Add optimizer pass removing dead code.

hilti/toolchain/src/compiler/optimizer.cc

@@ -24,10 +24,13 @@
 #include <hilti/ast/expressions/logical-or.h>
 #include <hilti/ast/expressions/ternary.h>
 #include <hilti/ast/node.h>
+#include <hilti/ast/operators/function.h>
+#include <hilti/ast/operators/struct.h>
 #include <hilti/ast/operators/tuple.h>
 #include <hilti/ast/scope-lookup.h>
 #include <hilti/ast/statements/block.h>
 #include <hilti/ast/statements/declaration.h>
+#include <hilti/ast/statements/expression.h>
 #include <hilti/ast/type.h>
 #include <hilti/ast/types/bool.h>
 #include <hilti/ast/types/enum.h>
@@ -1622,6 +1625,55 @@ struct DeadStoreVisitor : OptimizerVisitor, visitor::PreOrder<bool, DeadStoreVis
     }
 };
 
+struct DeadCodeVisitor : OptimizerVisitor, visitor::PreOrder<bool, DeadCodeVisitor> {
+    bool prune_uses(Node& node) override {
+        bool any_modification = false;
+
+        while ( true ) {
+            bool modified = false;
+
+            for ( auto i : this->walk(&node) ) {
+                if ( auto x = dispatch(i) )
+                    modified = modified || *x;
+            }
+
+            if ( ! modified )
+                break;
+
+            any_modification = true;
+        }
+
+        return any_modification;
+    }
+
+    result_t operator()(const Module& m, position_t p) {
+        _current_module = &p.node.as<Module>();
+        return false;
+    }
+
+    result_t operator()(const statement::Expression& x, position_t p) {
+        if ( auto ctor = x.expression().tryAs<expression::Ctor>();
+             ctor && (ctor->isConstant() || ! hasChildWithSideEffects(x)) ) {
+            HILTI_DEBUG(logging::debug::Optimizer,
+                        util::fmt("removing side-effect free dead code (%s)", x.meta().location()));
+            removeNode(p);
+            return true;
+        }
+
+        return false;
+    }
+
+    bool hasChildWithSideEffects(const Node& node) const {
+        auto v = visitor::PreOrder<>();
+        auto walk = v.walk(node);
+
+        return std::any_of(walk.begin(), walk.end(), [](auto&& child) {
+            return child.node.template isA<operator_::struct_::MemberCall>() ||
+                   child.node.template isA<operator_::function::Call>();
+        });
+    }
+};
+
 void Optimizer::run() {
     util::timing::Collector _("hilti/compiler/optimizer");
 
@@ -1667,6 +1719,7 @@ void Optimizer::run() {
         {{"constant_folding", []() { return std::make_unique<ConstantFoldingVisitor>(); }},
          {"functions", []() { return std::make_unique<FunctionVisitor>(); }},
          {"members", []() { return std::make_unique<MemberVisitor>(); }},
+         {"dead_code", []() { return std::make_unique<DeadCodeVisitor>(); }},
          {"dead_store", []() { return std::make_unique<DeadStoreVisitor>(); }},
          {"types", []() { return std::make_unique<TypeVisitor>(); }}};
 

tests/Baseline/hilti.optimization.const/log

@@ -7,13 +7,3 @@
 [debug/optimizer] inlining constant 'Foo::t'
 [debug/optimizer] inlining constant 'Foo::t'
 [debug/optimizer] inlining constant 'Foo::t'
-[debug/optimizer] removing declaration for unused function hilti::abort
-[debug/optimizer] removing declaration for unused function hilti::current_time
-[debug/optimizer] removing declaration for unused function hilti::debug
-[debug/optimizer] removing declaration for unused function hilti::debugDedent
-[debug/optimizer] removing declaration for unused function hilti::debugIndent
-[debug/optimizer] removing declaration for unused function hilti::exception_what
-[debug/optimizer] removing declaration for unused function hilti::mktime
-[debug/optimizer] removing declaration for unused function hilti::printValues
-[debug/optimizer] removing declaration for unused function hilti::profiler_start
-[debug/optimizer] removing declaration for unused function hilti::profiler_stop

tests/Baseline/hilti.optimization.dead_code/opt.hlt

@@ -0,0 +1,4 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+module foo {
+
+}

tests/Baseline/hilti.optimization.unimplemented_hook/log

@@ -6,5 +6,7 @@
 [debug/optimizer] removing declaration for unused hook function Foo::global_unimplemented_void
 [debug/optimizer] removing declaration for unused hook function Foo::global_unimplemented_int64
 [debug/optimizer] removing field for unused method Foo::X::unimplemented
+[debug/optimizer] removing side-effect free dead code (<...>/unimplemented_hook.hlt:29:1)
+[debug/optimizer] removing side-effect free dead code (<...>/unimplemented_hook.hlt:35:1)
 [debug/optimizer] removing field for unused method Foo::X::unimplemented_void
 [debug/optimizer] removing field for unused method Foo::X::unimplemented_int64

tests/Baseline/hilti.optimization.unimplemented_hook/opt.hlt

@@ -18,8 +18,6 @@ method hook void X::implemented() {
 }
 
 global_implemented();
-default<void>();
 x.implemented();
-default<void>();
 
 }

tests/Baseline/spicy.optimization.default-parser-functions/log

@@ -202,6 +202,21 @@
 [debug/optimizer] removing field for unused method foo::__register_foo_P2::<anon-struct-9>::parse1
 [debug/optimizer] removing field for unused method foo::__register_foo_P2::<anon-struct-9>::parse2
 [debug/optimizer] removing field for unused method foo::__register_foo_P2::<anon-struct-9>::parse3
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:12:11)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:12:11)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:12:11)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:12:11)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:12:11)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:14:18)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:14:18)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:14:18)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:14:18)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:14:18)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:16:18-21:2)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:16:18-21:2)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:16:18-21:2)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:16:18-21:2)
+[debug/optimizer] removing side-effect free dead code (<...>/default-parser-functions.spicy:17:5)
 [debug/optimizer] removing unused member 'foo::P0::__begin'
 [debug/optimizer] removing unused member 'foo::P0::__filters'
 [debug/optimizer] removing unused member 'foo::P0::__offset'

tests/Baseline/spicy.optimization.default-parser-functions/opt.hlt

@@ -55,7 +55,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     try {
         hilti::debugIndent("spicy");
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         local strong_ref<stream> filtered = Null;
 
@@ -64,15 +63,12 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
 
     }
     catch ( hilti::SystemException __except ) {
-        default<void>();
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         throw;
     }
 
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     return __result;
 }
@@ -81,7 +77,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     # "<...>/default-parser-functions.spicy:14:18"
     local tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::RecoverableFailure>> __result;
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     hilti::debugDedent("spicy");
     __result = (__cur, __lah, __lahe, __error);
@@ -162,7 +157,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     try {
         hilti::debugIndent("spicy");
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         local strong_ref<stream> filtered = Null;
 
@@ -173,13 +167,11 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     catch ( hilti::SystemException __except ) {
         (*self).__on_0x25_error(hilti::exception_what(__except));
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         throw;
     }
 
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     return __result;
 }
@@ -199,7 +191,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     # End parsing production: Variable: x   -> uint<8>
 
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     # "<...>/default-parser-functions.spicy:18:8"
 
@@ -216,7 +207,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     (*self).__on_y((*self).y);
     __error = (*self).__error;
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     hilti::debugDedent("spicy");
     __result = (__cur, __lah, __lahe, __error);

tests/Baseline/spicy.optimization.feature_requirements/log

@@ -422,6 +422,37 @@
 [debug/optimizer] removing field for unused method foo::__register_foo_X6::<anon-struct-21>::parse1
 [debug/optimizer] removing field for unused method foo::__register_foo_X6::<anon-struct-21>::parse2
 [debug/optimizer] removing field for unused method foo::__register_foo_X6::<anon-struct-21>::parse3
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:13:11-15:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:13:11-15:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:13:11-15:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:13:11-15:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:18:11-20:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:18:11-20:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:18:11-20:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:18:11-20:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:23:11)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:23:11)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:23:11)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:23:11)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:23:11)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:26:11-28:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:26:11-28:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:26:11-28:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:26:11-28:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:26:11-28:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:32:11-34:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:32:11-34:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:32:11-34:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:32:11-34:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:32:11-34:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:36:18-40:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:36:18-40:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:36:18-40:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:36:18-40:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:43:11-46:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:43:11-46:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:43:11-46:2)
+[debug/optimizer] removing side-effect free dead code (<...>/feature_requirements.spicy:43:11-46:2)
 [debug/optimizer] removing unused member 'foo::X0::__begin'
 [debug/optimizer] removing unused member 'foo::X0::__filters'
 [debug/optimizer] removing unused member 'foo::X0::__parser'

tests/Baseline/spicy.optimization.feature_requirements/opt.hlt

@@ -128,7 +128,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     try {
         hilti::debugIndent("spicy");
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         local strong_ref<stream> filtered = Null;
 
@@ -137,18 +136,15 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
 
     }
     catch ( hilti::SystemException __except ) {
-        default<void>();
 
             spicy_rt::filter_forward_eod(self);
 
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         throw;
     }
 
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     return __result;
 }
@@ -157,7 +153,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     # "<...>/feature_requirements.spicy:32:11-34:2"
     local tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::RecoverableFailure>> __result;
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
 
         spicy_rt::filter_forward_eod(self);
@@ -265,18 +260,15 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
 
     }
     catch ( hilti::SystemException __except ) {
-        default<void>();
 
             spicy_rt::filter_disconnect(self);
 
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         throw;
     }
 
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     return __result;
 }
@@ -285,7 +277,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     # "<...>/feature_requirements.spicy:36:18-40:2"
     local tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::RecoverableFailure>> __result;
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
 
         spicy_rt::filter_disconnect(self);
@@ -376,16 +367,13 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
 
     }
     catch ( hilti::SystemException __except ) {
-        default<void>();
         (*(*self).data).close();
         (*self).__error = __error;
-        default<void>();
         __error = (*self).__error;
         throw;
     }
 
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     return __result;
 }
@@ -394,7 +382,6 @@ method method tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::Rec
     # "<...>/feature_requirements.spicy:43:11-46:2"
     local tuple<view<stream>, int<64>, iterator<stream>, optional<hilti::RecoverableFailure>> __result;
     (*self).__error = __error;
-    default<void>();
     __error = (*self).__error;
     (*(*self).data).close();
     hilti::debugDedent("spicy");

tests/Baseline/spicy.optimization.unused-functions/log

@@ -315,6 +315,31 @@
 [debug/optimizer] removing field for unused method foo::__register_foo_D::<anon-struct-13>::parse1
 [debug/optimizer] removing field for unused method foo::__register_foo_D::<anon-struct-13>::parse2
 [debug/optimizer] removing field for unused method foo::__register_foo_D::<anon-struct-13>::parse3
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:18:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:18:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:18:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:18:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:18:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:21:17)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:21:17)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:21:17)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:21:17)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:21:17)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:24:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:24:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:24:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:24:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:24:10)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:25:17-27:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:25:17-27:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:25:17-27:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:25:17-27:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:25:17-27:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:30:10-32:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:30:10-32:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:30:10-32:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:30:10-32:2)
+[debug/optimizer] removing side-effect free dead code (<...>/unused-functions.spicy:30:10-32:2)
 [debug/optimizer] removing unused member 'foo::A::__begin'
 [debug/optimizer] removing unused member 'foo::A::__filters'
 [debug/optimizer] removing unused member 'foo::A::__offset'