reduce max Union length in tmerge (#30833)

JuliaLang · Jan 31, 2019 · a811eac · a811eac
1 parent 2bae4ae
commit a811eac
Show file tree

Hide file tree

Showing 3 changed files with 10 additions and 8 deletions.
diff --git a/base/compiler/typelimits.jl b/base/compiler/typelimits.jl
@@ -5,6 +5,7 @@
 #########################
 
 const MAX_TYPEUNION_COMPLEXITY = 3
+const MAX_TYPEUNION_LENGTH = 3
 const MAX_INLINE_CONST_SIZE = 256
 
 #########################
@@ -373,7 +374,7 @@ function tmerge(@nospecialize(typea), @nospecialize(typeb))
         end
     end
     u = Union{types...}
-    if unioncomplexity(u) <= MAX_TYPEUNION_COMPLEXITY
+    if unionlen(u) <= MAX_TYPEUNION_LENGTH && unioncomplexity(u) <= MAX_TYPEUNION_COMPLEXITY
         # don't let type unions get too big, if the above didn't reduce it enough
         return u
     end
@@ -400,7 +401,7 @@ function tuplemerge(a::DataType, b::DataType)
     p = Vector{Any}(undef, lt + vt)
     for i = 1:lt
         ui = Union{ap[i], bp[i]}
-        if unioncomplexity(ui) < MAX_TYPEUNION_COMPLEXITY
+        if unionlen(ui) <= MAX_TYPEUNION_LENGTH && unioncomplexity(ui) <= MAX_TYPEUNION_COMPLEXITY
             p[i] = ui
         else
             p[i] = Any

diff --git a/base/compiler/typeutils.jl b/base/compiler/typeutils.jl
@@ -146,10 +146,13 @@ end
 
 # unioncomplexity estimates the number of calls to `tmerge` to obtain the given type by
 # counting the Union instances, taking also into account those hidden in a Tuple or UnionAll
-unioncomplexity(u::Union) = 1 + unioncomplexity(u.a) + unioncomplexity(u.b)
+function unioncomplexity(u::Union)
+    inner = max(unioncomplexity(u.a), unioncomplexity(u.b))
+    return inner == 0 ? 0 : 1 + inner
+end
 function unioncomplexity(t::DataType)
     t.name === Tuple.name || return 0
-    c = 0
+    c = 1
     for ti in t.parameters
         ci = unioncomplexity(ti)
         if ci > c

diff --git a/test/compiler/inference.jl b/test/compiler/inference.jl
@@ -71,10 +71,8 @@ tmerge_test(Tuple{}, Tuple{Complex, Vararg{Union{ComplexF32, ComplexF64}}},
     Tuple{Vararg{Complex}})
 @test Core.Compiler.tmerge(Tuple{}, Union{Int16, Nothing, Tuple{ComplexF32, ComplexF32}}) ==
     Union{Int16, Nothing, Tuple{Vararg{ComplexF32}}}
-@test Core.Compiler.tmerge(Int32, Union{Int16, Nothing, Tuple{ComplexF32, ComplexF32}}) ==
-    Union{Int16, Int32, Nothing, Tuple{ComplexF32, ComplexF32}}
-@test Core.Compiler.tmerge(Union{Int32, Nothing, Tuple{ComplexF32}}, Union{Int16, Nothing, Tuple{ComplexF32, ComplexF32}}) ==
-    Union{Int16, Int32, Nothing, Tuple{Vararg{ComplexF32}}}
+@test Core.Compiler.tmerge(Union{Int32, Nothing, Tuple{ComplexF32}}, Union{Int32, Nothing, Tuple{ComplexF32, ComplexF32}}) ==
+    Union{Int32, Nothing, Tuple{Vararg{ComplexF32}}}
 
 # issue 9770
 @noinline x9770() = false