From 0698dd72ea3b9d7897e63c6e219061bff8d162cf Mon Sep 17 00:00:00 2001
From: Damien George <damien@micropython.org>
Date: Fri, 11 Nov 2022 12:25:32 +1100
Subject: [PATCH] py/emitnative: Ensure load_subscr does not clobber existing
 REG_ARG_2.

Follow up from a similar fix in 426785a19eeb12aef7383fbda4693575d8c4dddf

Fixes issue #6314.

Signed-off-by: Damien George <damien@micropython.org>
---
 py/emitnative.c                             |  3 +++
 tests/micropython/viper_subscr_multi.py     | 17 +++++++++++++----
 tests/micropython/viper_subscr_multi.py.exp |  1 +
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/py/emitnative.c b/py/emitnative.c
index 7e98ba1556..2d694983bd 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -1527,6 +1527,7 @@ STATIC void emit_native_load_subscr(emit_t *emit) {
                             break;
                         }
                         #endif
+                        need_reg_single(emit, reg_index, 0);
                         ASM_MOV_REG_IMM(emit->as, reg_index, index_value);
                         ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add index to base
                         reg_base = reg_index;
@@ -1544,6 +1545,7 @@ STATIC void emit_native_load_subscr(emit_t *emit) {
                             break;
                         }
                         #endif
+                        need_reg_single(emit, reg_index, 0);
                         ASM_MOV_REG_IMM(emit->as, reg_index, index_value << 1);
                         ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add 2*index to base
                         reg_base = reg_index;
@@ -1561,6 +1563,7 @@ STATIC void emit_native_load_subscr(emit_t *emit) {
                             break;
                         }
                         #endif
+                        need_reg_single(emit, reg_index, 0);
                         ASM_MOV_REG_IMM(emit->as, reg_index, index_value << 2);
                         ASM_ADD_REG_REG(emit->as, reg_index, reg_base); // add 4*index to base
                         reg_base = reg_index;
diff --git a/tests/micropython/viper_subscr_multi.py b/tests/micropython/viper_subscr_multi.py
index 1561e5534d..a2baba2411 100644
--- a/tests/micropython/viper_subscr_multi.py
+++ b/tests/micropython/viper_subscr_multi.py
@@ -6,15 +6,24 @@ def f1(b: ptr8):
     b[0] += b[1]
 
 
+b = bytearray(b"\x01\x02")
+f1(b)
+print(b)
+
+
 @micropython.viper
 def f2(b: ptr8, i: int):
     b[0] += b[i]
 
 
-b = bytearray(b"\x01\x02")
-f1(b)
-print(b)
-
 b = bytearray(b"\x01\x02")
 f2(b, 1)
 print(b)
+
+
+@micropython.viper
+def f3(b: ptr8) -> int:
+    return b[0] << 24 | b[1] << 16 | b[2] << 8 | b[3]
+
+
+print(hex(f3(b"\x01\x02\x03\x04")))
diff --git a/tests/micropython/viper_subscr_multi.py.exp b/tests/micropython/viper_subscr_multi.py.exp
index a2c298bb16..ea644c046d 100644
--- a/tests/micropython/viper_subscr_multi.py.exp
+++ b/tests/micropython/viper_subscr_multi.py.exp
@@ -1,2 +1,3 @@
 bytearray(b'\x03\x02')
 bytearray(b'\x03\x02')
+0x1020304