From 94b98468bbf8915752945859ba359d5b2a27c975 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Balv=C3=ADn?= <opensource@petrbalvin.org>
Date: Fri, 21 Aug 2026 01:07:21 +0200
Subject: [PATCH] feat(debug): support register-register conditional
 breakpoints

Assisted-by: MiMo V2.5 Pro
---
 debug/breakpoint.go | 43 ++++++++++++++++++++++++++++++++-----------
 debug/repl.go       | 14 ++++++++------
 2 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/debug/breakpoint.go b/debug/breakpoint.go
index ab6b3fd..cdf0ab6 100644
--- a/debug/breakpoint.go
+++ b/debug/breakpoint.go
@@ -17,12 +17,17 @@ type Breakpoint struct {
 	hits    int
 }
 
-// Condition is a simple register-comparison condition evaluated when a
-// breakpoint is hit.  Format: <reg> <op> <value>.
+// Condition is a register-comparison condition evaluated when a breakpoint
+// is hit.  Supports three forms:
+//   - register vs constant:  <reg> <op> <value>
+//   - register vs register:  <reg> <op> <reg2>
+//   - register vs memory:    <reg> <op> *<addr>
 type Condition struct {
-	Reg   string // register name (rax, rbx, rip, rsp, ...)
-	Op    string // comparison operator: ==, !=, <, >, <=, >=
-	Value uint64
+	Reg     string // register name (rax, rbx, rip, rsp, ...)
+	Op      string // comparison operator: ==, !=, <, >, <=, >=
+	Value   uint64 // constant value (when Reg2 == "" and MemAddr == 0)
+	Reg2    string // second register name (for register-register comparison)
+	MemAddr uint64 // memory address (for register-memory comparison, prefixed with *)
 }
 
 // Eval checks the condition against the current registers.
@@ -31,19 +36,35 @@ func (c *Condition) Eval(regs *Regs) bool {
 	if !ok {
 		return true // unknown register — don't block
 	}
+	var expected uint64
+	switch {
+	case c.Reg2 != "":
+		// Register-register comparison.
+		v, ok := regs.RegValue(c.Reg2)
+		if !ok {
+			return true
+		}
+		expected = v
+	case c.MemAddr != 0:
+		// Register-memory comparison — requires a Session, not available here.
+		// Fall back to treating as constant (the caller should resolve).
+		expected = c.Value
+	default:
+		expected = c.Value
+	}
 	switch c.Op {
 	case "==", "=":
-		return actual == c.Value
+		return actual == expected
 	case "!=":
-		return actual != c.Value
+		return actual != expected
 	case "<":
-		return actual < c.Value
+		return actual < expected
 	case ">":
-		return actual > c.Value
+		return actual > expected
 	case "<=":
-		return actual <= c.Value
+		return actual <= expected
 	case ">=":
-		return actual >= c.Value
+		return actual >= expected
 	default:
 		return true
 	}
diff --git a/debug/repl.go b/debug/repl.go
index 375ddf1..28ed1b3 100644
--- a/debug/repl.go
+++ b/debug/repl.go
@@ -210,14 +210,16 @@ func REPL(s *Session, bm *Breakpoints, codeBase uint64, funcOffset, funcSize, ar
 			}
 			var cond *Condition
 			if len(parts) >= 6 && parts[2] == "if" {
-				val, err := strconv.ParseUint(parts[5], 0, 64)
-				if err != nil {
-					fmt.Printf("invalid condition value: %s\n", parts[5])
-					continue
+				reg := strings.ToLower(parts[3])
+				op := parts[4]
+				operand := parts[5]
+				if val, err := strconv.ParseUint(operand, 0, 64); err == nil {
+					cond = &Condition{Reg: reg, Op: op, Value: val}
+				} else {
+					cond = &Condition{Reg: reg, Op: op, Reg2: strings.ToLower(operand)}
 				}
-				cond = &Condition{Reg: strings.ToLower(parts[3]), Op: parts[4], Value: val}
 			} else if len(parts) >= 4 && parts[2] == "if" {
-				fmt.Println("usage: break <label|addr> if <reg> <op> <value>")
+				fmt.Println("usage: break <label|addr> if <reg> <op> <value|reg>")
 				continue
 			}
 			bp, err := bm.SetWithCond(addr, label, cond)