From ead8aa780024fe12ecc51e7f154583695feef629 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 29 Jun 2024 17:22:57 +0200
Subject: [PATCH]  asm optimization: bxx+jmp -> opposite bxx

---
 .../src/prog8/codegen/cpu6502/AsmOptimizer.kt | 83 +++++++++++++++----
 docs/source/todo.rst                          | 11 ---
 2 files changed, 66 insertions(+), 28 deletions(-)

diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmOptimizer.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmOptimizer.kt
index 487ae797a..c820e49ab 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmOptimizer.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmOptimizer.kt
@@ -446,23 +446,6 @@ private fun optimizeStoreLoadSame(
             if (firstLoc == secondLoc)
                 mods.add(Modification(lines[2].index, true, null))
         }
-
-        // phy + ldy + pla -> tya + ldy
-        // phx + ldx + pla -> txa + ldx
-        // pha + lda + pla -> nop
-        if(first=="phy" && second.startsWith("ldy ") && third=="pla") {
-            mods.add(Modification(lines[3].index, true, null))
-            mods.add(Modification(lines[1].index, false, "  tya"))
-        }
-        else if(first=="phx" && second.startsWith("ldx ") && third=="pla") {
-            mods.add(Modification(lines[3].index, true, null))
-            mods.add(Modification(lines[1].index, false, "  txa"))
-        }
-        else if(first=="pha" && second.startsWith("lda ") && third=="pla") {
-            mods.add(Modification(lines[1].index, true, null))
-            mods.add(Modification(lines[2].index, true, null))
-            mods.add(Modification(lines[3].index, true, null))
-        }
     }
     return mods
 }
@@ -525,6 +508,7 @@ private fun optimizeJsrRtsAndOtherCombinations(linesByFour: Sequence<List<Indexe
     for (lines in linesByFour) {
         val first = lines[0].value
         val second = lines[1].value
+        val third = lines[2].value
         if ((" jsr" in first || "\tjsr" in first ) && (" rts" in second || "\trts" in second)) {
             mods += Modification(lines[0].index, false, lines[0].value.replace("jsr", "jmp"))
             mods += Modification(lines[1].index, true, null)
@@ -594,6 +578,48 @@ private fun optimizeJsrRtsAndOtherCombinations(linesByFour: Sequence<List<Indexe
                 mods += Modification(lines[3].index, true, null)
             }
         }
+
+
+        fun sameLabel(branchInstr: String, jumpInstr: String, labelInstr: String): Boolean {
+            if('(' in jumpInstr) return false       // indirect jump cannot be replaced
+            val label = labelInstr.trimEnd().substringBefore(':').substringBefore(' ').substringBefore('\t')
+            println("label=$label")
+            return true
+        }
+
+        // beq Label + jmp Addr + Label  -> bne Addr
+        if((" jmp" in second || "\tjmp " in second) && haslabel(third)) {
+            if((" beq " in first || "\tbeq " in first) && sameLabel(first, second, third)) {
+                val branch = second.replace("jmp", "bne")
+                mods.add(Modification(lines[0].index, true, null))
+                mods.add(Modification(lines[1].index, false, branch))
+            }
+            else if((" bne " in first || "\tbne " in first) && sameLabel(first, second, third)) {
+                val branch = second.replace("jmp", "beq")
+                mods.add(Modification(lines[0].index, true, null))
+                mods.add(Modification(lines[1].index, false, branch))
+            }
+            else if((" bcc " in first || "\tbcc " in first) && sameLabel(first, second, third)){
+                val branch = second.replace("jmp", "bcs")
+                mods.add(Modification(lines[0].index, true, null))
+                mods.add(Modification(lines[1].index, false, branch))
+            }
+            else if((" bcs " in first || "\tbcs " in first) && sameLabel(first, second, third)) {
+                val branch = second.replace("jmp", "bcc")
+                mods.add(Modification(lines[0].index, true, null))
+                mods.add(Modification(lines[1].index, false, branch))
+            }
+            else if((" bpl " in first || "\tbpl " in first) && sameLabel(first, second, third)) {
+                val branch = second.replace("jmp", "bmi")
+                mods.add(Modification(lines[0].index, true, null))
+                mods.add(Modification(lines[1].index, false, branch))
+            }
+            else if((" bmi " in first || "\tbmi " in first) && sameLabel(first, second, third)) {
+                val branch = second.replace("jmp", "bpl")
+                mods.add(Modification(lines[0].index, true, null))
+                mods.add(Modification(lines[1].index, false, branch))
+            }
+        }
     }
     return mods
 }
@@ -631,7 +657,30 @@ private fun optimizeUselessPushPopStack(linesByFour: Sequence<List<IndexedValue<
         optimize('a', lines)
         optimize('x', lines)
         optimize('y', lines)
+
+        val first = lines[1].value.trimStart()
+        val second = lines[2].value.trimStart()
+        val third = lines[3].value.trimStart()
+
+        // phy + ldy + pla -> tya + ldy
+        // phx + ldx + pla -> txa + ldx
+        // pha + lda + pla -> nop
+        if(first=="phy" && second.startsWith("ldy ") && third=="pla") {
+            mods.add(Modification(lines[3].index, true, null))
+            mods.add(Modification(lines[1].index, false, "  tya"))
+        }
+        else if(first=="phx" && second.startsWith("ldx ") && third=="pla") {
+            mods.add(Modification(lines[3].index, true, null))
+            mods.add(Modification(lines[1].index, false, "  txa"))
+        }
+        else if(first=="pha" && second.startsWith("lda ") && third=="pla") {
+            mods.add(Modification(lines[1].index, true, null))
+            mods.add(Modification(lines[2].index, true, null))
+            mods.add(Modification(lines[3].index, true, null))
+        }
     }
+
+
     return mods
 }
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 69f5e5e25..e8a3abc6f 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -6,17 +6,6 @@ causes compiler error for virtual: just calling txt.cls() gives compile error un
 
 https://github.com/irmen/prog8/issues/136 (string.find register order issue)
 
-if-optimization:
-        if row == NUMQUEENS {
-            print_solution()
-            return
-        }
- compiles into this, where the bne+jmp could be a single beq instead:
-	cmp  #8
-	bne  label_asm_21_afterif
-	jmp  p8b_main.p8s_print_solution
-label_asm_21_afterif:
-
 
 optimize signed byte/word division by powers of 2 (and shift right?), it's now using divmod routine.  (also % ?)
     see inplacemodificationByteVariableWithLiteralval() and inplacemodificationSomeWordWithLiteralval()