Merge pull request #8624 from JuliaLang/jcb/cfsimd

Reject `@simd` loops with break / continue / `@goto` in inner loop body

NEWS.md

@@ -74,6 +74,8 @@ Library improvements
   * New `ordschur` and `ordschur!` functions for sorting a schur factorization by the eigenvalues.
 
   * `deepcopy` recurses through immutable types and makes copies of their mutable fields ([#8560]).
+
+  * `@simd` now rejects invalid control flow (`@goto` / break / continue) in the inner loop body at compile time ([#8624]).
 
   * Givens type doesn't have a size anymore and is no longer a subtype of AbstractMatrix ([#8660])
 

base/simdloop.jl

@@ -19,10 +19,26 @@ function parse_iteration_space(x)
     x.args # symbol, range
 end
 
+# reject invalid control flow statements in @simd loop body
+function check_body!(x::Expr)
+    if x.head === :break || x.head == :continue
+        throw(SimdError("$(x.head) is not allowed inside a @simd loop body"))
+    elseif x.head === :macrocall && x.args[1] === symbol("@goto")
+        throw(SimdError("$(x.args[1]) is not allowed inside a @simd loop body"))
+    end
+    for arg in x.args
+        check_body!(arg)
+    end
+    return true
+end
+check_body!(x::QuoteNode) = check_body!(x.value)
+check_body!(x) = true
+
 # Compile Expr x in context of @simd.
 function compile(x)
     (isa(x, Expr) && x.head == :for) || throw(SimdError("for loop expected"))
     length(x.args) == 2 || throw(SimdError("1D for loop expected"))
+    check_body!(x)
 
     var,range = parse_iteration_space(x.args[1])
     r = gensym("r") # Range value

test/simdloop.jl

@@ -67,3 +67,26 @@ let j=4
     end
     @test !simd_loop_local_present
 end
+
+import Base.SimdLoop.SimdError
+
+# Test that @simd rejects inner loop body with invalid control flow statements
+# issue #8613
+@test_throws SimdError eval(:(begin
+    @simd for x = 1:10
+        x == 1 && break
+    end
+end))
+
+@test_throws SimdError eval(:(begin
+    @simd for x = 1:10
+        x < 5 && continue
+    end
+end))
+
+@test_throws SimdError eval(:(begin
+    @simd for x = 1:10
+        x == 1 || @goto exit_loop
+    end
+    @label exit_loop
+end))