Take advantage of Cmaskzero and Cmasknotzero.

git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1825 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e

2 files changed, 30 insertions, 0 deletions

diff --git a/ia32/SelectOp.vp b/ia32/SelectOp.vp
index 98db3885..62de4ce1 100644
--- a/ia32/SelectOp.vp
+++ b/ia32/SelectOp.vp
@@ -429,3 +429,10 @@ Nondetfunction addressing (chunk: memory_chunk) (e: expr) :=
   | _ => (Aindexed Int.zero, e:::Enil)
   end.
 
+(** ** Turning an expression into a condition *)
+
+Nondetfunction cond_of_expr (e: expr) :=
+  match e with
+  | Eop (Oandimm n) (t1:::Enil) => (Cmasknotzero n, t1:::Enil)
+  | _ => (Ccompuimm Cne Int.zero, e:::Enil)
+  end.
diff --git a/ia32/SelectOpproof.v b/ia32/SelectOpproof.v
index e6fd8098..658a7550 100644
--- a/ia32/SelectOpproof.v
+++ b/ia32/SelectOpproof.v
@@ -753,4 +753,27 @@ Proof.
   exists (v :: nil); split. constructor; auto. constructor. subst; simpl. rewrite Int.add_zero; auto. 
 Qed.
 
+Theorem eval_cond_of_expr:
+  forall le a v b,
+  eval_expr ge sp e m le a v ->
+  Val.bool_of_val v b ->
+  match cond_of_expr a with (cond, args) =>
+    exists vl,
+    eval_exprlist ge sp e m le args vl /\
+    eval_condition cond vl m = Some b
+  end.
+Proof.
+  intros until v. unfold cond_of_expr; case (cond_of_expr_match a); intros; InvEval.
+  subst v. exists (v1 :: nil); split; auto with evalexpr.
+  simpl. destruct b.
+  generalize (Val.bool_of_true_val2 _ H0); clear H0; intro ISTRUE.
+  destruct v1; simpl in ISTRUE; try contradiction. 
+  rewrite Int.eq_false; auto.
+  generalize (Val.bool_of_false_val2 _ H0); clear H0; intro ISFALSE.
+  destruct v1; simpl in ISFALSE; try contradiction.
+  rewrite ISFALSE. rewrite Int.eq_true; auto.
+  exists (v :: nil); split; auto with evalexpr.
+  simpl. inversion H0; simpl. rewrite Int.eq_false; auto. auto. auto. 
+Qed.
+
 End CMCONSTR.