From fe6b2b898aee944ba3490c35f4aed4d155485c0e Mon Sep 17 00:00:00 2001
From: iximeow <me@iximeow.net>
Date: Mon, 25 May 2026 19:21:31 +0000
Subject: push/pop width in 16/32-bit modes are receptive to operand width
 prefix

---
 src/real_mode/behavior.rs | 68 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

(limited to 'src/real_mode/behavior.rs')

diff --git a/src/real_mode/behavior.rs b/src/real_mode/behavior.rs
index 8941ee5..7724a0a 100644
--- a/src/real_mode/behavior.rs
+++ b/src/real_mode/behavior.rs
@@ -140,6 +140,16 @@ impl Instruction {
                         .set_operand(1, Access::Read)
                         .set_operand(2, Access::Read);
                 }
+            } else if self.opcode == Opcode::PUSH {
+               if self.prefixes.operand_size() {
+                   behavior = behavior
+                       .set_implicit_ops(PUSHW_OPS_IDX);
+               }
+            } else if self.opcode == Opcode::PUSHF {
+               if self.prefixes.operand_size() {
+                   behavior = behavior
+                       .set_implicit_ops(PUSHFW_OPS_IDX);
+               }
             } else if self.opcode == Opcode::DIV || self.opcode == Opcode::IDIV {
                 let op_width = if self.operands[0] == OperandSpec::RegMMM {
                     self.regs[1].width()
@@ -1960,6 +1970,28 @@ static PUSH_OPS: &'static [ImplicitOperand] = &[
     }
 ];
 
+static PUSHW_OPS: &'static [ImplicitOperand] = &[
+    ImplicitOperand {
+        spec: OperandSpec::Disp,
+        reg: RegSpec::sp(),
+        disp: -4i32,
+        write: true,
+    },
+    // push.. pushes the value (above), then does a RMW on rsp.
+    ImplicitOperand {
+        spec: OperandSpec::RegRRR,
+        reg: RegSpec::sp(),
+        disp: 0,
+        write: false,
+    },
+    ImplicitOperand {
+        spec: OperandSpec::RegRRR,
+        reg: RegSpec::sp(),
+        disp: 0,
+        write: true,
+    }
+];
+
 static POP_OPS: &'static [ImplicitOperand] = &[
     ImplicitOperand {
         spec: OperandSpec::Deref,
@@ -2127,6 +2159,34 @@ static PUSHF_OPS: &'static [ImplicitOperand] = &[
     }
 ];
 
+static PUSHFW_OPS: &'static [ImplicitOperand] = &[
+    ImplicitOperand {
+        spec: OperandSpec::RegRRR,
+        reg: RegSpec::eflags(),
+        disp: 0,
+        write: false,
+    },
+    ImplicitOperand {
+        spec: OperandSpec::Disp,
+        reg: RegSpec::sp(),
+        disp: -4i32,
+        write: true,
+    },
+    // push.. pushes the value (above), then does a RMW on rsp.
+    ImplicitOperand {
+        spec: OperandSpec::RegRRR,
+        reg: RegSpec::sp(),
+        disp: 0,
+        write: false,
+    },
+    ImplicitOperand {
+        spec: OperandSpec::RegRRR,
+        reg: RegSpec::sp(),
+        disp: 0,
+        write: true,
+    }
+];
+
 static POPF_OPS: &'static [ImplicitOperand] = &[
     ImplicitOperand {
         spec: OperandSpec::Deref,
@@ -3689,8 +3749,10 @@ const PUSHA_IDX: u16 = 72;
 const POPA_IDX: u16 = 73;
 const PUSHAD_IDX: u16 = 74;
 const POPAD_IDX: u16 = 75;
+const PUSHW_OPS_IDX: u16 = 76;
+const PUSHFW_OPS_IDX: u16 = 77;
 
-static IMPLICIT_OPS_LIST: [&[ImplicitOperand]; 76] = [
+static IMPLICIT_OPS_LIST: [&[ImplicitOperand]; 78] = [
     &[], // implicit ops list 0 is not used
     PUSH_OPS,
     POP_OPS,
@@ -3767,6 +3829,8 @@ static IMPLICIT_OPS_LIST: [&[ImplicitOperand]; 76] = [
     POPA_OPS,
     PUSHAD_OPS,
     POPAD_OPS,
+    PUSHW_OPS,
+    PUSHFW_OPS,
 ];
 
 fn opcode2behavior(opc: &Opcode) -> BehaviorDigest {
@@ -3910,6 +3974,7 @@ static TABLE: [BehaviorDigest; 1428] = [
             .set_operand(0, Access::Read),
     /* PUSH => */ BehaviorDigest::empty()
             .set_implicit_ops(PUSH_OPS_IDX)
+            .set_nontrivial(true)
             .set_pl_any()
             .set_operand(0, Access::Read),
     /* POP => */ BehaviorDigest::empty()
@@ -3957,6 +4022,7 @@ static TABLE: [BehaviorDigest; 1428] = [
             .set_pl_any(),
     /* PUSHF => */ BehaviorDigest::empty()
             .set_implicit_ops(PUSHF_IDX)
+            .set_nontrivial(true)
             .set_pl_any(),
     /* WAIT => */ GENERAL,
     /* CBW => */ BehaviorDigest::empty()
-- 
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