From 20e2041f14f8ebb842df4ebdac9ba3dc0955e670 Mon Sep 17 00:00:00 2001
From: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Date: Sat, 2 May 2015 15:57:46 -0700
Subject: Reorder conditions in compact_string implementation

Now compact_string matches compact_pointer_parent.

Turns out PUGI__UNLIKELY is good at reordering conditions but usually does not
really affect performance. Since MSVC should treat "if" branches as taken and
does not support branch probabilities, don't use them if we don't need to.
---
 src/pugixml.cpp | 58 ++++++++++++++++++++++++++++-----------------------------
 1 file changed, 28 insertions(+), 30 deletions(-)

(limited to 'src')

diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index 1a7acb3..568eb17 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -849,7 +849,7 @@ PUGI__NS_BEGIN
 				{
 					xml_memory_page* page = compact_get_page(this, header_offset);
 
-					if (page->compact_shared_parent == 0)
+					if (PUGI__UNLIKELY(page->compact_shared_parent == 0))
 						page->compact_shared_parent = value;
 
 					if (page->compact_shared_parent == value)
@@ -872,17 +872,15 @@ PUGI__NS_BEGIN
 
 		operator T*() const
 		{
-			int data = _data;
-
-			if (data)
+			if (_data)
 			{
-				if (data < 65534)
+				if (_data < 65534)
 				{
 					uintptr_t base = reinterpret_cast<uintptr_t>(this) & ~(compact_alignment - 1);
 
-					return reinterpret_cast<T*>(base + ((data - 1 - 65533) << compact_alignment_log2));
+					return reinterpret_cast<T*>(base + ((_data - 1 - 65533) << compact_alignment_log2));
 				}
-				else if (data == 65534)
+				else if (_data == 65534)
 					return static_cast<T*>(compact_get_page(this, header_offset)->compact_shared_parent);
 				else
 					return compact_get_value<header_offset, T>(this);
@@ -923,36 +921,36 @@ PUGI__NS_BEGIN
 
 				ptrdiff_t offset = value - page->compact_string_base;
 
-				if (PUGI__UNLIKELY(static_cast<uintptr_t>(offset) >= (65535 << 7)))
-				{
-					compact_set_value<header_offset>(this, value);
-
-					_data = 255;
-				}
-				else
+				if (static_cast<uintptr_t>(offset) < (65535 << 7))
 				{
 					uint16_t* base = reinterpret_cast<uint16_t*>(reinterpret_cast<char*>(this) - base_offset);
 
-					if (PUGI__UNLIKELY(*base))
+					if (*base == 0)
+					{
+						*base = static_cast<uint16_t>((offset >> 7) + 1);
+						_data = static_cast<unsigned char>((offset & 127) + 1);
+					}
+					else
 					{
 						ptrdiff_t remainder = offset - ((*base - 1) << 7);
 
-						if (PUGI__UNLIKELY(static_cast<uintptr_t>(remainder) >= 254))
+						if (static_cast<uintptr_t>(remainder) < 254)
 						{
-							compact_set_value<header_offset>(this, value);
-
-							_data = 255;
+							_data = static_cast<unsigned char>(remainder + 1);
 						}
 						else
 						{
-							_data = static_cast<unsigned char>(remainder + 1);
+							compact_set_value<header_offset>(this, value);
+
+							_data = 255;
 						}
 					}
-					else
-					{
-						*base = static_cast<uint16_t>((offset >> 7) + 1);
-						_data = static_cast<unsigned char>((offset & 127) + 1);
-					}
+				}
+				else
+				{
+					compact_set_value<header_offset>(this, value);
+
+					_data = 255;
 				}
 			}
 			else
@@ -965,11 +963,7 @@ PUGI__NS_BEGIN
 		{
 			if (_data)
 			{
-				if (PUGI__UNLIKELY(_data == 255))
-				{
-					return compact_get_value<header_offset, char_t>(this);
-				}
-				else
+				if (_data < 255)
 				{
 					xml_memory_page* page = compact_get_page(this, header_offset);
 
@@ -980,6 +974,10 @@ PUGI__NS_BEGIN
 
 					return page->compact_string_base + offset;
 				}
+				else
+				{
+					return compact_get_value<header_offset, char_t>(this);
+				}
 			}
 			else
 				return 0;
-- 
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