Make fastmath aware of Base.literal_pow.

Author: ajkeller34

base/fastmath.jl

@@ -113,6 +113,9 @@ function make_fastmath(expr::Expr)
                 $arrvar[$(indvars...)] = $op($arrvar[$(indvars...)], $rhs)
             end
         end
+    elseif is_literal_int_pow(expr)
+        expr = Expr(expr.head, :(Base.literal_pow),
+            expr.args[1], expr.args[2], Val(expr.args[3]))
     end
     Expr(make_fastmath(expr.head), map(make_fastmath, expr.args)...)
 end
@@ -150,6 +153,10 @@ macro fastmath(expr)
     make_fastmath(esc(expr))
 end
 
+function is_literal_int_pow(ex::Expr)
+    return (ex.head === :call && length(ex.args) == 3 &&
+        ex.args[1] === :^ && isa(ex.args[3], Integer))
+end
 
 # Basic arithmetic
 

test/fastmath.jl

@@ -202,3 +202,10 @@ let a = ones(2,2), b = ones(2,2)
     local c = 0
     @test @fastmath(c |= 1) == 1
 end
+
+struct LitPowTest end
+Base.literal_pow(::typeof(Base.FastMath.pow_fast), ::LitPowTest, ::Val{p}) where {p} = 1
+Base.literal_pow(::typeof(^), ::LitPowTest, ::Val{p}) where {p} = 2
+LPT = LitPowTest()
+@test (@fastmath LPT^2) == 1
+@test LPT^2 == 2