From 29ab6d22177bca597e5fe1cc582f880b1e0f882d Mon Sep 17 00:00:00 2001
From: Shuhei Kadowaki <aviatesk@gmail.com>
Date: Wed, 2 Aug 2023 14:53:44 -0400
Subject: [PATCH] effects: fix `:nothrow` modeling of `getglobal`

---
 base/compiler/tfuncs.jl  | 21 ++++++++++-----------
 test/compiler/effects.jl | 12 ++++++++++++
 2 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/base/compiler/tfuncs.jl b/base/compiler/tfuncs.jl
index e431de009affc..0df0ac036ccd5 100644
--- a/base/compiler/tfuncs.jl
+++ b/base/compiler/tfuncs.jl
@@ -2343,19 +2343,18 @@ function getfield_effects(𝕃::AbstractLattice, arginfo::ArgInfo, @nospecialize
 end
 
 function getglobal_effects(argtypes::Vector{Any}, @nospecialize(rt))
+    2 ≤ length(argtypes) ≤ 3 || return EFFECTS_THROWS
     consistent = inaccessiblememonly = ALWAYS_FALSE
     nothrow = false
-    if length(argtypes) ≥ 2
-        M, s = argtypes[1], argtypes[2]
-        if getglobal_nothrow(M, s)
-            nothrow = true
-            # typeasserts below are already checked in `getglobal_nothrow`
-            Mval, sval = (M::Const).val::Module, (s::Const).val::Symbol
-            if isconst(Mval, sval)
-                consistent = ALWAYS_TRUE
-                if is_mutation_free_argtype(rt)
-                    inaccessiblememonly = ALWAYS_TRUE
-                end
+    M, s = argtypes[1], argtypes[2]
+    if (length(argtypes) == 3 ? getglobal_nothrow(M, s, argtypes[3]) : getglobal_nothrow(M, s))
+        nothrow = true
+        # typeasserts below are already checked in `getglobal_nothrow`
+        Mval, sval = (M::Const).val::Module, (s::Const).val::Symbol
+        if isconst(Mval, sval)
+            consistent = ALWAYS_TRUE
+            if is_mutation_free_argtype(rt)
+                inaccessiblememonly = ALWAYS_TRUE
             end
         end
     end
diff --git a/test/compiler/effects.jl b/test/compiler/effects.jl
index c72fb9e1deb05..3e2df80c8d9d1 100644
--- a/test/compiler/effects.jl
+++ b/test/compiler/effects.jl
@@ -1011,3 +1011,15 @@ end
     isinf(y) && return zero(y)
     irinterp_nothrow_override(true, y)
 end |> Core.Compiler.is_nothrow
+
+# getglobal effects
+const my_defined_var = 42
+@test Base.infer_effects() do
+    getglobal(@__MODULE__, :my_defined_var, :monotonic)
+end |> Core.Compiler.is_foldable_nothrow
+@test Base.infer_effects() do
+    getglobal(@__MODULE__, :my_defined_var, :foo)
+end |> !Core.Compiler.is_nothrow
+@test Base.infer_effects() do
+    getglobal(@__MODULE__, :my_defined_var, :foo, nothing)
+end |> !Core.Compiler.is_nothrow