From fb041f75e5a78111e6fad4cc6ccd3b2cb38c5dd3 Mon Sep 17 00:00:00 2001
From: Tillmann Karras <tilkax@gmail.com>
Date: Tue, 2 Jun 2020 01:50:02 +0100
Subject: [PATCH] DSPSpy: save and restore $sr properly

---
 Source/DSPSpy/gba.txt            | 38 ++++++++++++++++----------------
 Source/DSPSpy/tests/dsp_base.inc | 22 +++++++-----------
 Source/DSPSpy/tests/dsp_test.ds  |  3 ---
 3 files changed, 27 insertions(+), 36 deletions(-)

diff --git a/Source/DSPSpy/gba.txt b/Source/DSPSpy/gba.txt
index d4f1a9c333..48c1a13ab6 100644
--- a/Source/DSPSpy/gba.txt
+++ b/Source/DSPSpy/gba.txt
@@ -33,7 +33,7 @@ m0
 clr15       
 
 ;step 1: context setup
-call		send_back_40
+call		send_back
 
 call        0x807e			; loop until DSP->CPU mailbox is empty
 si          @DMBH, #0xdcd1
@@ -342,44 +342,44 @@ call		send_back
 
 call		send_back
 set40       
-call		send_back_40
+call		send_back
 lri         $AR2, #0x0015
-call		send_back_40
+call		send_back
 lr          $AC0.M, @0x0006
-call		send_back_40
+call		send_back
 lr          $AX0.H, @0x165b
-call		send_back_40
+call		send_back
 call        0x88e5
-call		send_back_40
+call		send_back
 asr         $ACC0, #-3
-call		send_back_40
+call		send_back
 lsl         $ACC0, #3
-call		send_back_40
+call		send_back
 srri        @$AR2, $AC0.M
-call		send_back_40
+call		send_back
 srri        @$AR2, $AC0.L
-call		send_back_40
+call		send_back
 lri         $AR2, #0x0016
-call		send_back_40
+call		send_back
 lr          $AC0.M, @0x1723
-call		send_back_40
+call		send_back
 asr         $ACC0, #-12
-call		send_back_40
+call		send_back
 lr          $AX0.H, @0x166b
-call		send_back_40
+call		send_back
 call        0x88e5
-call		send_back_40
+call		send_back
 tst         $ACC0
-call		send_back_40
+call		send_back
 jge         Unk_012e
-call		send_back_40
+call		send_back
 
 clr         $ACC0
-call		send_back_40
+call		send_back
 
 Unk_012e:
 asr         $ACC0, #-3
-call		send_back_40
+call		send_back
 set16       
 ;step 4
 call		send_back
diff --git a/Source/DSPSpy/tests/dsp_base.inc b/Source/DSPSpy/tests/dsp_base.inc
index 7fac883311..c890390314 100644
--- a/Source/DSPSpy/tests/dsp_base.inc
+++ b/Source/DSPSpy/tests/dsp_base.inc
@@ -169,10 +169,9 @@ irq:
 
 ; DMA:s the current state of the registers back to the PowerPC. To do this,
 ; it must write the contents of all regs to DRAM.
-; Unfortunately, this loop uses ar0 so it's best to use AR1 and friends for testing
-; when messing with indexing.
 send_back:
-	; make state safe.
+	; first, store $sr so we can modify it
+	sr	@(REGS_BASE + 19), $sr
 	set16
 	; store registers to reg table
 	sr		@REGS_BASE,  $ar0
@@ -195,7 +194,8 @@ send_back:
 	srri	@$ar0, $ac0.h
 	srri	@$ar0, $ac1.h
 	srri	@$ar0, $cr
-	srri	@$ar0, $sr
+	; skip $sr since we already stored and modified it
+	iar	$ar0
 	srri	@$ar0, $prod.l
 	srri	@$ar0, $prod.m1
 	srri	@$ar0, $prod.h
@@ -257,7 +257,8 @@ dma_copy:
 	lrri	$ac0.h, @$ar0
 	lrri	$ac1.h, @$ar0
 	lrri	$cr, @$ar0
-	lrri	$sr, @$ar0
+	; leave $sr for later
+	iar	$ar0
 	lrri	$prod.l, @$ar0
 	lrri	$prod.m1, @$ar0
 	lrri	$prod.h, @$ar0
@@ -270,17 +271,10 @@ dma_copy:
 	lrri	$ac1.l, @$ar0
 	lrri	$ac0.m, @$ar0
 	lrri	$ac1.m, @$ar0
-	lr		$ar0, @REGS_BASE
+	lr	$ar0, @REGS_BASE
+	lr	$sr, @(REGS_BASE+19)
 
 	ret		; from send_back
 
-; If you are in set40 mode, use this instead of send_back if you want to stay
-; in set40 mode.
-send_back_40:
-	set16
-	call	send_back
-	set40
-	ret
-
 ; Obviously this must be included directly before your test code
 start_of_test:
diff --git a/Source/DSPSpy/tests/dsp_test.ds b/Source/DSPSpy/tests/dsp_test.ds
index 818f681567..3550dd205c 100644
--- a/Source/DSPSpy/tests/dsp_test.ds
+++ b/Source/DSPSpy/tests/dsp_test.ds
@@ -6,9 +6,6 @@ include "dsp_base.inc"
         
 ;  We can call send_back at any time to send data back to the PowerPC.
 
-;  Calling set40 here seemed to crash the dsp tester in strange ways
-;  until I added set16 in send_back. Seems clear that it affects something important.
-
        lri $AC0.M, #0x1000	
 	call send_back