[llvm-commits] CVS: llvm/lib/VMCore/SlotCalculator.cpp

[Chris Lattner]

Changes in directory llvm/lib/VMCore:

SlotCalculator.cpp updated: 1.39 -> 1.40

---
Log message:

Check in two changes:
The first change (which is disabled) compactifies all of the function constant
pools into the global constant pool, in an attempt to reduce the amount of
duplication and overhead.  Unfortunately, as the comment indicates, this is
not yet a win, so it is disabled.

The second change sorts the typeid's so that those types that can be used
by instructions in the program appear earlier in the table than those that
cannot (such as structures and arrays).  This causes the instructions to
be able to use the dense encoding more often, saving about 5K on 254.gap.
This is only a .65% savings though, unfortunately. :(



---
Diffs of the changes:  (+51 -1)

Index: llvm/lib/VMCore/SlotCalculator.cpp
diff -u llvm/lib/VMCore/SlotCalculator.cpp:1.39 llvm/lib/VMCore/SlotCalculator.cpp:1.40
--- llvm/lib/VMCore/SlotCalculator.cpp:1.39	Fri Nov 21 14:23:48 2003
+++ llvm/lib/VMCore/SlotCalculator.cpp	Sat Jan 10 17:46:13 2004
@@ -97,6 +97,24 @@
     if (I->hasInitializer())
       getOrCreateSlot(I->getInitializer());
 
+#if 0
+  // FIXME: Empirically, this causes the bytecode files to get BIGGER, because
+  // it explodes the operand size numbers to be bigger than can be handled
+  // compactly, which offsets the ~40% savings in constant sizes.  Whoops.
+
+  // If we are emitting a bytecode file, scan all of the functions for their
+  // constants, which allows us to emit more compact modules.  This is optional,
+  // and is just used to compactify the constants used by different functions
+  // together.
+  if (!IgnoreNamedNodes) {
+    SC_DEBUG("Inserting function constants:\n");
+    for (Module::const_iterator F = TheModule->begin(), E = TheModule->end();
+         F != E; ++F)
+      for_each(constant_begin(F), constant_end(F),
+               bind_obj(this, &SlotCalculator::getOrCreateSlot));
+  }
+#endif
+
   // Insert constants that are named at module level into the slot pool so that
   // the module symbol table can refer to them...
   //
@@ -105,6 +123,38 @@
     processSymbolTable(&TheModule->getSymbolTable());
   }
 
+  // Now that we have collected together all of the information relevant to the
+  // module, compactify the type table if it is particularly big and outputting
+  // a bytecode file.  The basic problem we run into is that some programs have
+  // a large number of types, which causes the type field to overflow its size,
+  // which causes instructions to explode in size (particularly call
+  // instructions).  To avoid this behavior, we "sort" the type table so that
+  // all non-value types are pushed to the end of the type table, giving nice
+  // low numbers to the types that can be used by instructions, thus reducing
+  // the amount of explodage we suffer.
+  if (!IgnoreNamedNodes && Table[Type::TypeTyID].size() >= 64) {
+    // Scan through the type table moving value types to the start of the table.
+    TypePlane &Types = Table[Type::TypeTyID];
+    unsigned FirstNonValueTypeID = 0;
+    for (unsigned i = 0, e = Types.size(); i != e; ++i)
+      if (cast<Type>(Types[i])->isFirstClassType() ||
+          cast<Type>(Types[i])->isPrimitiveType()) {
+        // Check to see if we have to shuffle this type around.  If not, don't
+        // do anything.
+        if (i != FirstNonValueTypeID) {
+          // Swap the type ID's.
+          std::swap(Types[i], Types[FirstNonValueTypeID]);
+
+          // Keep the NodeMap up to date.
+          std::swap(NodeMap[Types[i]], NodeMap[Types[FirstNonValueTypeID]]);
+
+          // When we move a type, make sure to move its value plane as needed.
+          std::swap(Table[i], Table[FirstNonValueTypeID]);
+        }
+        ++FirstNonValueTypeID;
+      }
+  }
+
   SC_DEBUG("end processModule!\n");
 }
 
@@ -162,7 +212,7 @@
     // If there is a symbol table, it is possible that the user has names for
     // constants that are not being used.  In this case, we will have problems
     // if we don't emit the constants now, because otherwise we will get 
-    // symboltable references to constants not in the output.  Scan for these
+    // symbol table references to constants not in the output.  Scan for these
     // constants now.
     //
     processSymbolTableConstants(&F->getSymbolTable());