[mips][ias] Implement .cpreturn directive.

Summary:
Based on a patch by David Chisnall. I've modified the original patch as follows:
* Moved the expansion to the TargetStreamers so that the directive isn't
  expanded when emitting assembly.
* Fixed an operand order bug.
* Changed the move instructions from DADDu to OR to match recent changes to GAS.

Reviewers: vkalintiris

Subscribers: llvm-commits, emaste, seanbruno, theraven

Differential Revision: http://reviews.llvm.org/D13017

llvm-svn: 248258

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
index 4e865663fc0..994126e83b6 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
@@ -96,6 +96,8 @@ void MipsTargetStreamer::emitDirectiveCpRestore(
 void MipsTargetStreamer::emitDirectiveCpsetup(unsigned RegNo, int RegOrOffset,
                                               const MCSymbol &Sym, bool IsReg) {
 }
+void MipsTargetStreamer::emitDirectiveCpreturn(unsigned SaveLocation,
+                                               bool SaveLocationIsRegister) {}
 
 void MipsTargetStreamer::emitDirectiveModuleFP() {}
 
@@ -387,6 +389,12 @@ void MipsTargetAsmStreamer::emitDirectiveCpsetup(unsigned RegNo,
   forbidModuleDirective();
 }
 
+void MipsTargetAsmStreamer::emitDirectiveCpreturn(unsigned SaveLocation,
+                                                  bool SaveLocationIsRegister) {
+  OS << "\t.cpreturn";
+  forbidModuleDirective();
+}
+
 void MipsTargetAsmStreamer::emitDirectiveModuleFP() {
   OS << "\t.module\tfp=";
   OS << ABIFlagsSection.getFpABIString(ABIFlagsSection.getFpABI()) << "\n";
@@ -838,6 +846,30 @@ void MipsTargetELFStreamer::emitDirectiveCpsetup(unsigned RegNo,
   forbidModuleDirective();
 }
 
+void MipsTargetELFStreamer::emitDirectiveCpreturn(unsigned SaveLocation,
+                                                  bool SaveLocationIsRegister) {
+  // Only N32 and N64 emit anything for .cpreturn iff PIC is set.
+  if (!Pic || !(getABI().IsN32() || getABI().IsN64()))
+    return;
+
+  MCInst Inst;
+  // Either restore the old $gp from a register or on the stack
+  if (SaveLocationIsRegister) {
+    Inst.setOpcode(Mips::OR);
+    Inst.addOperand(MCOperand::createReg(Mips::GP));
+    Inst.addOperand(MCOperand::createReg(SaveLocation));
+    Inst.addOperand(MCOperand::createReg(Mips::ZERO));
+  } else {
+    Inst.setOpcode(Mips::LD);
+    Inst.addOperand(MCOperand::createReg(Mips::GP));
+    Inst.addOperand(MCOperand::createReg(Mips::SP));
+    Inst.addOperand(MCOperand::createImm(SaveLocation));
+  }
+  getStreamer().EmitInstruction(Inst, STI);
+
+  forbidModuleDirective();
+}
+
 void MipsTargetELFStreamer::emitMipsAbiFlags() {
   MCAssembler &MCA = getStreamer().getAssembler();
   MCContext &Context = MCA.getContext();