PNaCl wire format: Use FORWARDTYPEREF consistently for all forward references

Before this change, the writer would only emit FORWARDTYPEREF for some
operands, e.g. the first operand of BINOP but not the second, on the
grounds that the type of the second operand can be inferred.  However,
that makes the format complicated.

Change the writer so that it always emits FORWARDTYPEREF for a forward
ref.  This unifies PushValueAndType() and pushValue().  pushValue()
gains a call to EmitFnForwardTypeRef() so becomes the same as
PushValueAndType().

Change the reader to be stricter, so that it requires a FORWARDTYPEREF
to have been emitted in most cases.  This is done by ignoring the
implied type argument.

Tasks still remaining:

 * Make reader stricter so that multiple FORWARDTYPEREFs are disallowed.
 * Remove now-unused Type arguments in the reader.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3507
TEST=new llvm-lit test + PNaCl toolchain trybots

Review URL: https://codereview.chromium.org/17806003

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.h b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.h
index 57757e7ded..e6ea6266be 100644
--- a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.h
+++ b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.h
@@ -297,6 +297,7 @@ private:
 
   /// getValue -- Version of getValue that returns ResVal directly,
   /// or 0 if there is an error.
+  /// TODO(mseaborn): Remove the unused Type argument from this function.
   Value *getValue(SmallVector<uint64_t, 64> &Record, unsigned Slot,
                   unsigned InstNum, Type *Ty) {
     if (Slot == Record.size()) return 0;
@@ -304,10 +305,11 @@ private:
     // Adjust the ValNo, if it was encoded relative to the InstNum.
     if (UseRelativeIDs)
       ValNo = InstNum - ValNo;
-    return getOrCreateFnValueByID(ValNo, Ty);
+    return getFnValueByID(ValNo);
   }
 
   /// getValueSigned -- Like getValue, but decodes signed VBRs.
+  /// TODO(mseaborn): Remove the unused Type argument from this function.
   Value *getValueSigned(SmallVector<uint64_t, 64> &Record, unsigned Slot,
                         unsigned InstNum, Type *Ty) {
     if (Slot == Record.size()) return 0;
@@ -315,7 +317,7 @@ private:
     // Adjust the ValNo, if it was encoded relative to the InstNum.
     if (UseRelativeIDs)
       ValNo = InstNum - ValNo;
-    return getOrCreateFnValueByID(ValNo, Ty);
+    return getFnValueByID(ValNo);
   }
 
   bool ParseModule(bool Resume);