[GlobalISel] Add a G_JUMP_TABLE opcode.

This opcode generates a pointer to the address of the jump table
specified by the source operand, which is a jump table index.

It will be used in conjunction with an upcoming G_BRJT opcode to support
jump table codegen with GlobalISel.

Differential Revision: https://reviews.llvm.org/D63111

llvm-svn: 363096

2 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index d58a4629815..f6eac395616 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -179,6 +179,12 @@ MachineInstrBuilder MachineIRBuilder::buildGlobalValue(unsigned Res,
       .addGlobalAddress(GV);
 }
 
+MachineInstrBuilder MachineIRBuilder::buildJumpTable(const LLT PtrTy,
+                                                     unsigned JTI) {
+  return buildInstr(TargetOpcode::G_JUMP_TABLE, {PtrTy}, {})
+      .addJumpTableIndex(JTI);
+}
+
 void MachineIRBuilder::validateBinaryOp(const LLT &Res, const LLT &Op0,
                                         const LLT &Op1) {
   assert((Res.isScalar() || Res.isVector()) && "invalid operand type");
diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index b1964d68111..78072a482dd 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -1312,6 +1312,14 @@ void MachineVerifier::verifyPreISelGenericInstruction(const MachineInstr *MI) {
 
     break;
   }
+  case TargetOpcode::G_JUMP_TABLE: {
+    if (!MI->getOperand(1).isJTI())
+      report("G_JUMP_TABLE source operand must be a jump table index", MI);
+    LLT DstTy = MRI->getType(MI->getOperand(0).getReg());
+    if (!DstTy.isPointer())
+      report("G_JUMP_TABLE dest operand must have a pointer type", MI);
+    break;
+  }
   default:
     break;
   }