Debugging: add debug-tags to instrumented trap sites so we actually get PCs on traps.

crates/cranelift/src/func_environ.rs

@@ -1391,6 +1391,10 @@ impl TranslateTrap for FuncEnvironment<'_> {
     ) -> ir::FuncRef {
         self.builtin_functions.load_builtin(builder.func, index)
     }
+
+    fn debug_tags(&self, srcloc: ir::SourceLoc) -> Vec<ir::DebugTag> {
+        FuncEnvironment::debug_tags(self, srcloc)
+    }
 }
 
 #[derive(Default)]

crates/cranelift/src/trap.rs

@@ -20,6 +20,9 @@ pub trait TranslateTrap {
         builder: &mut FunctionBuilder<'_>,
         index: BuiltinFunctionIndex,
     ) -> ir::FuncRef;
+    fn debug_tags(&self, _srcloc: ir::SourceLoc) -> Vec<ir::DebugTag> {
+        vec![]
+    }
 
     fn trap(&mut self, builder: &mut FunctionBuilder, trap: ir::TrapCode) {
         match (
@@ -36,12 +39,14 @@ pub trait TranslateTrap {
             // pass in our trap code. Leave a debug `unreachable` in place
             // afterwards as a defense-in-depth measure.
             (false, Some(trap)) => {
+                let debug_tags = self.debug_tags(builder.srcloc());
                 let trap_libcall = self.builtin_funcref(builder, BuiltinFunctionIndex::trap());
                 let vmctx = self.vmctx_val(&mut builder.cursor());
                 let trap_code = builder.ins().iconst(I8, i64::from(trap as u8));
                 builder.ins().call(trap_libcall, &[vmctx, trap_code]);
                 let raise_libcall = self.builtin_funcref(builder, BuiltinFunctionIndex::raise());
-                builder.ins().call(raise_libcall, &[vmctx]);
+                let inst = builder.ins().call(raise_libcall, &[vmctx]);
+                builder.func.debug_tags.set(inst, debug_tags);
                 builder.ins().trap(TRAP_INTERNAL_ASSERT);
             }
         }

tests/all/debug.rs

@@ -694,18 +694,23 @@ async fn hostcall_trap_events() -> wasmtime::Result<()> {
         },
         r#"
     (module
-      (func (export "main")
+      (func (export "main") (result i32)
         i32.const 0
         i32.const 0
         i32.div_u
-        drop))
+        drop
+        i32.const 42))
     "#,
     )?;
 
     debug_event_checker!(
         D, store,
         { 0 ;
-          wasmtime::DebugEvent::Trap(wasmtime_environ::Trap::IntegerDivisionByZero) => {}
+          wasmtime::DebugEvent::Trap(wasmtime_environ::Trap::IntegerDivisionByZero) => {
+              let frame = store.debug_exit_frames().next().unwrap();
+              let (_func, pc) = frame.wasm_function_index_and_pc(&mut store).unwrap().unwrap();
+              assert_eq!(pc, 0x26);
+          }
         }
     );
 
@@ -714,7 +719,7 @@ async fn hostcall_trap_events() -> wasmtime::Result<()> {
 
     let instance = Instance::new_async(&mut store, &module, &[]).await?;
     let func = instance.get_func(&mut store, "main").unwrap();
-    let mut results = [];
+    let mut results = [Val::I32(0)];
     let result = func.call_async(&mut store, &[], &mut results).await;
     assert!(result.is_err()); // Uncaught trap.
     assert_eq!(counter.load(Ordering::Relaxed), 1);

tests/disas/debug-exceptions.wat

@@ -89,6 +89,7 @@
 ;;       bl      #0x3dc
 ;;   ec: ldur    x2, [sp, #0x10]
 ;;       bl      #0x414
+;;       ╰─╼ debug frame state (after previous inst): func key DefinedWasmFunction(StaticModuleIndex(0), DefinedFuncIndex(0)), wasm PC 66, slot at FP-0xc0, locals , stack I32 @ slot+0x8
 ;;   f4: .byte   0x1f, 0xc1, 0x00, 0x00
 ;;       mov     x2, x0
 ;;       mov     w3, w2
@@ -141,6 +142,7 @@
 ;;  19c: bl      #0x3dc
 ;;  1a0: ldur    x2, [sp, #0x10]
 ;;  1a4: bl      #0x414
+;;       ╰─╼ debug frame state (after previous inst): func key DefinedWasmFunction(StaticModuleIndex(0), DefinedFuncIndex(0)), wasm PC 52, slot at FP-0xc0, locals , stack 
 ;;  1a8: .byte   0x1f, 0xc1, 0x00, 0x00
 ;;  1ac: .byte   0x1f, 0xc1, 0x00, 0x00
 ;;  1b0: .byte   0x1f, 0xc1, 0x00, 0x00

tests/disas/debug.wat

@@ -48,6 +48,7 @@
 ;;   67: callq   0x18c
 ;;   6c: movq    %r12, %rdi
 ;;   6f: callq   0x1bd
+;;       ╰─╼ debug frame state (after previous inst): func key DefinedWasmFunction(StaticModuleIndex(0), DefinedFuncIndex(0)), wasm PC 35, slot at FP-0x30, locals I32 @ slot+0x8, I32 @ slot+0xc, stack 
 ;;   74: ud2
 ;;
 ;; wasm[0]::array_to_wasm_trampoline[0]: