[opaque pointer type] bitcode support for explicit type parameter to the load instruction

Summary:
I've taken my best guess at this, but I've cargo culted in places & so
explanations/corrections would be great.

This seems to pass all the tests (check-all, covering clang and llvm) so I
believe that pretty well exercises both the backwards compatibility and common
(same version) compatibility given the number of checked in bitcode files we
already have. Is that a reasonable approach to testing here? Would some more
explicit tests be desired?

1) is this the right way to do back-compat in this case (looking at the number
  of entries in the bitcode record to disambiguate between the old schema and
  the new?)

2) I don't quite understand the logarithm logic to choose the encoding type of
  the type parameter in the abbreviation description, but I found another
  instruction doing the same thing & it seems to work. Is that the right
  approach?

Reviewers: dexonsmith

Differential Revision: http://reviews.llvm.org/D7655

llvm-svn: 230414

1 files changed, 19 insertions, 2 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 3b3a6eb..c45e964 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3574,12 +3574,21 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
       unsigned OpNum = 0;
       Value *Op;
       if (getValueTypePair(Record, OpNum, NextValueNo, Op) ||
-          OpNum+2 != Record.size())
+          (OpNum + 2 != Record.size() && OpNum + 3 != Record.size()))
         return Error("Invalid record");
+
+      Type *Ty = nullptr;
+      if (OpNum + 3 == Record.size())
+        Ty = getTypeByID(Record[OpNum++]);
+
       unsigned Align;
       if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
         return EC;
       I = new LoadInst(Op, "", Record[OpNum+1], Align);
+
+      assert((!Ty || Ty == I->getType()) &&
+             "Explicit type doesn't match pointee type of the first operand");
+
       InstructionList.push_back(I);
       break;
     }
@@ -3588,9 +3597,13 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
       unsigned OpNum = 0;
       Value *Op;
       if (getValueTypePair(Record, OpNum, NextValueNo, Op) ||
-          OpNum+4 != Record.size())
+          (OpNum + 4 != Record.size() && OpNum + 5 != Record.size()))
         return Error("Invalid record");
 
+      Type *Ty = nullptr;
+      if (OpNum + 5 == Record.size())
+        Ty = getTypeByID(Record[OpNum++]);
+
       AtomicOrdering Ordering = GetDecodedOrdering(Record[OpNum+2]);
       if (Ordering == NotAtomic || Ordering == Release ||
           Ordering == AcquireRelease)
@@ -3603,6 +3616,10 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
       if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
         return EC;
       I = new LoadInst(Op, "", Record[OpNum+1], Align, Ordering, SynchScope);
+
+      assert((!Ty || Ty == I->getType()) &&
+             "Explicit type doesn't match pointee type of the first operand");
+
       InstructionList.push_back(I);
       break;
     }