From b73da4ed02f08610e98d9b343286d5c5710629a2 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Tue, 31 Mar 2020 23:52:46 +0200
Subject: [PATCH] some more obvious optimizations for X+X and X-X

---
 compiler/res/prog8lib/prog8lib.asm            |  2 --
 compiler/src/prog8/compiler/Main.kt           |  3 +++
 .../prog8/optimizer/ExpressionSimplifier.kt   | 13 ++++++++++
 examples/test.p8                              | 24 -------------------
 4 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/compiler/res/prog8lib/prog8lib.asm b/compiler/res/prog8lib/prog8lib.asm
index 06c194880..f69e10787 100644
--- a/compiler/res/prog8lib/prog8lib.asm
+++ b/compiler/res/prog8lib/prog8lib.asm
@@ -1772,7 +1772,6 @@ _loop_hi	ldy  _index_first
 
 ror2_mem_ub	.proc
 		; -- in-place 8-bit ror of byte at memory location on stack
-		; TODO use self modifying code here
 		inx
 		lda  c64.ESTACK_LO,x
 		sta  c64.SCRATCH_ZPWORD1
@@ -1789,7 +1788,6 @@ ror2_mem_ub	.proc
 
 rol2_mem_ub	.proc
 		; -- in-place 8-bit rol of byte at memory location on stack
-		; TODO use self modifying code here
 		inx
 		lda  c64.ESTACK_LO,x
 		sta  c64.SCRATCH_ZPWORD1
diff --git a/compiler/src/prog8/compiler/Main.kt b/compiler/src/prog8/compiler/Main.kt
index 95a47dc58..5442c6c66 100644
--- a/compiler/src/prog8/compiler/Main.kt
+++ b/compiler/src/prog8/compiler/Main.kt
@@ -165,6 +165,9 @@ private fun optimizeAst(programAst: Program, errors: ErrorReporter) {
         if (optsDone1 + optsDone2 == 0)
             break
     }
+    // because simplified statements and expressions could give rise to more constants that can be folded away:
+    programAst.constantFold(errors)
+    errors.handle()
 }
 
 private fun postprocessAst(programAst: Program, errors: ErrorReporter, compilerOptions: CompilationOptions) {
diff --git a/compiler/src/prog8/optimizer/ExpressionSimplifier.kt b/compiler/src/prog8/optimizer/ExpressionSimplifier.kt
index ea491f206..0238b7e26 100644
--- a/compiler/src/prog8/optimizer/ExpressionSimplifier.kt
+++ b/compiler/src/prog8/optimizer/ExpressionSimplifier.kt
@@ -258,6 +258,14 @@ internal class ExpressionSimplifier(private val program: Program) : AstWalker()
     }
 
     private fun optimizeAdd(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if(expr.left.isSameAs(expr.right)) {
+            // optimize X+X into X *2
+            expr.operator = "*"
+            expr.right = NumericLiteralValue.optimalInteger(2, expr.right.position)
+            expr.right.linkParents(expr)
+            return expr
+        }
+
         if (leftVal == null && rightVal == null)
             return null
 
@@ -278,6 +286,11 @@ internal class ExpressionSimplifier(private val program: Program) : AstWalker()
     }
 
     private fun optimizeSub(expr: BinaryExpression, leftVal: NumericLiteralValue?, rightVal: NumericLiteralValue?): Expression? {
+        if(expr.left.isSameAs(expr.right)) {
+            // optimize X-X into 0
+            return NumericLiteralValue.optimalInteger(0, expr.position)
+        }
+
         if (leftVal == null && rightVal == null)
             return null
 
diff --git a/examples/test.p8 b/examples/test.p8
index 0dc0be01b..742945455 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,33 +1,9 @@
 %import c64lib
 %import c64utils
-%zeropage dontuse
 
 
 main {
     sub start() {
-        ubyte ub
-        byte bb
-        word ww
-        uword uw
-        uword auw
-        word aww
-        byte ab
-        ubyte aub
-
-        ; TODO optimize all of these:
-        ab = bb+bb      ; TODO bb * 2?  (bb<<1)
-        ab = bb+bb+bb
-        aww = ww+ww
-        aww = ww+ww+ww
-
-        aub = ub+ub
-        aub = ub+ub+ub
-        auw = uw+uw
-        auw = uw+uw+uw
-
-
-        A = A+A
-        Y=Y+Y+Y
 
     }
 }