Save another 30K from 176.gcc by encoding the compaction table a bit more
intelligently.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10918 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Bytecode/Reader/Reader.cpp b/lib/Bytecode/Reader/Reader.cpp
index 2067f22..f4b620e 100644
--- a/lib/Bytecode/Reader/Reader.cpp
+++ b/lib/Bytecode/Reader/Reader.cpp
@@ -496,8 +496,22 @@
const unsigned char *End) {
while (Buf != End) {
- unsigned NumEntries = read_vbr_uint(Buf, End);
- unsigned Ty = read_vbr_uint(Buf, End);
+ unsigned NumEntries;
+ unsigned Ty;
+
+ NumEntries = read_vbr_uint(Buf, End);
+ switch (NumEntries & 3) {
+ case 0:
+ case 1:
+ case 2:
+ Ty = NumEntries >> 2;
+ NumEntries &= 3;
+ break;
+ case 3:
+ NumEntries >>= 2;
+ Ty = read_vbr_uint(Buf, End);
+ break;
+ }
if (Ty >= CompactionTable.size())
CompactionTable.resize(Ty+1);
@@ -513,11 +527,10 @@
CompactionTable.resize(NumEntries+Type::FirstDerivedTyID);
} else {
- assert(NumEntries != 0 && "Cannot read zero entries!");
const Type *Typ = getType(Ty);
// Push the implicit zero
CompactionTable[Ty].push_back(Constant::getNullValue(Typ));
- for (unsigned i = 1; i != NumEntries; ++i) {
+ for (unsigned i = 0; i != NumEntries; ++i) {
Value *V = getGlobalTableValue(Typ, read_vbr_uint(Buf, End));
CompactionTable[Ty].push_back(V);
}
diff --git a/lib/Bytecode/Writer/Writer.cpp b/lib/Bytecode/Writer/Writer.cpp
index d0b04d2..a55508e 100644
--- a/lib/Bytecode/Writer/Writer.cpp
+++ b/lib/Bytecode/Writer/Writer.cpp
@@ -293,12 +293,24 @@
assert(StartNo < End && "Cannot emit negative range!");
assert(StartNo < Plane.size() && End <= Plane.size());
- output_vbr(unsigned(End-StartNo), Out); // Output the number of things.
- output_vbr(PlaneNo, Out); // Emit the type plane this is
-
// Do not emit the null initializer!
if (PlaneNo != Type::TypeTyID) ++StartNo;
+ // Figure out which encoding to use. By far the most common case we have is
+ // to emit 0-2 entries in a compaction table plane.
+ switch (End-StartNo) {
+ case 0: // Avoid emitting two vbr's if possible.
+ case 1:
+ case 2:
+ output_vbr((PlaneNo << 2) | End-StartNo, Out);
+ break;
+ default:
+ // Output the number of things.
+ output_vbr((unsigned(End-StartNo) << 2) | 3, Out);
+ output_vbr(PlaneNo, Out); // Emit the type plane this is
+ break;
+ }
+
for (unsigned i = StartNo; i != End; ++i)
output_vbr(Table.getGlobalSlot(Plane[i]), Out);
}