From e3aa6935bfe7bb1e92a5c70f3df4bd380149d03c Mon Sep 17 00:00:00 2001
From: Alasdair Armstrong
Date: Sat, 20 Apr 2019 11:58:53 +0100
Subject: Fix: Reduce constant-fold time for ARM from 20min+ to 10s

With the new interpreter changes computing the initial state for the
interpreter does some significant work. The existing code was
re-computing the initial state for every subexpression in the
specification (not even just the ones due to be constant-folded away).
Now we just compute the initial state once and use it for all constant
folds.

Also reduce the time taken for the simple_assignments rewrite from 20s
to under 1s for ARMv8.5, by skipping l-expressions that are already in
the simplest form.
---
 src/constant_fold.ml | 3 ++-
 src/rewrites.ml      | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/constant_fold.ml b/src/constant_fold.ml
index 14d6550c..f2e0add5 100644
--- a/src/constant_fold.ml
+++ b/src/constant_fold.ml
@@ -251,10 +251,11 @@ let rec rewrite_constant_function_calls' ast =
   let rewrite_count = ref 0 in
   let ok () = incr rewrite_count in
   let not_ok () = decr rewrite_count in
+  let istate = initial_state ast Type_check.initial_env in
 
   let rw_defs = {
       rewriters_base with
-      rewrite_exp = (fun _ -> rw_exp ok not_ok (initial_state ast Type_check.initial_env))
+      rewrite_exp = (fun _ -> rw_exp ok not_ok istate)
     } in
   let ast = rewrite_defs_base rw_defs ast in
   (* We keep iterating until we have no more re-writes to do *)
diff --git a/src/rewrites.ml b/src/rewrites.ml
index 34d45618..a37449a4 100644
--- a/src/rewrites.ml
+++ b/src/rewrites.ml
@@ -2153,6 +2153,10 @@ let rewrite_simple_assignments env defs =
   let assign_e_aux e_aux annot =
     let env = env_of_annot annot in
     match e_aux with
+    | E_assign (LEXP_aux (LEXP_id _, _), _) ->
+       E_aux (e_aux, annot)
+    | E_assign (LEXP_aux (LEXP_cast (_, _), _), _) ->
+       E_aux (e_aux, annot)
     | E_assign (lexp, exp) ->
        let (lexp, rhs) = rewrite_lexp_to_rhs lexp in
        let assign = mk_exp (E_assign (strip_lexp lexp, strip_exp (rhs exp))) in
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