From 7c4afbf358f4f8dd20d66c993d28452e1eea160c Mon Sep 17 00:00:00 2001
From: Shuhei Kadowaki <aviatesk@gmail.com>
Date: Thu, 24 Nov 2022 16:16:43 +0900
Subject: [PATCH] inference: mark flag for effect-free `:call`s during
 abstractinterpret

So that they can be deleted during the first `compact!`-ion.
This allows us to delete an inlineable and effect-free, but unused call.

This is essentially an alternative of #47305, but doesn't introduce a
problem like #47374.
---
 base/compiler/abstractinterpretation.jl |  6 ++++++
 base/compiler/inferencestate.jl         |  2 ++
 test/compiler/inline.jl                 | 23 +++++++++++++++++++++--
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/base/compiler/abstractinterpretation.jl b/base/compiler/abstractinterpretation.jl
index 0fb85c4d00d1a2..8ecb690880b0d5 100644
--- a/base/compiler/abstractinterpretation.jl
+++ b/base/compiler/abstractinterpretation.jl
@@ -2243,6 +2243,12 @@ function abstract_eval_statement_expr(interp::AbstractInterpreter, e::Expr, vtyp
             merge_effects!(interp, sv, effects)
             if isa(sv, InferenceState)
                 sv.stmt_info[sv.currpc] = info
+                # mark this call statement as DCE-elgible
+                if is_removable_if_unused(effects)
+                    add_curr_ssaflag!(sv, IR_FLAG_EFFECT_FREE)
+                else
+                    sub_curr_ssaflag!(sv, IR_FLAG_EFFECT_FREE)
+                end
             end
         end
         t = rt
diff --git a/base/compiler/inferencestate.jl b/base/compiler/inferencestate.jl
index 49315fd67834c0..d7d06757ded2e3 100644
--- a/base/compiler/inferencestate.jl
+++ b/base/compiler/inferencestate.jl
@@ -537,6 +537,8 @@ function print_callstack(sv::InferenceState)
 end
 
 get_curr_ssaflag(sv::InferenceState) = sv.src.ssaflags[sv.currpc]
+add_curr_ssaflag!(sv::InferenceState, flag::UInt8) = sv.src.ssaflags[sv.currpc] |= flag
+sub_curr_ssaflag!(sv::InferenceState, flag::UInt8) = sv.src.ssaflags[sv.currpc] &= ~flag
 
 function narguments(sv::InferenceState)
     def = sv.linfo.def
diff --git a/test/compiler/inline.jl b/test/compiler/inline.jl
index 1119c6d01b8e9e..8de005a9ef48d4 100644
--- a/test/compiler/inline.jl
+++ b/test/compiler/inline.jl
@@ -1077,8 +1077,7 @@ Base.setindex!(s::SafeRef, x) = setfield!(s, 1, x)
     noninlined_dce_new(s)
     nothing
 end
-# should be resolved once we merge https://github.com/JuliaLang/julia/pull/43923
-@test_broken fully_eliminated((Union{Symbol,String},)) do s
+@test fully_eliminated((Union{Symbol,String},)) do s
     noninlined_dce_new(s)
     nothing
 end
@@ -1817,6 +1816,26 @@ let ir = Base.code_ircode(big_tuple_test1, Tuple{})[1][1]
     @test length(ir.stmts) == 1
 end
 
+# inlineable but removable call should be eligible for DCE
+Base.@assume_effects :removable @inline function inlineable_effect_free(a::Float64)
+    a == Inf && return zero(a)
+    return sin(a) + cos(a)
+end
+@test fully_eliminated((Float64,)) do a
+    b = inlineable_effect_free(a)
+    c = inlineable_effect_free(b)
+    nothing
+end
+
+# https://github.com/JuliaLang/julia/issues/47374
+function f47374(x)
+    [f47374(i, x) for i in 1:1]
+end
+function f47374(i::Int, x)
+    return 1.0
+end
+@test f47374(rand(1)) == Float64[1.0]
+
 # compiler should recognize effectful :static_parameter
 # https://github.com/JuliaLang/julia/issues/45490
 issue45490_1(x::Union{T, Nothing}, y::Union{T, Nothing}) where {T} = T