From ff41359014aa0c2965c151c699bd888ea1478b87 Mon Sep 17 00:00:00 2001
From: Vincent Laviron <vincent.laviron@gmail.com>
Date: Tue, 5 Oct 2021 11:01:54 +0200
Subject: Enable if-then-else elimination in Cmmgen

---
 asmcomp/cmmgen.ml | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/asmcomp/cmmgen.ml b/asmcomp/cmmgen.ml
index 3876da2e60..ac4f47771c 100644
--- a/asmcomp/cmmgen.ml
+++ b/asmcomp/cmmgen.ml
@@ -609,8 +609,16 @@ let rec transl env e =
       let ifso_dbg = Debuginfo.none in
       let ifnot_dbg = Debuginfo.none in
       let dbg = Debuginfo.none in
-      transl_if env Unknown dbg cond
-        ifso_dbg (transl env ifso) ifnot_dbg (transl env ifnot)
+      let ifso = transl env ifso in
+      let ifnot = transl env ifnot in
+      let approx =
+        match ifso, ifnot with
+        | Cconst_int (1, _), Cconst_int (3, _) -> Then_false_else_true
+        | Cconst_int (3, _), Cconst_int (1, _) -> Then_true_else_false
+        | _, _ -> Unknown
+      in
+      transl_if env approx dbg cond
+        ifso_dbg ifso ifnot_dbg ifnot
   | Usequence(exp1, exp2) ->
       Csequence(remove_unit(transl env exp1), transl env exp2)
   | Uwhile(cond, body) ->
-- 
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