optimizer: do not delete statements that may not :terminate

Author: aviatesk

base/compiler/optimize.jl

@@ -48,9 +48,9 @@ const IR_FLAG_INACCESSIBLEMEM_OR_ARGMEM = one(UInt32) << 11
 const NUM_IR_FLAGS = 12 # sync with julia.h
 
 const IR_FLAGS_EFFECTS =
-    IR_FLAG_CONSISTENT | IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW | IR_FLAG_NOUB
+    IR_FLAG_CONSISTENT | IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW | IR_FLAG_TERMINATES | IR_FLAG_NOUB
 
-const IR_FLAGS_REMOVABLE = IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW
+const IR_FLAGS_REMOVABLE = IR_FLAG_EFFECT_FREE | IR_FLAG_NOTHROW | IR_FLAG_TERMINATES
 
 const IR_FLAGS_NEEDS_EA = IR_FLAG_EFIIMO | IR_FLAG_INACCESSIBLEMEM_OR_ARGMEM
 
@@ -69,6 +69,9 @@ function flags_for_effects(effects::Effects)
     if is_nothrow(effects)
         flags |= IR_FLAG_NOTHROW
     end
+    if is_terminates(effects)
+        flags |= IR_FLAG_TERMINATES
+    end
     if is_inaccessiblemem_or_argmemonly(effects)
         flags |= IR_FLAG_INACCESSIBLEMEM_OR_ARGMEM
     end
@@ -338,7 +341,8 @@ function stmt_effect_flags(𝕃ₒ::AbstractLattice, @nospecialize(stmt), @nospe
             consistent = is_consistent(effects)
             effect_free = is_effect_free(effects)
             nothrow = is_nothrow(effects)
-            removable = effect_free & nothrow
+            terminates = is_terminates(effects)
+            removable = effect_free & nothrow & terminates
             return (consistent, removable, nothrow)
         elseif head === :new
             return new_expr_effect_flags(𝕃ₒ, args, src)
@@ -349,7 +353,8 @@ function stmt_effect_flags(𝕃ₒ::AbstractLattice, @nospecialize(stmt), @nospe
             consistent = is_consistent(effects)
             effect_free = is_effect_free(effects)
             nothrow = is_nothrow(effects)
-            removable = effect_free & nothrow
+            terminates = is_terminates(effects)
+            removable = effect_free & nothrow & terminates
             return (consistent, removable, nothrow)
         elseif head === :new_opaque_closure
             length(args) < 4 && return (false, false, false)

test/compiler/irpasses.jl

@@ -1562,7 +1562,7 @@ function persistent_dict_elim_multiple()
 end
 @test_broken fully_eliminated(persistent_dict_elim_multiple)
 let code = code_typed(persistent_dict_elim_multiple)[1][1].code
-    @test count(x->isexpr(x, :invoke), code) == 0
+    @test_broken count(x->isexpr(x, :invoke), code) == 0
     @test code[end] == Core.ReturnNode(1)
 end
 
@@ -1781,3 +1781,37 @@ let code = Any[
     @test !any(iscall((ir, getfield)), ir.stmts.stmt)
     @test length(ir.cfg.blocks[end].stmts) == 1
 end
+
+# JuliaLang/julia#52991: statements that may not :terminate should not be deleted
+@noinline Base.@assume_effects :effect_free :nothrow function issue52991(n)
+    local s = 0
+    try
+        while true
+            yield()
+            if n - rand(1:10) > 0
+                s += 1
+            else
+                break
+            end
+        end
+    catch
+    end
+    return s
+end
+@test !Core.Compiler.is_removable_if_unused(Base.infer_effects(issue52991, (Int,)))
+let src = code_typed1(issue52991, (Int,))
+    @test count(isinvoke(:issue52991), src.code) == 0
+end
+let t = @async begin
+        issue52991(11) # this call never terminates
+        nothing
+    end
+    sleep(1)
+    if istaskdone(t)
+        ok = false
+    else
+        ok = true
+        schedule(t, InterruptException(); error=true)
+    end
+    @test ok
+end