[mips] Enforce compact branch register restrictions
Enforce compact branch register restrictions such as the use of the zero
register, both operands being the same register. Emit clear error in such
cases as the issue is subtle.
For bovc and bnvc, silently fixup such cases when emitting objects directly,
like LLVM started doing in rL269899.
Reviewers: vkalintiris, dsanders
Differential Review: http://reviews.llvm.org/D20475
llvm-svn: 271301
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
index 3806b68..fce4efd 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
@@ -117,9 +117,15 @@
unsigned Reg0 = Ctx.getRegisterInfo()->getEncodingValue(RegOp0);
unsigned Reg1 = Ctx.getRegisterInfo()->getEncodingValue(RegOp1);
- assert(Reg0 != Reg1 && "Instruction has bad operands ($rs == $rt)!");
- if (Reg0 < Reg1)
- return;
+ if (Inst.getOpcode() == Mips::BNEC || Inst.getOpcode() == Mips::BEQC) {
+ assert(Reg0 != Reg1 && "Instruction has bad operands ($rs == $rt)!");
+ if (Reg0 < Reg1)
+ return;
+ } else if (Inst.getOpcode() == Mips::BNVC || Inst.getOpcode() == Mips::BOVC) {
+ if (Reg0 >= Reg1)
+ return;
+ } else
+ llvm_unreachable("Cannot rewrite unknown branch!");
Inst.getOperand(0).setReg(RegOp1);
Inst.getOperand(1).setReg(RegOp0);
@@ -181,9 +187,11 @@
case Mips::DINS:
LowerDins(TmpInst);
break;
- // Compact branches.
+ // Compact branches, enforce encoding restrictions.
case Mips::BEQC:
case Mips::BNEC:
+ case Mips::BOVC:
+ case Mips::BNVC:
LowerCompactBranch(TmpInst);
}