Improve integer exponentation fallback.

lib/intrinsics/Project.toml

@@ -1,7 +1,7 @@
 name = "SPIRVIntrinsics"
 uuid = "71d1d633-e7e8-4a92-83a1-de8814b09ba8"
 authors = ["Tim Besard <tim.besard@gmail.com>"]
-version = "0.5.8"
+version = "0.5.9"
 
 [deps]
 ExprTools = "e2ba6199-217a-4e67-a87a-7c52f15ade04"

lib/intrinsics/src/math.jl

@@ -189,30 +189,32 @@ end
 # through Float64 (broken on backends without FP64) and in all cases leaves a
 # runtime `pown` in the generated code. Mark the override `:foldable` so
 # literal expressions like `Float32(2)^(-32)` const-fold to a compile-time
-# constant, and recurse into the existing `::Int32` overrides for the tail.
+# constant, and fall back to the float-exponent `pow` for the tail (matches
+# Base's own fallback for out-of-range integer exponents since 1.12; see
+# `base/special/pow.jl`).
 @device_override @assume_effects :foldable @inline function Base.:(^)(x::Float16, y::Int64)
     y == -1 && return inv(x)
     y == 0  && return one(x)
     y == 1  && return x
     y == 2  && return x * x
     y == 3  && return x * x * x
-    x ^ (y % Int32)
+    x ^ Float16(y)
 end
 @device_override @assume_effects :foldable @inline function Base.:(^)(x::Float32, y::Int64)
     y == -1 && return inv(x)
     y == 0  && return one(x)
     y == 1  && return x
     y == 2  && return x * x
     y == 3  && return x * x * x
-    x ^ (y % Int32)
+    x ^ Float32(y)
 end
 @device_override @assume_effects :foldable @inline function Base.:(^)(x::Float64, y::Int64)
     y == -1 && return inv(x)
     y == 0  && return one(x)
     y == 1  && return x
     y == 2  && return x * x
     y == 3  && return x * x * x
-    x ^ (y % Int32)
+    x ^ Float64(y)
 end
 
 # remquo(x::Float32{n}, y::Float32{n}, Int32{n} *quo) = @builtin_ccall("remquo", Float32{n}, (Float32{n}, Float32{n}, Int32{n} *), x, y, quo)

test/intrinsics.jl

@@ -126,6 +126,17 @@ end
     end
 end
 
+# Regression test for #428: `^(::Float, ::Int64)` must not truncate the
+# exponent through Int32, since `y % Int32` wraps for |y| ≥ 2^31 and would
+# flip the sign of the exponent (producing 0 instead of Inf, etc.).
+@testset "^(::$T, ::Int64) with out-of-Int32 exponent" for T in float_types
+    y = Int64(typemax(Int32)) + Int64(1)  # smallest Int64 not representable as Int32
+    for x in (T(1.5), T(0.5))
+        @test call_on_device(^, x, y) === x ^ y
+        @test call_on_device(^, x, -y) === x ^ -y
+    end
+end
+
 @testset "OpenCL-specific unary - $T" for T in float_types
     @testset "$f" for f in [
             OpenCL.acospi,