disable broken emit_isa codegen optimization

JuliaLang · Jul 6, 2018 · 9f71211 · 9f71211
1 parent 4e60aa2
commit 9f71211
Showing 1 changed file with 26 additions and 19 deletions.
diff --git a/src/cgutils.cpp b/src/cgutils.cpp
@@ -1060,26 +1060,33 @@ static void emit_type_error(jl_codectx_t &ctx, const jl_cgval_t &x, Value *type,
 
 static std::pair<Value*, bool> emit_isa(jl_codectx_t &ctx, const jl_cgval_t &x, jl_value_t *type, const std::string *msg)
 {
-    Optional<bool> known_isa;
     jl_value_t *intersected_type = type;
-    if (x.constant)
-        known_isa = jl_isa(x.constant, type);
-    else if (jl_subtype(x.typ, type))
-        known_isa = true;
-    else {
-        intersected_type = jl_type_intersection(x.typ, type);
-        if (intersected_type == (jl_value_t*)jl_bottom_type)
-            known_isa = false;
-    }
-    if (known_isa) {
-        if (!*known_isa && msg) {
-            emit_type_error(ctx, x, literal_pointer_val(ctx, type), *msg);
-            ctx.builder.CreateUnreachable();
-            BasicBlock *failBB = BasicBlock::Create(jl_LLVMContext, "fail", ctx.f);
-            ctx.builder.SetInsertPoint(failBB);
-        }
-        return std::make_pair(ConstantInt::get(T_int1, *known_isa), true);
-    }
+
+    // TODO: This optimization suffers from incorrectness issues due to broken subtyping for
+    // kind types (see https://github.com/JuliaLang/julia/issues/27078). For actual `isa`
+    // calls, this optimization should already have been performed upstream anyway, but
+    // having this optimization in codegen might still be beneficial for `typeassert`s
+    // if we can make it correct.
+    //
+    // Optional<bool> known_isa;
+    // if (x.constant)
+    //     known_isa = jl_isa(x.constant, type);
+    // else if (jl_subtype(x.typ, type))
+    //     known_isa = true;
+    // else {
+    //     intersected_type = jl_type_intersection(x.typ, type);
+    //     if (intersected_type == (jl_value_t*)jl_bottom_type)
+    //         known_isa = false;
+    // }
+    // if (known_isa) {
+    //     if (!*known_isa && msg) {
+    //         emit_type_error(ctx, x, literal_pointer_val(ctx, type), *msg);
+    //         ctx.builder.CreateUnreachable();
+    //         BasicBlock *failBB = BasicBlock::Create(jl_LLVMContext, "fail", ctx.f);
+    //         ctx.builder.SetInsertPoint(failBB);
+    //     }
+    //     return std::make_pair(ConstantInt::get(T_int1, *known_isa), true);
+    // }
 
     // intersection with Type needs to be handled specially
     if (jl_has_intersect_type_not_kind(type)) {