PNaCl wire format: Clean up representation of "alloca" instruction

For some reason, the size operand of "alloca" was represented using an
absolute value ID + type, unlike other instructions where relative
value IDs are used.

Change the "alloca" representation to be consistent with other
instructions, so that we can use PushValueAndType() in the writer and
getValue() in the reader.

Also take this opportunity to remove the field for alloca's result
type, since it's always i8* in PNaCl.

This is part of a cleanup to make forward reference handling stricter:
it removes a use of getOrCreateFnValueByID(), which isn't strict (that
is, it doesn't reject duplicate FORWARDTYPEREF records).

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3507
TEST=PNaCl toolchain trybots

Review URL: https://codereview.chromium.org/17757004

1 files changed, 8 insertions, 9 deletions

diff --git a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
index 57dcea8953..8defdb5d1b 100644
--- a/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
+++ b/lib/Bitcode/NaCl/Reader/NaClBitcodeReader.cpp
@@ -2283,16 +2283,15 @@ bool NaClBitcodeReader::ParseFunctionBody(Function *F) {
       break;
     }
 
-    case naclbitc::FUNC_CODE_INST_ALLOCA: { // ALLOCA: [instty, opty, op, align]
-      if (Record.size() != 4)
+    case naclbitc::FUNC_CODE_INST_ALLOCA: { // ALLOCA: [op, align]
+      if (Record.size() != 2)
+        return Error("Invalid ALLOCA record");
+      Value *Size;
+      unsigned OpNum = 0;
+      if (getValue(Record, OpNum, NextValueNo, Size))
         return Error("Invalid ALLOCA record");
-      PointerType *Ty =
-        dyn_cast_or_null<PointerType>(getTypeByID(Record[0]));
-      Type *OpTy = getTypeByID(Record[1]);
-      Value *Size = getOrCreateFnValueByID(Record[2], OpTy);
-      unsigned Align = Record[3];
-      if (!Ty || !Size) return Error("Invalid ALLOCA record");
-      I = new AllocaInst(Ty->getElementType(), Size, (1 << Align) >> 1);
+      unsigned Align = Record[1];
+      I = new AllocaInst(Type::getInt8Ty(Context), Size, (1 << Align) >> 1);
       InstructionList.push_back(I);
       break;
     }