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

[David Blaikie]

Hi rafael, resistor, grosbach, chandlerc,

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?

http://reviews.llvm.org/D7655

Files:
  lib/Bitcode/Reader/BitcodeReader.cpp
  lib/Bitcode/Writer/BitcodeWriter.cpp

Index: lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- lib/Bitcode/Reader/BitcodeReader.cpp
+++ lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3510,21 +3510,32 @@
       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++]);
+
       I = new LoadInst(Op, "", Record[OpNum+1], (1 << Record[OpNum]) >> 1);
+
+      assert(!Ty || Ty == I->getType());
+
       InstructionList.push_back(I);
       break;
     }
     case bitc::FUNC_CODE_INST_LOADATOMIC: {
        // LOADATOMIC: [opty, op, align, vol, ordering, synchscope]
       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)
@@ -3535,6 +3546,9 @@
 
       I = new LoadInst(Op, "", Record[OpNum+1], (1 << Record[OpNum]) >> 1,
                        Ordering, SynchScope);
+
+      assert(!Ty || Ty == I->getType());
+
       InstructionList.push_back(I);
       break;
     }
Index: lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- lib/Bitcode/Writer/BitcodeWriter.cpp
+++ lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1878,6 +1878,7 @@
       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))  // ptr
         AbbrevToUse = FUNCTION_INST_LOAD_ABBREV;
     }
+    Vals.push_back(VE.getTypeID(I.getType()));
     Vals.push_back(Log2_32(cast<LoadInst>(I).getAlignment())+1);
     Vals.push_back(cast<LoadInst>(I).isVolatile());
     if (cast<LoadInst>(I).isAtomic()) {
@@ -2232,6 +2233,8 @@
     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_LOAD));
     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Ptr
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // dest ty
+                              Log2_32_Ceil(VE.getTypes().size()+1)));
     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // Align
     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // volatile
     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,

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