Fix allocation tests on Julia >= 1.13 (#536)

OpenLibm is a `Libdl.LazyLibrary` on Julia >= 1.13. Its `ccall` targets are
resolved on first use and cached per callsite, and resolving one allocates
16 bytes.

Each test measured a single call of a newly created closure, into which the
`ccall` is inlined by constant propagation. So every measurement included the
16 bytes of resolving a fresh callsite. Affected are the paths that call
`gamma` (`1 <= a <= 20`) or `erfc` (`a == 0.5`).

Now each closure is called twice and only the second measurement is used.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: devmotion

test/gamma_inc.jl

@@ -305,6 +305,14 @@ end
     @test_throws DomainError loggamma(6, -3.2)
 end
 
+# Run `f(args...)` twice and return only the result of the second call, so that
+# one-time costs of the first execution of a freshly compiled callsite are not
+# measured. On Julia >= 1.13 OpenLibm is a `Libdl.LazyLibrary`, so resolving the
+# target of a `ccall` into it allocates 16 bytes on that callsite's first
+# execution. Warming up with a separate call does not help, because the binding
+# is cached per callsite and not per callee.
+run_twice(f, args...) = (f(args...); f(args...))
+
 @testset "GPU compatibility ($FT)" for FT in (Float64, Float32, Float16)
     # Note: This test is a proxy for GPU compatibility by checking that the functions
     # are type stable and do not allocate memory. It does not launch any GPU kernels.
@@ -319,38 +327,38 @@ end
         # `@allocated` checks for allocations for specific code paths
         ## a >= 1
         ### gamma_inc_temme_1: simplified Temme expansion
-        @test iszero((FT -> @allocated(gamma_inc(FT(30.0), FT(29.99999), 0)))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(30.0), FT(29.99999), 0)), FT))
         ### gamma_inc_minimax: minimax approximation
-        @test iszero((FT -> @allocated(gamma_inc(FT(100.0), FT(80.0), 0)))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(100.0), FT(80.0), 0)), FT))
         ### gamma_inc_temme: Temme expansion
-        @test iszero((FT -> @allocated(gamma_inc(FT(100.0), FT(80.0), 1)))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(100.0), FT(80.0), 1)), FT))
         ### gamma_inc_cf: Continued fraction
-        @test iszero((FT -> @allocated(gamma_inc(FT(1.7), FT(2.5))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(1.7), FT(2.5))), FT))
         ### gamma_inc_taylor: Taylor series
-        @test iszero((FT -> @allocated(gamma_inc(FT(11.1), FT(0.001))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(11.1), FT(0.001))), FT))
         ### gamma_inc_asym: Asymptotic expansion
-        @test iszero((FT -> @allocated(gamma_inc(FT(10.0), FT(35.0))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(10.0), FT(35.0))), FT))
         ### gamma_inc_fsum: Finite sums
-        @test iszero((FT -> @allocated(gamma_inc(FT(24.0), FT(25))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(24.0), FT(25))), FT))
         ## a==0.5
         ### erfc
-        @test iszero((FT -> @allocated(gamma_inc(FT(0.5), FT(0.5))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(0.5), FT(0.5))), FT))
         ## x < 1.1
         ### gamma_inc_taylor_x
-        @test iszero((FT -> @allocated(gamma_inc(FT(0.9), FT(0.8))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(0.9), FT(0.8))), FT))
         ## else
         ### gamma_inc_cf
-        @test iszero((FT -> @allocated(gamma_inc(FT(0.7), FT(2.5))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc(FT(0.7), FT(2.5))), FT))
     end
 
     @testset "gamma_inc_inv allocations" begin
         # `@allocated` checks for allocations for specific code paths
         ## x0 approximation paths
         ### gamma_inc_inv_psmall
-        @test iszero((FT -> @allocated(gamma_inc_inv(FT(1.0), FT(0.01), FT(0.99))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc_inv(FT(1.0), FT(0.01), FT(0.99))), FT))
         ### gamma_inc_inv_qsmall
-        @test iszero((FT -> @allocated(gamma_inc_inv(FT(5.0), FT(0.99), FT(0.01))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc_inv(FT(5.0), FT(0.99), FT(0.01))), FT))
         ### gamma_inc_inv_alarge
-        @test iszero((FT -> @allocated(gamma_inc_inv(FT(50.0), FT(0.3), FT(0.7))))(FT))
+        @test iszero(run_twice(FT -> @allocated(gamma_inc_inv(FT(50.0), FT(0.3), FT(0.7))), FT))
     end
 end