[IR] Add Freeze instruction

Summary:
- Define Instruction::Freeze, let it be UnaryOperator
- Add support for freeze to LLLexer/LLParser/BitcodeReader/BitcodeWriter
  The format is `%x = freeze <ty> %v`
- Add support for freeze instruction to llvm-c interface.
- Add m_Freeze in PatternMatch.
- Erase freeze when lowering IR to SelDag.

Reviewers: deadalnix, hfinkel, efriedma, lebedev.ri, nlopes, jdoerfert, regehr, filcab, delcypher, whitequark

Reviewed By: lebedev.ri, jdoerfert

Subscribers: jfb, kristof.beyls, hiraditya, lebedev.ri, steven_wu, dexonsmith, xbolva00, delcypher, spatel, regehr, trentxintong, vsk, filcab, nlopes, mehdi_amini, deadalnix, llvm-commits

Differential Revision: https://reviews.llvm.org/D29011

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index e89d8b0a9b5..91026c3b1b2 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -3145,6 +3145,9 @@ void Verifier::visitUnaryOperator(UnaryOperator &U) {
     Assert(U.getType()->isFPOrFPVectorTy(),
            "FNeg operator only works with float types!", &U);
     break;
+  case Instruction::Freeze:
+    // Freeze can take all kinds of types.
+    break;
   default:
     llvm_unreachable("Unknown UnaryOperator opcode!");
   }