[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.

llvm-svn: 184721

1 files changed, 28 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp
index 420c01ba9e7..1c6adac33e3 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCCodeEmitter.cpp
+++ b/llvm/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);