Optimize the mangling of specialized generic functions. (#2845)

Don't include all the dependent types, which are not really needed to get unique symbol names.
This reduces the symbol length (and therefore the binary size) significantly.

Thanks, rjmccall, for your help!

Author: eeckstein

lib/SIL/Mangle.cpp

@@ -56,10 +56,21 @@ static void mangleSubstitution(Mangler &M, Substitution Sub) {
 void GenericSpecializationMangler::mangleSpecialization() {
   Mangler &M = getMangler();
 
-  for (auto &Sub : Subs) {
-    mangleSubstitution(M, Sub);
-    M.append('_');
+  SILFunctionType *FTy = Function->getLoweredFunctionType();
+  CanGenericSignature Sig = FTy->getGenericSignature();
+
+  unsigned idx = 0;
+  for (Type DepType : Sig->getAllDependentTypes()) {
+    // It is sufficient to only mangle the substitutions of the "primary"
+    // dependent types. As all other dependent types are just derived from the
+    // primary types, this will give us unique symbol names.
+    if (DepType->is<GenericTypeParamType>()) {
+      mangleSubstitution(M, Subs[idx]);
+      M.append('_');
+    }
+    ++idx;
   }
+  assert(idx == Subs.size() && "subs not parallel to dependent types");
 }
 
 //===----------------------------------------------------------------------===//

test/SILOptimizer/eager_specialize.sil

@@ -96,7 +96,7 @@ bb0(%0 : $*T, %1 : $G<T>, %2 : $*T.Elt):
 
 // Specialization getGenericContainer<S, X>
 //
-// CHECK-LABEL: sil shared @_TTSg5V4main1SS0_S_6HasEltS__VS_1XS2_S_5AnEltS____TF16eager_specialize19getGenericContaineruRxS_6HasEltwx3EltS_5AnEltrFTGVS_1Gx_1ewxS1__x : $@convention(thin) (G<S>, X) -> S {
+// CHECK-LABEL: sil shared @_TTSg5V4main1SS0_S_6HasEltS____TF16eager_specialize19getGenericContaineruRxS_6HasEltwx3EltS_5AnEltrFTGVS_1Gx_1ewxS1__x : $@convention(thin) (G<S>, X) -> S {
 // CHECK: bb0(%0 : $G<S>, %1 : $X):
 // CHECK:   return %{{.*}} : $S
 
@@ -126,7 +126,7 @@ bb0(%0 : $*T, %1 : $G<T>, %2 : $*T.Elt):
 // CHECK:   %16 = unchecked_addr_cast %2 : $*T.Elt to $*X
 // CHECK:   %17 = load %16 : $*X
   // function_ref specialized getGenericContainer<A where ...> (G<A>, e : A.Elt) -> A
-// CHECK:   %18 = function_ref @_TTSg5V4main1SS0_S_6HasEltS__VS_1XS2_S_5AnEltS____TF16eager_specialize19getGenericContaineruRxS_6HasEltwx3EltS_5AnEltrFTGVS_1Gx_1ewxS1__x : $@convention(thin) (G<S>, X) -> S
+// CHECK:   %18 = function_ref @_TTSg5V4main1SS0_S_6HasEltS____TF16eager_specialize19getGenericContaineruRxS_6HasEltwx3EltS_5AnEltrFTGVS_1Gx_1ewxS1__x : $@convention(thin) (G<S>, X) -> S
 // CHECK:   %19 = apply %18(%15, %17) : $@convention(thin) (G<S>, X) -> S
 // CHECK:   store %19 to %14 : $*S
 // CHECK:   %21 = tuple ()
@@ -196,7 +196,7 @@ bb2:                                              // Preds: bb0
 }
 
 // specialized divideNum<A where ...> (A, den : A) throws -> A
-// CHECK-LABEL: sil shared @_TTSg5SiSis13SignedIntegers_SiSis33_BuiltinIntegerLiteralConvertibles_SiSis12SignedNumbers_SiSiS0_s_Si___TF16eager_specialize9divideNumuRxs13SignedIntegerrFzTx3denx_x : $@convention(thin) (Int, Int) -> (Int, @error ErrorProtocol) {
+// CHECK-LABEL: sil shared @_TTSg5SiSis13SignedIntegers___TF16eager_specialize9divideNumuRxs13SignedIntegerrFzTx3denx_x : $@convention(thin) (Int, Int) -> (Int, @error ErrorProtocol) {
 // CHECK: bb0(%0 : $Int, %1 : $Int):
 // CHECK: return %{{.*}}
 // CHECK: throw %{{.*}}
@@ -238,7 +238,7 @@ bb2:                                              // Preds: bb0
 // CHECK:   %{{.*}} = unchecked_addr_cast %2 : $*T to $*Int
 // CHECK:   %{{.*}} = load %{{.*}} : $*Int
 // CHECK:   // function_ref specialized divideNum<A where ...> (A, den : A) throws -> A
-// CHECK:   %{{.*}} = function_ref @_TTSg5SiSis13SignedIntegers_SiSis33_BuiltinIntegerLiteralConvertibles_SiSis12SignedNumbers_SiSiS0_s_Si___TF16eager_specialize9divideNumuRxs13SignedIntegerrFzTx3denx_x : $@convention(thin) (Int, Int) -> (Int, @error ErrorProtocol)
+// CHECK:   %{{.*}} = function_ref @_TTSg5SiSis13SignedIntegers___TF16eager_specialize9divideNumuRxs13SignedIntegerrFzTx3denx_x : $@convention(thin) (Int, Int) -> (Int, @error ErrorProtocol)
 // CHECK:   try_apply %{{.*}}(%{{.*}}, %{{.*}}) : $@convention(thin) (Int, Int) -> (Int, @error ErrorProtocol), normal bb8, error bb7
 
 // CHECK: bb7(%{{.*}} : $ErrorProtocol):                        // Preds: bb6

test/SILOptimizer/prespecialize.swift

@@ -8,10 +8,10 @@
 // CHECK-LABEL: sil [noinline] @_TF13prespecialize4testFTRGSaSi_4sizeSi_T_ 
 //
 // function_ref specialized Collection<A where ...>.makeIterator() -> IndexingIterator<A>
-// CHECK: function_ref @_TTSgq5GVs14CountableRangeSi_GS_Si_s10Collections_SiSis10Comparables_SiSis13SignedIntegers_SiSis33_BuiltinIntegerLiteralConvertibles_SiSis12SignedNumbers_SiSiS3_s_Si_GS_Si_GS_Si_s13IndexableBasesGS_Si_s8Sequences_SiSiS1_s_GVs16IndexingIteratorGS_Si__GS7_GS_Si__s16IteratorProtocols_Si_GS_Si__Si_GS_Si_GS_Si_S5_sGS_Si_S6_s_SiSiS1_s_GS7_GS_Si__GS7_GS_Si__S8_s_Si_GS_Si__Si_Si___TFesRxs10Collectionwx8IteratorzGVs16IndexingIteratorx_wx8_ElementzWxS0_7Element_rS_12makeIteratorfT_GS1_x_
+// CHECK: function_ref @_TTSgq5GVs14CountableRangeSi_GS_Si_s10Collections___TFesRxs10Collectionwx8IteratorzGVs16IndexingIteratorx_wx8_ElementzWxS0_7Element_rS_12makeIteratorfT_GS1_x_
 //
 // function_ref specialized IndexingIterator.next() -> A._Element?
-// CHECK: function_ref @_TTSgq5GVs14CountableRangeSi_GS_Si_s13IndexableBases_SiSis10Comparables_GS_Si__Si___TFVs16IndexingIterator4nextfT_GSqwx8_Element_
+// CHECK: function_ref @_TTSgq5GVs14CountableRangeSi_GS_Si_s13IndexableBases___TFVs16IndexingIterator4nextfT_GSqwx8_Element_
 //
 // Look for generic specialization <Swift.Int> of Swift.Array.subscript.getter : (Swift.Int) -> A
 // CHECK: function_ref {{@_TTSgq5Si___TFSag9subscriptFSix|@_TTSg5Si___TFSaap9subscriptFSix}}

test/SILOptimizer/specialize_reabstraction.sil

@@ -66,7 +66,7 @@ sil @test : $@convention(thin) (Val<Bool>, Val<Int>) -> Val<(Bool, Int)> {
 bb0(%0 : $Val<Bool>, %1 : $Val<Int>):
   // CHECK: [[COERCE:%.*]] = function_ref @coerce
   %2 = function_ref @coerce : $@convention(thin) <τ_0_0, τ_0_1, τ_0_2> (@owned @callee_owned (@owned Ref<τ_0_0>) -> @owned @callee_owned (@owned Ref<τ_0_1>) -> @owned Ref<τ_0_2>) -> @owned @callee_owned (Val<τ_0_1>) -> Val<τ_0_2>
-  // CHECK: [[MERGE:%.*]] = function_ref @_TTSg5GC4main3RefSb_GS0_Sb_S_8RefProtoS__Sb_Si__merge_curried
+  // CHECK: [[MERGE:%.*]] = function_ref @_TTSg5GC4main3RefSb_GS0_Sb_S_8RefProtoS__Si__merge_curried
   %3 = function_ref @merge_curried : $@convention(thin) <τ_0_0 where τ_0_0 : RefProto><τ_1_0> (@in τ_0_0) -> @owned @callee_owned (@owned Ref<τ_1_0>) -> @owned Ref<(τ_0_0.T, τ_1_0)>
   // CHECK: [[PARTIAL:%.*]] = partial_apply [[MERGE]]()
   %4 = partial_apply %3<Ref<Bool>, Bool, Int>() : $@convention(thin) <τ_0_0 where τ_0_0 : RefProto><τ_1_0> (@in τ_0_0) -> @owned @callee_owned (@owned Ref<τ_1_0>) -> @owned Ref<(τ_0_0.T, τ_1_0)>