From: Peter Collingbourne <peter@pcc.me.uk>
Date: Thu, 1 Dec 2016 05:47:58 +0000 (+0000)
Subject: Bitcode: Correctly handle Fixed and VBR arrays in BitstreamCursor::skipRecord().
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ca0a598f5b492a67f7f29434dbf175215cde8777;p=llvm

Bitcode: Correctly handle Fixed and VBR arrays in BitstreamCursor::skipRecord().

The assertions were wrong; we need to call getEncodingData() on the element,
not the array. While here, simplify the skipRecord() implementation for Fixed
and Char6 arrays. This is tested by the code I added to llvm-bcanalyzer
which makes sure that we can skip any record.

Differential Revision: https://reviews.llvm.org/D27241

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288315 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Bitcode/Reader/BitstreamReader.cpp b/lib/Bitcode/Reader/BitstreamReader.cpp
index f1237069f7b..43c9aebd79e 100644
--- a/lib/Bitcode/Reader/BitstreamReader.cpp
+++ b/lib/Bitcode/Reader/BitstreamReader.cpp
@@ -131,18 +131,16 @@ void BitstreamCursor::skipRecord(unsigned AbbrevID) {
       default:
         report_fatal_error("Array element type can't be an Array or a Blob");
       case BitCodeAbbrevOp::Fixed:
-        assert((unsigned)Op.getEncodingData() <= MaxChunkSize);
-        for (; NumElts; --NumElts)
-          Read((unsigned)EltEnc.getEncodingData());
+        assert((unsigned)EltEnc.getEncodingData() <= MaxChunkSize);
+        JumpToBit(GetCurrentBitNo() + NumElts * EltEnc.getEncodingData());
         break;
       case BitCodeAbbrevOp::VBR:
-        assert((unsigned)Op.getEncodingData() <= MaxChunkSize);
+        assert((unsigned)EltEnc.getEncodingData() <= MaxChunkSize);
         for (; NumElts; --NumElts)
           ReadVBR64((unsigned)EltEnc.getEncodingData());
         break;
       case BitCodeAbbrevOp::Char6:
-        for (; NumElts; --NumElts)
-          Read(6);
+        JumpToBit(GetCurrentBitNo() + NumElts * 6);
         break;
       }
       continue;
diff --git a/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp b/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
index 14957e60b2b..d866201723a 100644
--- a/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
+++ b/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
@@ -567,7 +567,7 @@ static bool ParseBlock(BitstreamCursor &Stream, BitstreamBlockInfo &BlockInfo,
     ++BlockStats.NumRecords;
 
     StringRef Blob;
-    unsigned CurrentRecordPos = Stream.getCurrentByteNo();
+    unsigned CurrentRecordPos = Stream.GetCurrentBitNo();
     unsigned Code = Stream.readRecord(Entry.ID, Record, &Blob);
 
     // Increment the # occurrences of this code.
@@ -608,7 +608,7 @@ static bool ParseBlock(BitstreamCursor &Stream, BitstreamBlockInfo &BlockInfo,
           SHA1 Hasher;
           StringRef Hash;
           {
-            int BlockSize = CurrentRecordPos - BlockEntryPos;
+            int BlockSize = (CurrentRecordPos / 8) - BlockEntryPos;
             auto Ptr = Stream.getPointerToByte(BlockEntryPos, BlockSize);
             Hasher.update(ArrayRef<uint8_t>(Ptr, BlockSize));
             Hash = Hasher.result();
@@ -675,6 +675,10 @@ static bool ParseBlock(BitstreamCursor &Stream, BitstreamBlockInfo &BlockInfo,
 
       outs() << "\n";
     }
+
+    // Make sure that we can skip the current record.
+    Stream.JumpToBit(CurrentRecordPos);
+    Stream.skipRecord(Entry.ID);
   }
 }