Pop LMF frames in exception handlers on wasm, since the normal pop LMF code might not get executed in case of an exception.

src/mono/mono/metadata/jit-icall-reg.h

@@ -138,6 +138,7 @@ MONO_JIT_ICALL (mini_llvmonly_resolve_iface_call_gsharedvt) \
 MONO_JIT_ICALL (mini_llvmonly_resolve_vcall_gsharedvt) \
 MONO_JIT_ICALL (mini_llvmonly_throw_nullref_exception) \
 MONO_JIT_ICALL (mini_llvmonly_throw_aot_failed_exception) \
+MONO_JIT_ICALL (mini_llvmonly_pop_lmf) \
 MONO_JIT_ICALL (mono_amd64_resume_unwind)	\
 MONO_JIT_ICALL (mono_amd64_start_gsharedvt_call)	\
 MONO_JIT_ICALL (mono_amd64_throw_corlib_exception)	\

src/mono/mono/mini/aot-runtime.h

@@ -11,7 +11,7 @@
 #include "mini.h"
 
 /* Version number of the AOT file format */
-#define MONO_AOT_FILE_VERSION 179
+#define MONO_AOT_FILE_VERSION 180
 
 #define MONO_AOT_TRAMP_PAGE_SIZE 16384
 

src/mono/mono/mini/llvmonly-runtime.c

@@ -815,3 +815,15 @@ mini_llvmonly_throw_aot_failed_exception (const char *name)
 	g_free (msg);
 	mono_llvm_throw_exception ((MonoObject*)ex);
 }
+
+/*
+ * mini_llvmonly_pop_lmf:
+ *
+ *   Pop LMF off the LMF stack.
+ */
+void
+mini_llvmonly_pop_lmf (MonoLMF *lmf)
+{
+	if (lmf->previous_lmf)
+		mono_set_lmf (lmf->previous_lmf);
+}

src/mono/mono/mini/llvmonly-runtime.h

@@ -35,4 +35,6 @@ G_EXTERN_C void mini_llvmonly_throw_nullref_exception (void);
 
 G_EXTERN_C void mini_llvmonly_throw_aot_failed_exception (const char *name);
 
+G_EXTERN_C void mini_llvmonly_pop_lmf (MonoLMF *lmf);
+
 #endif

src/mono/mono/mini/method-to-ir.c

@@ -8052,6 +8052,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 
 #ifdef TARGET_WASM
 			if (common_call && needs_stack_walk)
+				/* If an exception is thrown, the LMF is popped by a call to mini_llvmonly_pop_lmf () */
 				emit_pop_lmf (cfg);
 #endif
 
@@ -11669,6 +11670,17 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 		mono_get_got_var (cfg);
 #endif
 
+#ifdef TARGET_WASM
+	if (cfg->lmf_var) {
+		// mini_llvmonly_pop_lmf () might be called before emit_push_lmf () so initialize the LMF
+		cfg->cbb = init_localsbb;
+		EMIT_NEW_VARLOADA (cfg, ins, cfg->lmf_var, NULL);
+		int lmf_reg = ins->dreg;
+
+		EMIT_NEW_STORE_MEMBASE (cfg, ins, OP_STORE_MEMBASE_IMM, lmf_reg, MONO_STRUCT_OFFSET (MonoLMF, previous_lmf), 0);
+	}
+#endif
+
 	if (cfg->method == method && cfg->got_var)
 		mono_emit_load_got_addr (cfg);
 

src/mono/mono/mini/mini-llvm.c

@@ -4700,6 +4700,24 @@ emit_llvmonly_handler_start (EmitContext *ctx, MonoBasicBlock *bb, LLVMBasicBloc
 		mono_llvm_emit_clear_exception_call (ctx, ctx->builder);
 	}
 
+#ifdef TARGET_WASM
+	if (ctx->cfg->lmf_var) {
+		LLVMValueRef callee;
+		LLVMValueRef args [1];
+		LLVMTypeRef sig = LLVMFunctionType1 (LLVMVoidType (), ctx->module->ptr_type, FALSE);
+
+		/*
+		 * There might be an LMF on the stack inserted to enable stack walking, see
+		 * method_needs_stack_walk (). If an exception is thrown, the LMF popping code
+		 * is not executed, so do it here.
+		 */
+		g_assert (ctx->addresses [ctx->cfg->lmf_var->dreg]);
+		callee = get_callee (ctx, sig, MONO_PATCH_INFO_JIT_ICALL_ADDR, GUINT_TO_POINTER (MONO_JIT_ICALL_mini_llvmonly_pop_lmf));
+		args [0] = convert (ctx, ctx->addresses [ctx->cfg->lmf_var->dreg], ctx->module->ptr_type);
+		emit_call (ctx, bb, &ctx->builder, callee, args, 1);
+	}
+#endif
+
 	LLVMBuilderRef handler_builder = create_builder (ctx);
 	LLVMBasicBlockRef target_bb = ctx->bblocks [bb->block_num].call_handler_target_bb;
 	LLVMPositionBuilderAtEnd (handler_builder, target_bb);

src/mono/mono/mini/mini-runtime.c

@@ -4913,6 +4913,7 @@ register_icalls (void)
 	register_icall (mini_llvmonly_init_delegate_virtual, mono_icall_sig_void_object_object_ptr, TRUE);
 	register_icall (mini_llvmonly_throw_nullref_exception, mono_icall_sig_void, TRUE);
 	register_icall (mini_llvmonly_throw_aot_failed_exception, mono_icall_sig_void_ptr, TRUE);
+	register_icall (mini_llvmonly_pop_lmf, mono_icall_sig_void_ptr, TRUE);
 
 	register_icall (mono_get_assembly_object, mono_icall_sig_object_ptr, TRUE);
 	register_icall (mono_get_method_object, mono_icall_sig_object_ptr, TRUE);