From 2273d84fd1081d9e12f65398b9f1936b357b56ad Mon Sep 17 00:00:00 2001
From: Laurent Le Brun <laurentlb@gmail.com>
Date: Sat, 12 Nov 2022 20:41:31 +0100
Subject: [PATCH] Fix stackoverflow error in simplifyExpr (#165)

This was caused by trying to reorder multiple arguments back and forth
---
 src/rewriter.fs               | 8 ++++----
 tests/unit/operators.expected | 4 ++++
 tests/unit/operators.frag     | 4 ++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/rewriter.fs b/src/rewriter.fs
index e7076fa3..e91b0135 100644
--- a/src/rewriter.fs
+++ b/src/rewriter.fs
@@ -78,7 +78,7 @@ let private inlineFn (declArgs:Decl list) passedArgs bodyExpr =
 
 /// Expression that doesn't need parentheses around it.
 let (|NoParen|_|) = function
-    | Int _ | Float _ | Dot _ | Var _ | FunCall _ | Subscript _ as x -> Some x
+    | Int _ | Float _ | Dot _ | Var _ | FunCall (Var _, _) | Subscript _ as x -> Some x
     | _ -> None
 
 let rec private simplifyExpr (didInline: bool ref) env = function
@@ -108,7 +108,7 @@ let rec private simplifyExpr (didInline: bool ref) env = function
     | FunCall(Op "-", [x; Int (i, s)]) when i < 0 ->
         FunCall(Op "+", [x; Int (-i, s)]) |> env.fExpr env
 
-    // Swap operands to get rid of parenthese
+    // Swap operands to get rid of parentheses
     // x*(y*z) -> y*z*x
     | FunCall(Op "*", [NoParen x; FunCall(Op "*", [y; z])]) ->
         FunCall(Op "*", [FunCall(Op "*", [y; z]); x]) |> env.fExpr env
@@ -117,10 +117,10 @@ let rec private simplifyExpr (didInline: bool ref) env = function
     | FunCall(Op "+", [NoParen x; FunCall(Op ("+"|"-") as op, [y; z])]) ->
         FunCall(Op "+", [FunCall(op, [y; z]); x]) |> env.fExpr env
     // x-(y+z) -> x-y-z
-    | FunCall(Op "-", [NoParen x; FunCall(Op "+", [y; z])]) ->
+    | FunCall(Op "-", [x; FunCall(Op "+", [y; z])]) ->
         FunCall(Op "-", [FunCall(Op "-", [x; y]); z]) |> env.fExpr env
     // x-(y-z) -> x-y+z
-    | FunCall(Op "-", [NoParen x; FunCall(Op "-", [y; z])]) ->
+    | FunCall(Op "-", [x; FunCall(Op "-", [y; z])]) ->
         FunCall(Op "+", [FunCall(Op "-", [x; y]); z]) |> env.fExpr env
 
     // Boolean simplifications (let's ignore the suffix)
diff --git a/tests/unit/operators.expected b/tests/unit/operators.expected
index ad01da30..ce261155 100644
--- a/tests/unit/operators.expected
+++ b/tests/unit/operators.expected
@@ -20,4 +20,8 @@
  "{"
    "int d=b*c*a;"
    "return a-b+1-d+c;"
+ "}"
+ "int other(int a,int b,int c,int d)"
+ "{"
+   "return a*b*(c*d)*(a*b);"
  "}",
diff --git a/tests/unit/operators.frag b/tests/unit/operators.frag
index bfb82ece..777a68e8 100644
--- a/tests/unit/operators.frag
+++ b/tests/unit/operators.frag
@@ -20,3 +20,7 @@ int no_parens2(int a, int b, int c) {
 	int d = a*(b*c);
 	return a - (b - 1) - (d - c);
 }
+
+int other(int a, int b, int c, int d) {
+    return (a*b)*(c*d)*(a*b);
+}