From 08d9c148d0d4c3f12f547b04786a6738c02731dc Mon Sep 17 00:00:00 2001
From: James Roseborough <james.roseborough@luaj.org>
Date: Fri, 30 Jul 2010 23:50:03 +0000
Subject: [PATCH] Improve bytecode generation.

---
 src/jse/org/luaj/vm2/luajc/Slots.java | 30 ++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/jse/org/luaj/vm2/luajc/Slots.java b/src/jse/org/luaj/vm2/luajc/Slots.java
index 15edaa10..2933e7a8 100644
--- a/src/jse/org/luaj/vm2/luajc/Slots.java
+++ b/src/jse/org/luaj/vm2/luajc/Slots.java
@@ -333,13 +333,15 @@ public class Slots {
 	}
 
 	private void markuninitialized() {
-		for ( int j=p.numparams; j<m; j++ )
-			if ( ! isreferrededtofirst(j) )
+		for ( int j=p.numparams; j<m; j++ ) 
+			if ( ! needsinitialnil(j) )
 				slots[0][j] |= BIT_INVALID;
 	}
 	
-	private boolean isreferrededtofirst(int j) {
+	private boolean needsinitialnil(int j) {
 		for ( int i=1; i<=n; i++ ) {
+			if ( isbranchsource(i) )
+				return true;
 			if ( (slots[i][j] & (BIT_REFER | BIT_UP_REFER)) != 0 )
 				return true;
 			if ( (slots[i][j] & (BIT_ASSIGN | BIT_UP_ASSIGN | BIT_UP_CREATE | BIT_INVALID)) != 0 )
@@ -348,6 +350,28 @@ public class Slots {
 		return false;
 	}
 
+	private boolean isbranchsource(int index) {
+		if (index >= p.code.length )
+			return false;
+		int ins = p.code[index];
+		switch ( Lua.GET_OPCODE(ins) ) {			
+		case Lua.OP_LOADBOOL:
+			if ( Lua.GETARG_C(ins) == 0 )
+				return true;
+		case Lua.OP_EQ:
+		case Lua.OP_LT:
+		case Lua.OP_LE:
+		case Lua.OP_TEST: 
+		case Lua.OP_TESTSET:
+		case Lua.OP_TFORLOOP: 
+		case Lua.OP_JMP:
+		case Lua.OP_FORPREP:
+		case Lua.OP_FORLOOP:
+			return true;
+		}
+		return false;
+	}
+	
 	private void markupvalues( ) {
 		for ( int pc=0; pc<n; ++pc ) {
 			if ( Lua.GET_OPCODE(p.code[pc]) == Lua.OP_CLOSURE ) {