From 73dfb5f4435da2b30aac79af53bff3657c6906ac Mon Sep 17 00:00:00 2001
From: Natt Akuma <akumanatt925@gmail.com>
Date: Fri, 4 Feb 2022 00:59:44 +0700
Subject: [PATCH] Optimize sign extension to AY

---
 codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt |  8 +++++++-
 compiler/res/prog8lib/prog8_lib.asm                | 14 --------------
 2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
index d85bca51a..b146fe260 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
@@ -1707,7 +1707,13 @@ $repeatLabel    lda  $counterVar
         // sign extend signed byte in A to full word in AY
         when(valueDt) {
             DataType.UBYTE -> out("  ldy  #0")
-            DataType.BYTE -> out("  jsr  prog8_lib.sign_extend_AY_byte")
+            DataType.BYTE -> out("""
+                ldy  #0
+                cmp  #$80
+                bcc  +
+                dey
++
+            """)
             else -> throw AssemblyError("need byte type")
         }
     }
diff --git a/compiler/res/prog8lib/prog8_lib.asm b/compiler/res/prog8lib/prog8_lib.asm
index 3b87301af..acbbaf41c 100644
--- a/compiler/res/prog8lib/prog8_lib.asm
+++ b/compiler/res/prog8lib/prog8_lib.asm
@@ -1158,20 +1158,6 @@ sign_extend_stack_byte	.proc
 		rts
 		.pend
 
-
-sign_extend_AY_byte	.proc
-	; -- sign extend the (signed) byte in AY to full 16 bits
-		pha
-		and  #$80
-		beq  +
-		ldy  #$ff
-		pla
-		rts
-+		ldy  #0
-		pla
-		rts
-		.pend
-
 strlen          .proc
         ; -- returns the number of bytes in the string in AY, in Y.
 		sta  P8ZP_SCRATCH_W1