From bbefc8fe7e4ffa0a259bd73918e1b55836e0a73a Mon Sep 17 00:00:00 2001
From: Erwin Coumans <erwin.coumans@gmail.com>
Date: Mon, 13 Mar 2017 22:27:37 -0700
Subject: [PATCH] Apply temporary stack-memory optimization, thanks to Jim
 Tillander (old pull request 316
 https://github.com/bulletphysics/bullet3/pull/316) You can disable this in
 the build system, by adding preprocessor define
 'BT_DISABLE_STACK_TEMP_MEMORY'

---
 src/BulletCollision/BroadphaseCollision/btDbvt.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/BulletCollision/BroadphaseCollision/btDbvt.h b/src/BulletCollision/BroadphaseCollision/btDbvt.h
index 1ca175723..b5a001458 100644
--- a/src/BulletCollision/BroadphaseCollision/btDbvt.h
+++ b/src/BulletCollision/BroadphaseCollision/btDbvt.h
@@ -942,7 +942,13 @@ inline void		btDbvt::collideTV(	const btDbvtNode* root,
 		ATTRIBUTE_ALIGNED16(btDbvtVolume)		volume(vol);
 		btAlignedObjectArray<const btDbvtNode*>	stack;
 		stack.resize(0);
+#ifndef BT_DISABLE_STACK_TEMP_MEMORY
+		char tempmemory[SIMPLE_STACKSIZE*sizeof(const btDbvtNode*)];
+		stack.initializeFromBuffer(tempmemory, 0, SIMPLE_STACKSIZE);
+#else
 		stack.reserve(SIMPLE_STACKSIZE);
+#endif //BT_DISABLE_STACK_TEMP_MEMORY
+
 		stack.push_back(root);
 		do	{
 			const btDbvtNode*	n=stack[stack.size()-1];
@@ -1078,7 +1084,12 @@ inline void		btDbvt::rayTest(	const btDbvtNode* root,
 			int								depth=1;
 			int								treshold=DOUBLE_STACKSIZE-2;
 
+			char tempmemory[DOUBLE_STACKSIZE * sizeof(const btDbvtNode*)];
+#ifndef BT_DISABLE_STACK_TEMP_MEMORY
+			stack.initializeFromBuffer(tempmemory, DOUBLE_STACKSIZE, DOUBLE_STACKSIZE);
+#else//BT_DISABLE_STACK_TEMP_MEMORY
 			stack.resize(DOUBLE_STACKSIZE);
+#endif //BT_DISABLE_STACK_TEMP_MEMORY
 			stack[0]=root;
 			btVector3 bounds[2];
 			do	{