc_br24abs));
+  return 0;
+}
+
+unsigned PPCMCCodeEmitter::
+getAbsCondBrEncoding(const MCInst &MI, unsigned OpNo,
+                     SmallVectorImpl<MCFixup> &Fixups) const {
+  const MCOperand &MO = MI.getOperand(OpNo);
+  if (MO.isReg() || MO.isImm()) return getMachineOpValue(MI, MO, Fixups);
+
+  // Add a fixup for the branch target.
+  Fixups.push_back(MCFixup::Create(0, MO.getExpr(),
+                                   (MCFixupKind)PPC::fixup_ppc_brcond14abs));
+  return 0;
+}
+
 unsigned PPCMCCodeEmitter::getS16ImmEncoding(const MCInst &MI, unsigned OpNo,
                                        SmallVectorImpl<MCFixup> &Fixups) const {
   const MCOperand &MO = MI.getOperand(OpNo);