From 3f93ecbc6dbdc315b79de4ee69bf6bc6a6420d57 Mon Sep 17 00:00:00 2001
From: Alasdair Armstrong
Date: Thu, 3 May 2018 15:30:55 +0100
Subject: Flow typing and l-expression changes for ASL parser

1. Experiment with allowing some flow typing on mutable variables for
translating ASL in a more idiomatic way. I realise after updating some
of the test cases that this could have some problematic side effects
for lem translation, where mutable variables are translated into
monadic code. We'd need to ensure that whatever flow typing happens
for mutable variables also works for monadic code, including within
transformed loops. If this doesn't work out some of these changes may
need to be reverted.

2. Make the type inference for l-expressions a bit smarter. Splits the
type checking rules for l-expressions into a inference part and a
checking part like the other bi-directional rules. Should not be able
to type check slightly more l-expresions, such as nested vector slices
that may not have checked previously.

The l-expression rules for vector patterns should be simpler now, but
they are also more strict about bounds checking. Previously the bounds
checks were derived from the corresponding operations that would
appear on the RHS (i.e. LEXP_vector would get it's check from
vector_access). This meant that the l-expression bounds checks could
be weakend by weakening the checks on those operations. Now this is no
longer possible, there is a -no_lexp_bounds_check option which turns
of bounds checking in l-expressions. Currently this is on for the
generated ARM spec, but this should only be temporary.

3. Add a LEXP_vector_concat which mirrors P_vector_concat except in
l-expressions. Previously there was a hack that overloaded LEXP_tup
for this to translate some ASL patterns, but that was fairly
ugly. Adapt the rewriter and other parts of the code to handle
this. The rewriter for lexp tuple vector assignments is now a rewriter
for vector concat assignments.

4. Include a newly generated version of aarch64_no_vector

5. Update the Ocaml test suite to use builtins in lib/
---
 src/parse_ast.ml | 1 +
 1 file changed, 1 insertion(+)

(limited to 'src/parse_ast.ml')

diff --git a/src/parse_ast.ml b/src/parse_ast.ml
index 826d8eb1..55ed57d2 100644
--- a/src/parse_ast.ml
+++ b/src/parse_ast.ml
@@ -517,6 +517,7 @@ lexp_aux =  (* lvalue expression, can't occur out of the parser *)
  | LEXP_mem of id * (exp) list
  | LEXP_vector of lexp * exp (* vector element *)
  | LEXP_vector_range of lexp * exp * exp (* subvector *)
+ | LEXP_vector_concat of lexp list
  | LEXP_field of lexp * id (* struct field *)
 
 and lexp = 
-- 
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