C#: Fix bad join-order in dispatch library

hvitved · hvitved · commit f5471e34f877 · 2021-12-22T10:45:51.000+01:00
Before
```
[2021-12-22 09:46:31] (395s) Tuple counts for Dispatch::Internal::hasCallable#fff/3@258418l2 after 5m27s:
                      49000       ~0%      {2} r1 = JOIN Declaration::Declaration::getUnboundDeclaration_dispred#ff_10#join_rhs WITH project#Dispatch::Internal::DispatchMethodOrAccessorCall::getAStaticTargetExt#ff ON FIRST 1 OUTPUT Lhs.1 'c', Rhs.0

                      31302       ~3%      {3} r2 = JOIN r1 WITH Type::ValueOrRefType::getAMember_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.0 'c', Lhs.1 'source', Rhs.1

                      299700      ~0%      {3} r3 = JOIN r1 WITH Type::ValueOrRefType::hasOverriddenMember_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.0 'c', Lhs.1 'source', Rhs.1

                      16650       ~1%      {3} r4 = JOIN r1 WITH Property::Accessor::getDeclaration_dispred#ff ON FIRST 1 OUTPUT Rhs.1, Lhs.1 'source', Lhs.0 'c'

                      15984       ~0%      {3} r5 = JOIN r4 WITH Type::ValueOrRefType::getAMember_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.2 'c', Lhs.1 'source', Rhs.1

                      315684      ~1%      {3} r6 = r3 UNION r5
                      346986      ~1%      {3} r7 = r2 UNION r6

                      0           ~0%      {3} r8 = JOIN r4 WITH Type::ValueOrRefType::hasOverriddenMember_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.2 'c', Lhs.1 'source', Rhs.1

                      666         ~0%      {3} r9 = JOIN r1 WITH Type::hasNonOverriddenMember#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1 'source', Lhs.0 'c'
                      0           ~0%      {3} r10 = JOIN r9 WITH boundedFastTC(Type::ValueOrRefType::getBaseClass_dispred#ff_10#join_rhs,Dispatch::Internal::hasCallable#fff#higher_order_body) ON FIRST 1 OUTPUT Lhs.2 'c', Lhs.1 'source', Rhs.1

                      0           ~0%      {3} r11 = JOIN r4 WITH Type::hasNonOverriddenMember#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1 'source', Lhs.2 'c'
                      0           ~0%      {3} r12 = JOIN r11 WITH boundedFastTC(Type::ValueOrRefType::getBaseClass_dispred#ff_10#join_rhs,Dispatch::Internal::hasCallable#fff#higher_order_body#1) ON FIRST 1 OUTPUT Lhs.2 'c', Lhs.1 'source', Rhs.1

                      0           ~0%      {3} r13 = r10 UNION r12
                      0           ~0%      {3} r14 = r8 UNION r13
                      346986      ~1%      {3} r15 = r7 UNION r14
                      11963234000 ~2%      {4} r16 = JOIN r15 WITH Dispatch::Internal::hasOverrider#ff ON FIRST 1 OUTPUT Lhs.2, Rhs.1 't', Lhs.1 'source', Lhs.0 'c'
                      207126      ~27%     {3} r17 = JOIN r16 WITH Unification::Gvn::Cached::getGlobalValueNumber#ff ON FIRST 2 OUTPUT Lhs.2 'source', Lhs.1 't', Lhs.3 'c'
                                           return r17
```

After
```
[2021-12-22 10:39:41] (0s) Tuple counts for Dispatch::Internal::hasCallable0#fff/3@82341e2h after 331ms:
                      93569  ~0%      {2} r1 = JOIN Type::ValueOrRefType::getAMember_dispred#fb_10#join_rhs WITH OverridableCallable::OverridableCallable#f ON FIRST 1 OUTPUT Rhs.0 'c', Lhs.1

                      511767 ~0%      {2} r2 = JOIN Type::ValueOrRefType::hasOverriddenMember_dispred#ff_10#join_rhs WITH OverridableCallable::OverridableCallable#f ON FIRST 1 OUTPUT Rhs.0 'c', Lhs.1

                      35659  ~0%      {2} r3 = JOIN OverridableCallable::OverridableCallable#f WITH Property::Accessor::getDeclaration_dispred#ff ON FIRST 1 OUTPUT Rhs.1, Lhs.0 'c'

                      35659  ~4%      {2} r4 = JOIN r3 WITH Type::ValueOrRefType::getAMember_dispred#fb_10#join_rhs ON FIRST 1 OUTPUT Lhs.1 'c', Rhs.1

                      547426 ~0%      {2} r5 = r2 UNION r4
                      640995 ~4%      {2} r6 = r1 UNION r5

                      74835  ~4%      {2} r7 = JOIN r3 WITH Type::ValueOrRefType::hasOverriddenMember_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.1 'c', Rhs.1

                      32748  ~0%      {2} r8 = JOIN Type::hasNonOverriddenMember#fb_10#join_rhs WITH OverridableCallable::OverridableCallable#f ON FIRST 1 OUTPUT Lhs.1, Rhs.0 'c'
                      171228 ~0%      {2} r9 = JOIN r8 WITH boundedFastTC(Type::ValueOrRefType::getBaseClass_dispred#ff_10#join_rhs,Dispatch::Internal::hasCallable0#fff#higher_order_body) ON FIRST 1 OUTPUT Lhs.1 'c', Rhs.1

                      9056   ~0%      {2} r10 = JOIN r3 WITH Type::hasNonOverriddenMember#fb_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1 'c'
                      23633  ~1%      {2} r11 = JOIN r10 WITH boundedFastTC(Type::ValueOrRefType::getBaseClass_dispred#ff_10#join_rhs,Dispatch::Internal::hasCallable0#fff#higher_order_body#1) ON FIRST 1 OUTPUT Lhs.1 'c', Rhs.1

                      194861 ~0%      {2} r12 = r9 UNION r11
                      269696 ~0%      {2} r13 = r7 UNION r12
                      910691 ~4%      {2} r14 = r6 UNION r13
                      910691 ~2%      {3} r15 = JOIN r14 WITH Declaration::Declaration::getUnboundDeclaration_dispred#ff ON FIRST 1 OUTPUT Rhs.1 'source', Lhs.0 'c', Lhs.1
                      579872 ~2%      {3} r16 = JOIN r15 WITH project#Dispatch::Internal::DispatchMethodOrAccessorCall::getAStaticTargetExt#ff ON FIRST 1 OUTPUT Lhs.2, Lhs.1 'c', Lhs.0 'source'
                      753465 ~41%     {3} r17 = JOIN r16 WITH Unification::Gvn::Cached::getGlobalValueNumber#ff ON FIRST 1 OUTPUT Rhs.1 't', Lhs.1 'c', Lhs.2 'source'
                                      return r17

[2021-12-22 10:39:41] (0s) Tuple counts for Dispatch::Internal::hasCallable#fff/3@e44e67tv after 24ms:
                      201843 ~0%     {3} r1 = JOIN Dispatch::Internal::hasOverrider#ff WITH Dispatch::Internal::hasCallable0#fff ON FIRST 2 OUTPUT Lhs.0 't', Lhs.1 'c', Rhs.2 'source'
                                     return r1
```
diff --git a/csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll b/csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll
@@ -233,18 +233,23 @@ private module Internal {
   }
 
   pragma[noinline]
-  private predicate hasOverrider(OverridableCallable oc, Gvn::GvnType t) {
+  private predicate hasOverrider(Gvn::GvnType t, OverridableCallable oc) {
     exists(oc.getAnOverrider(any(ValueOrRefType t0 | Gvn::getGlobalValueNumber(t0) = t)))
   }
 
   pragma[noinline]
-  private predicate hasCallable(OverridableCallable source, Gvn::GvnType t, OverridableCallable c) {
+  private predicate hasCallable0(Gvn::GvnType t, OverridableCallable c, OverridableCallable source) {
     c.getUnboundDeclaration() = source and
     any(ValueOrRefType t0 | Gvn::getGlobalValueNumber(t0) = t).hasCallable(c) and
-    hasOverrider(c, t) and
     source = any(DispatchMethodOrAccessorCall call).getAStaticTargetExt()
   }
 
+  pragma[noinline]
+  private predicate hasCallable(Gvn::GvnType t, OverridableCallable c, OverridableCallable source) {
+    hasCallable0(t, c, source) and
+    hasOverrider(t, c)
+  }
+
   abstract private class DispatchMethodOrAccessorCall extends DispatchCallImpl {
     pragma[noinline]
     OverridableCallable getAStaticTargetExt() {
@@ -260,7 +265,7 @@ private module Internal {
 
     pragma[noinline]
     private predicate hasSubsumedQualifierType(Gvn::GvnType t) {
-      hasOverrider(_, t) and
+      hasOverrider(t, _) and
       exists(Type t0 |
         t0 = getAPossibleType(this.getQualifier(), false) and
         not t0 instanceof TypeParameter
@@ -287,7 +292,7 @@ private module Internal {
     pragma[nomagic]
     predicate hasSubsumedQualifierTypeOverridden(Gvn::GvnType t, OverridableCallable c) {
       this.hasSubsumedQualifierType(t) and
-      hasCallable(any(OverridableCallable oc | oc = this.getAStaticTargetExt()), t, c)
+      hasCallable(t, c, any(OverridableCallable oc | oc = this.getAStaticTargetExt()))
     }
 
     /**
@@ -553,7 +558,7 @@ private module Internal {
 
     pragma[nomagic]
     private predicate contextArgHasSubsumedType(DispatchCall ctx, Gvn::GvnType t) {
-      hasOverrider(_, t) and
+      hasOverrider(t, _) and
       exists(Gvn::GvnType t0 | this.contextArgHasNonTypeParameterType(ctx, t0) |
         t = t0
         or
