Check whether MCInst operand isImm before calling getImm.

When processing possible aliases, TableGen assumes that if an operand *can* be
an immediate, then it always *will* be. This is incorrect for the AArch64
backend. This patch inserts a check in the generated code to make sure isImm is
true first.

llvm-svn: 171972

1 files changed, 10 insertions, 4 deletions

diff --git a/llvm/utils/TableGen/AsmWriterEmitter.cpp b/llvm/utils/TableGen/AsmWriterEmitter.cpp
index a4114d9815b..73b083bd94c 100644
--- a/llvm/utils/TableGen/AsmWriterEmitter.cpp
+++ b/llvm/utils/TableGen/AsmWriterEmitter.cpp
@@ -863,12 +863,18 @@ void AsmWriterEmitter::EmitPrintAliasInstruction(raw_ostream &O) {
 
           break;
         }
-        case CodeGenInstAlias::ResultOperand::K_Imm:
-          Cond = std::string("MI->getOperand(") +
-            llvm::utostr(i) + ").getImm() == " +
-            llvm::utostr(CGA->ResultOperands[i].getImm());
+        case CodeGenInstAlias::ResultOperand::K_Imm: {
+          std::string Op = "MI->getOperand(" + llvm::utostr(i) + ")";
+
+          // Just because the alias has an immediate result, doesn't mean the
+          // MCInst will. An MCExpr could be present, for example.
+          IAP->addCond(Op + ".isImm()");
+
+          Cond = Op + ".getImm() == "
+            + llvm::utostr(CGA->ResultOperands[i].getImm());
           IAP->addCond(Cond);
           break;
+        }
         case CodeGenInstAlias::ResultOperand::K_Reg:
           // If this is zero_reg, something's playing tricks we're not
           // equipped to handle.