From b08bd7db2827b882fdbb99f1bed6dbd4dfae0707 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Mon, 20 Jul 2020 19:22:14 -0400
Subject: [PATCH] gf lookup: avoid creating unintended specializations and
 cache misses (#36704)

The typemap code was forgetting to handle the case where the user needed
to look for something complicated (like AbstractVec{Float64}) in the
method table cache (such as for ==).
---
 base/compiler/typelattice.jl |  4 +++-
 base/show.jl                 |  4 ++--
 src/typemap.c                | 17 +++++++++++++++--
 test/subarray.jl             |  2 +-
 4 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/base/compiler/typelattice.jl b/base/compiler/typelattice.jl
index 2ea65bb749bf0..69c0214570c83 100644
--- a/base/compiler/typelattice.jl
+++ b/base/compiler/typelattice.jl
@@ -84,8 +84,10 @@ struct NotFound end
 
 const NOT_FOUND = NotFound()
 
-const CompilerTypes = Union{Type, MaybeUndef, Const, Conditional, NotFound, PartialStruct}
+const CompilerTypes = Union{MaybeUndef, Const, Conditional, NotFound, PartialStruct}
 ==(x::CompilerTypes, y::CompilerTypes) = x === y
+==(x::Type, y::CompilerTypes) = false
+==(x::CompilerTypes, y::Type) = false
 
 #################
 # lattice logic #
diff --git a/base/show.jl b/base/show.jl
index 7597e5f52fc8a..03392d56653a0 100644
--- a/base/show.jl
+++ b/base/show.jl
@@ -2492,11 +2492,11 @@ type, indicating that any recursed calls are not at the top level.
 Printing the parent as `::Array{Float64,3}` is the fallback (non-toplevel)
 behavior, because no specialized method for `Array` has been defined.
 """
-function showarg(io::IO, ::Type{T}, toplevel) where {T}
+function showarg(io::IO, T::Type, toplevel)
     toplevel || print(io, "::")
     print(io, "Type{", T, "}")
 end
-function showarg(io::IO, x, toplevel)
+function showarg(io::IO, @nospecialize(x), toplevel)
     toplevel || print(io, "::")
     print(io, typeof(x))
 end
diff --git a/src/typemap.c b/src/typemap.c
index 2f308c8878605..68df2d1a30004 100644
--- a/src/typemap.c
+++ b/src/typemap.c
@@ -967,14 +967,15 @@ jl_typemap_entry_t *jl_typemap_level_assoc_exact(jl_typemap_level_t *cache, jl_v
             jl_typemap_entry_t *ml = jl_typemap_assoc_exact(ml_or_cache, arg1, args, n, offs+1, world);
             if (ml) return ml;
         }
-        if (jl_is_kind(ty) && cache->tname != (jl_array_t*)jl_an_empty_vec_any) {
+        jl_array_t *tname = cache->tname;
+        if (jl_is_kind(ty) && tname != (jl_array_t*)jl_an_empty_vec_any) {
             jl_value_t *name = jl_type_extract_name(a1);
             if (name) {
                 if (ty != (jl_value_t*)jl_datatype_type)
                     a1 = jl_unwrap_unionall(((jl_typename_t*)name)->wrapper);
                 while (1) {
                     jl_typemap_t *ml_or_cache = mtcache_hash_lookup(
-                            cache->tname, (jl_value_t*)((jl_datatype_t*)a1)->name);
+                            tname, (jl_value_t*)((jl_datatype_t*)a1)->name);
                     jl_typemap_entry_t *ml = jl_typemap_assoc_exact(ml_or_cache, arg1, args, n, offs+1, world);
                     if (ml) return ml;
                     if (a1 == (jl_value_t*)jl_any_type)
@@ -982,6 +983,18 @@ jl_typemap_entry_t *jl_typemap_level_assoc_exact(jl_typemap_level_t *cache, jl_v
                     a1 = (jl_value_t*)((jl_datatype_t*)a1)->super;
                 }
             }
+            else {
+                // couldn't figure out unique `name` initial point, so must scan all for matches
+                size_t i, l = jl_array_len(tname);
+                jl_typemap_t **data = (jl_typemap_t **)jl_array_ptr_data(tname);
+                for (i = 1; i < l; i += 2) {
+                    jl_typemap_t *ml_or_cache = data[i];
+                    if (ml_or_cache == NULL || ml_or_cache == jl_nothing)
+                        continue;
+                    jl_typemap_entry_t *ml = jl_typemap_assoc_exact(ml_or_cache, arg1, args, n, offs + 1, world);
+                    if (ml) return ml;
+                }
+            }
         }
         if (cache->name1 != (jl_array_t*)jl_an_empty_vec_any) {
             while (1) {
diff --git a/test/subarray.jl b/test/subarray.jl
index fa4101852cd28..cf03d1b53ca64 100644
--- a/test/subarray.jl
+++ b/test/subarray.jl
@@ -36,7 +36,7 @@ _Agen(A, i1, i2, i3, i4, i5, i6) = [A[j1,j2,j3,j4,j5,j6] for j1 in i1, j2 in i2,
 
 function replace_colon(A::AbstractArray, I)
     Iout = Vector{Any}(undef, length(I))
-    I == (:,) && return (1:length(A),)
+    I === (:,) && return (1:length(A),)
     for d = 1:length(I)
         Iout[d] = isa(I[d], Colon) ? (1:size(A,d)) : I[d]
     end