report memory sizes for push, pop, call, ret

these instructions had memory sizes reported for the operand, if it was
a memory operand, but for versions with non-memory operands the decoded
`Instruction` would imply that non memory access would happen at all.
now, decoded instructions in these cases will report a more useful
memory size.

2 files changed, 23 insertions, 0 deletions

diff --git a/test/real_mode/mod.rs b/test/real_mode/mod.rs
index 6005f07..8543fae 100644
--- a/test/real_mode/mod.rs
+++ b/test/real_mode/mod.rs
@@ -1,3 +1,5 @@
+mod operand;
+
 use std::fmt::Write;
 
 use yaxpeax_arch::{AddressBase, Decoder, U8Reader, LengthedInstruction};
@@ -17892,6 +17894,7 @@ fn test_real_mode() {
     test_display(&[0xff, 0x08], "dec word [bx + si]");
     test_display(&[0xff, 0x15], "call word [di]");
     test_display(&[0x67, 0xff, 0x15, 0x12, 0x12, 0x12, 0x12], "call word [0x12121212]");
+    // note that this call only writes two bytes, and only moves sp by two.
     test_display(&[0x66, 0xff, 0x15], "call dword [di]");
     test_display(&[0xff, 0x18], "callf dword [bx + si]");
     test_display(&[0xff, 0x24], "jmp word [si]");
diff --git a/test/real_mode/operand.rs b/test/real_mode/operand.rs
new file mode 100644
index 0000000..e037fee
--- /dev/null
+++ b/test/real_mode/operand.rs
@@ -0,0 +1,20 @@
+use yaxpeax_x86::real_mode::{InstDecoder, Operand, RegSpec};
+use yaxpeax_x86::MemoryAccessSize;
+
+#[test]
+fn test_implied_memory_width() {
+    fn mem_size_of(data: &[u8]) -> Option<u8> {
+        let decoder = InstDecoder::default();
+        decoder.decode_slice(data).unwrap().mem_size().unwrap().bytes_size()
+    }
+
+    // test push, pop, call, and ret
+    assert_eq!(mem_size_of(&[0xc3]), Some(2));
+    assert_eq!(mem_size_of(&[0xe8, 0x11, 0x22, 0x33, 0x44]), Some(2));
+    assert_eq!(mem_size_of(&[0x50]), Some(2));
+    assert_eq!(mem_size_of(&[0x58]), Some(2));
+    assert_eq!(mem_size_of(&[0x66, 0x50]), Some(2));
+    assert_eq!(mem_size_of(&[0x66, 0x58]), Some(2));
+    assert_eq!(mem_size_of(&[0xff, 0xf0]), Some(2));
+    assert_eq!(mem_size_of(&[0x66, 0xff, 0xf0]), Some(4));
+}