Bytecode File Format Changes:
- File format version number bumped to 4
- Writer will now align nothing
- Reader now only expects alignment for version 3 or earlier
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15875 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bytecode/Reader/Reader.cpp b/lib/Bytecode/Reader/Reader.cpp
index 9ca6419..85a890d 100644
--- a/lib/Bytecode/Reader/Reader.cpp
+++ b/lib/Bytecode/Reader/Reader.cpp
@@ -72,12 +72,14 @@
/// Align the buffer position to a 32 bit boundary
inline void BytecodeReader::align32() {
- BufPtr Save = At;
- At = (const unsigned char *)((unsigned long)(At+3) & (~3UL));
- if (At > Save)
- if (Handler) Handler->handleAlignment(At - Save);
- if (At > BlockEnd)
- error("Ran out of data while aligning!");
+ if (hasAlignment) {
+ BufPtr Save = At;
+ At = (const unsigned char *)((unsigned long)(At+3) & (~3UL));
+ if (At > Save)
+ if (Handler) Handler->handleAlignment(At - Save);
+ if (At > BlockEnd)
+ error("Ran out of data while aligning!");
+ }
}
/// Read a whole unsigned integer
@@ -1886,6 +1888,7 @@
hasLongBlockHeaders = false;
has32BitTypes = false;
hasNoDependentLibraries = false;
+ hasAlignment = false;
switch (RevisionNum) {
case 0: // LLVM 1.0, 1.1 release version
@@ -1937,6 +1940,14 @@
// FALL THROUGH
case 3: // LLVM 1.3 release version
+ /// LLVM 1.3 and earlier caused alignment bytes to be written on some block
+ /// boundaries and at the end of some strings. In extreme cases (e.g. lots
+ /// of GEP references to a constant array), this can increase the file size
+ /// by 30% or more. In version 1.4 alignment is done away with completely.
+ hasAlignment = true;
+
+ // FALL THROUGH
+ case 4:
break;
default: