[liftoff] Skip unreachable breakpoints

Forward the breakpoint iterator to the current position, ignoring
unreachable breakpoints.

R=clemensb@chromium.org

Bug: v8:10147
Change-Id: Ic7e7fca4c69fdea68676ff75031bb5133bfc69d9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100993
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66716}

src/wasm/baseline/liftoff-compiler.cc

@@ -633,10 +633,6 @@ class LiftoffCompiler {
   }
 
   void FinishFunction(FullDecoder* decoder) {
-    // All breakpoints (if any) must be emitted by now.
-    DCHECK(next_breakpoint_ptr_ == nullptr ||
-           (*next_breakpoint_ptr_ == 0 &&
-            next_breakpoint_ptr_ + 1 == next_breakpoint_end_));
     if (DidAssemblerBailout(decoder)) return;
     for (OutOfLineCode& ool : out_of_line_code_) {
       GenerateOutOfLineCode(&ool);
@@ -662,13 +658,17 @@ class LiftoffCompiler {
         // A single breakpoint at offset 0 indicates stepping.
         DCHECK_EQ(next_breakpoint_ptr_ + 1, next_breakpoint_end_);
         EmitBreakpoint(decoder);
-      } else if (*next_breakpoint_ptr_ == decoder->position()) {
-        ++next_breakpoint_ptr_;
-        // TODO(thibaudm): skip unreachable breakpoints.
+      } else {
+        while (next_breakpoint_ptr_ != next_breakpoint_end_ &&
+               *next_breakpoint_ptr_ < decoder->position()) {
+          // Skip unreachable breakpoints.
+          ++next_breakpoint_ptr_;
+        }
         if (next_breakpoint_ptr_ == next_breakpoint_end_) {
           next_breakpoint_ptr_ = next_breakpoint_end_ = nullptr;
+        } else if (*next_breakpoint_ptr_ == decoder->position()) {
+          EmitBreakpoint(decoder);
         }
-        EmitBreakpoint(decoder);
       }
     }
     TraceCacheState(decoder);

test/inspector/debugger/wasm-set-breakpoint-liftoff-expected.txt

@@ -18,6 +18,8 @@ at wasm_B (0:56):
 at (anonymous) (0:17):
    -- skipped
 Setting breakpoint at offset 39 on script v8://test/runWasm
+Setting breakpoint at offset 61 on script v8://test/runWasm
+Setting breakpoint at offset 60 on script v8://test/runWasm
 Setting breakpoint at offset 54 on script v8://test/runWasm
 Setting breakpoint at offset 53 on script v8://test/runWasm
 Setting breakpoint at offset 51 on script v8://test/runWasm
@@ -322,5 +324,15 @@ at wasm_B (0:47):
    stack: "0": -11 (number)
 at (anonymous) (0:17):
    -- skipped
+Paused:
+Script wasm://wasm/0c10a5fe byte offset 61: Wasm opcode 0xb
+Scope:
+at wasm_B (0:61):
+ - scope (global):
+ - scope (local):
+   locals: "var0": 0 (number)
+   stack: 
+at (anonymous) (0:17):
+   -- skipped
 exports.main returned!
 Finished!

test/inspector/debugger/wasm-set-breakpoint-liftoff.js

@@ -95,7 +95,8 @@ Protocol.Debugger.onPaused(async msg => {
     // Check that setting breakpoints on active instances of A and B takes
     // effect immediately.
     setBreakpoint(func_a.body_offset + 1, loc.scriptId, frame.url);
-    for (offset of [11, 10, 8, 6, 2, 4]) {
+    // All of the following breakpoints are in reachable code, except offset 17.
+    for (offset of [18, 17, 11, 10, 8, 6, 2, 4]) {
       setBreakpoint(func_b.body_offset + offset, loc.scriptId, frame.url);
     }
     first_iteration = false;