make exp nothrow (JuliaLang#46238)

This change allows our compiler to remove dead calls of these math ops. Co-authored-by: Simeon Schaub <[email protected]> Co-authored-by: Shuhei Kadowaki <[email protected]>
halleysfifthinc · Aug 4, 2022 · bc4bb1b · bc4bb1b
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commit bc4bb1b
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Showing 2 changed files with 7 additions and 6 deletions.
diff --git a/base/special/exp.jl b/base/special/exp.jl
@@ -175,12 +175,10 @@ const J_TABLE = (0x0000000000000000, 0xaac00b1afa5abcbe, 0x9b60163da9fb3335, 0xa
  0xa66f0f9c1cb64129, 0x93af252b376bba97, 0xacdf3ac948dd7273, 0x99df50765b6e4540, 0x9faf6632798844f8,
  0xa12f7bfdad9cbe13, 0xaeef91d802243c88, 0x874fa7c1819e90d8, 0xacdfbdba3692d513, 0x62efd3c22b8f71f1, 0x74afe9d96b2a23d9)
 
-# XXX we want to mark :consistent-cy here so that this function can be concrete-folded,
-# because the effect analysis currently can't prove it in the presence of `@inbounds` or
-# `:boundscheck`, but still the access to `J_TABLE` is really safe here
-Base.@assume_effects :consistent @inline function table_unpack(ind::Int32)
+# :nothrow needed since the compiler can't prove `ind` is inbounds.
+Base.@assume_effects :nothrow @inline function table_unpack(ind::Int32)
  ind = ind & 255 + 1 # 255 == length(J_TABLE) - 1
- j = @inbounds J_TABLE[ind]
+ j = getfield(J_TABLE, ind) # use getfield so the compiler can prove consistent
  jU = reinterpret(Float64, JU_CONST | (j&JU_MASK))
  jL = reinterpret(Float64, JL_CONST | (j>>8))
  return jU, jL

diff --git a/test/math.jl b/test/math.jl
@@ -1461,7 +1461,10 @@ for fn in (:sin, :cos, :tan, :log, :log2, :log10, :log1p, :exponent, :sqrt, :cbr
  @test Core.Compiler.is_foldable(eff)
  end
 end
-for T in (Float32, Float64)
+for T in (Float16, Float32, Float64)
+ for f in (exp, exp2, exp10)
+ @test Core.Compiler.is_removable_if_unused(Base.infer_effects(f, (T,)))
+ end
  @test Core.Compiler.is_foldable(Base.infer_effects(^, (T,Int)))
  @test Core.Compiler.is_foldable(Base.infer_effects(^, (T,T)))
 end