Emit & read more compressed bytecode by not emitting a bytecodeblock for
each basic block in function. Instead, just emit a stream of instructions,
chopping up basic blocks based on when we find terminator instructions. This
saves a fairly substantial chunk of bytecode space. In stripped, sample
cases, for example, we get this reduction in size:
197.parser: 163036 -> 137180: 18.8% reduction
254.gap : 844936 -> 689392: 22.6%
255.vortex: 621724 -> 528444: 17.7%
...
Not bad for something this simple. :) Note that this doesn't require a new
bytecode version number at all, though version 1.1 should not need to support
the old format.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10280 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bytecode/Reader/Reader.cpp b/lib/Bytecode/Reader/Reader.cpp
index ed8f9e8..097d548 100644
--- a/lib/Bytecode/Reader/Reader.cpp
+++ b/lib/Bytecode/Reader/Reader.cpp
@@ -188,7 +188,8 @@
}
}
-
+/// ParseBasicBlock - In LLVM 1.0 bytecode files, we used to output one
+/// basicblock at a time. This method reads in one of the basicblock packets.
BasicBlock *BytecodeParser::ParseBasicBlock(const unsigned char *&Buf,
const unsigned char *EndBuf,
unsigned BlockNo) {
@@ -207,6 +208,38 @@
return BB;
}
+
+/// ParseInstructionList - Parse all of the BasicBlock's & Instruction's in the
+/// body of a function. In post 1.0 bytecode files, we no longer emit basic
+/// block individually, in order to avoid per-basic-block overhead.
+unsigned BytecodeParser::ParseInstructionList(Function *F,
+ const unsigned char *&Buf,
+ const unsigned char *EndBuf) {
+ unsigned BlockNo = 0;
+ std::vector<unsigned> Args;
+
+ while (Buf < EndBuf) {
+ BasicBlock *BB;
+ if (ParsedBasicBlocks.size() == BlockNo)
+ ParsedBasicBlocks.push_back(BB = new BasicBlock());
+ else if (ParsedBasicBlocks[BlockNo] == 0)
+ BB = ParsedBasicBlocks[BlockNo] = new BasicBlock();
+ else
+ BB = ParsedBasicBlocks[BlockNo];
+ ++BlockNo;
+ F->getBasicBlockList().push_back(BB);
+
+ // Read instructions into this basic block until we get to a terminator
+ while (Buf < EndBuf && !BB->getTerminator())
+ ParseInstruction(Buf, EndBuf, Args, BB);
+
+ if (!BB->getTerminator())
+ throw std::string("Non-terminated basic block found!");
+ }
+
+ return BlockNo;
+}
+
void BytecodeParser::ParseSymbolTable(const unsigned char *&Buf,
const unsigned char *EndBuf,
SymbolTable *ST,
@@ -345,6 +378,13 @@
break;
}
+ case BytecodeFormat::InstructionList: {
+ BCR_TRACE(2, "BLOCK BytecodeFormat::InstructionList: {\n");
+ if (BlockNum) throw std::string("Already parsed basic blocks!");
+ BlockNum = ParseInstructionList(F, Buf, Buf+Size);
+ break;
+ }
+
case BytecodeFormat::SymbolTable:
BCR_TRACE(2, "BLOCK BytecodeFormat::SymbolTable: {\n");
ParseSymbolTable(Buf, Buf+Size, &F->getSymbolTable(), F);