From 24009bbd6d99b8c72d320effb9a3fbb0ac09600e Mon Sep 17 00:00:00 2001
From: xumingkuan <xumingkuan0721@126.com>
Date: Mon, 20 Apr 2020 19:13:10 -0400
Subject: [PATCH] [opt] Eliminate `WhileControlStmt` with non-zero const
 conditions

---
 taichi/transforms/alg_simp.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/taichi/transforms/alg_simp.cpp b/taichi/transforms/alg_simp.cpp
index ad8abff42d953..637c5b3f50924 100644
--- a/taichi/transforms/alg_simp.cpp
+++ b/taichi/transforms/alg_simp.cpp
@@ -74,6 +74,17 @@ class AlgSimp : public BasicStmtVisitor {
     }
   }
 
+  void visit(WhileControlStmt *stmt) override {
+    auto cond = stmt->cond->cast<ConstStmt>();
+    if (!cond)
+      return;
+    if (!alg_is_zero(cond)) {
+      // this statement has no effect
+      stmt->parent->erase(stmt);
+      throw IRModified();
+    }
+  }
+
   static bool alg_is_zero(ConstStmt *stmt) {
     if (!stmt)
       return false;