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authorKartik Agaram <vc@akkartik.com>2020-09-08 22:47:30 -0700
committerKartik Agaram <vc@akkartik.com>2020-09-08 22:48:47 -0700
commit6b36e4dbc7749addeebe523992e0bcb62ad6b2d5 (patch)
treee041a9099e170c84c23a352d92fcf8efd536d788 /302stack_allocate.subx
parentd9a05dfbb7ac73b31b1f3c1fb36a5324243da8a2 (diff)
downloadmu-6b36e4dbc7749addeebe523992e0bcb62ad6b2d5.tar.gz
6760
Fix a couple of subtle bugs.

- the VM was conditionally reading from the instruction stream, so that
  other bugs got masked by decoding errors.
- push-n-bytes was clobbering eax.
Diffstat (limited to '302stack_allocate.subx')
-rw-r--r--302stack_allocate.subx13
1 files changed, 6 insertions, 7 deletions
diff --git a/302stack_allocate.subx b/302stack_allocate.subx
index 02ad84f2..4634039d 100644
--- a/302stack_allocate.subx
+++ b/302stack_allocate.subx
@@ -37,15 +37,12 @@ $push-n-zero-bytes:prologue:
     89/<- %ebp 4/r32/esp
 $push-n-zero-bytes:copy-ra:
     # -- esp = ebp
-    50/push-eax
-    # -- esp+8 = ebp+4
-    # -- esp+4 = ebp
-    8b/-> *(esp+4) 0/r32/eax
+    89/<- *Push-n-zero-bytes-eax 0/r32/eax
+    8b/-> *esp 0/r32/eax
     2b/subtract *(ebp+4) 4/r32/esp
-    # -- esp+4+n = ebp
-    89/<- *(esp+4) 0/r32/eax
-    58/pop-to-eax
     # -- esp+n = ebp
+    89/<- *esp 0/r32/eax
+    8b/-> *Push-n-zero-bytes-eax 0/r32/eax
 $push-n-zero-bytes:bulk-cleaning:
     89/<- *Push-n-zero-bytes-esp 4/r32/esp
     81 0/subop/add *Push-n-zero-bytes-esp 4/imm32
@@ -60,3 +57,5 @@ Push-n-zero-bytes-ebp:  # (addr int)
   0/imm32
 Push-n-zero-bytes-esp:  # (addr int)
   0/imm32
+Push-n-zero-bytes-eax:
+  0/imm32