From 51258295bd41ab76de7a422f53ae81556dc1009f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Gardou?= <jerome.gardou@reactos.org>
Date: Thu, 24 Jun 2021 11:41:24 +0200
Subject: [PATCH] [NTOS:KE] Rewrite KeZeroPages in assembly

We spend a lot of time in this function, let's optimize it.
---
 ntoskrnl/ke/i386/cpu.c      |  9 ---------
 ntoskrnl/ke/i386/zeropage.S | 32 ++++++++++++++++++++++++++++++++
 ntoskrnl/ntos.cmake         |  1 +
 3 files changed, 33 insertions(+), 9 deletions(-)
 create mode 100644 ntoskrnl/ke/i386/zeropage.S

diff --git a/ntoskrnl/ke/i386/cpu.c b/ntoskrnl/ke/i386/cpu.c
index bdc92f908fd..ac1d9ee4dfd 100644
--- a/ntoskrnl/ke/i386/cpu.c
+++ b/ntoskrnl/ke/i386/cpu.c
@@ -1133,15 +1133,6 @@ KeInvalidateAllCaches(VOID)
     return TRUE;
 }
 
-VOID
-FASTCALL
-KeZeroPages(IN PVOID Address,
-            IN ULONG Size)
-{
-    /* Not using XMMI in this routine */
-    RtlZeroMemory(Address, Size);
-}
-
 VOID
 NTAPI
 KiSaveProcessorState(IN PKTRAP_FRAME TrapFrame,
diff --git a/ntoskrnl/ke/i386/zeropage.S b/ntoskrnl/ke/i386/zeropage.S
new file mode 100644
index 00000000000..c999b22eec1
--- /dev/null
+++ b/ntoskrnl/ke/i386/zeropage.S
@@ -0,0 +1,32 @@
+/*
+ * PROJECT:     ReactOS Kernel
+ * LICENSE:     GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
+ * PURPOSE:     Fast zeroing of pages
+ * COPYRIGHT:   Copyright 2021 Jérôme Gardou <jerome.gardou@reactos.org>
+ */
+
+#include <asm.inc>
+
+/* FUNCTIONS ****************************************************************/
+.code
+
+/*
+ * VOID
+ * FASTCALL
+ * KeZeroPages(void* ptr, ULONG Size)
+ */
+PUBLIC @KeZeroPages@8
+FUNC @KeZeroPages@8
+    FPO 0, 0, 0, 0, 0, FRAME_FPO
+
+    push edi
+    mov edi, ecx
+    mov ecx, edx
+    shr ecx, 2
+    xor eax, eax
+    rep stosd
+    pop edi
+    ret
+ENDFUNC
+
+END
diff --git a/ntoskrnl/ntos.cmake b/ntoskrnl/ntos.cmake
index 4b56e74896e..7803e4c812e 100644
--- a/ntoskrnl/ntos.cmake
+++ b/ntoskrnl/ntos.cmake
@@ -298,6 +298,7 @@ if(ARCH STREQUAL "i386")
         ${REACTOS_SOURCE_DIR}/ntoskrnl/ke/i386/ctxswitch.S
         ${REACTOS_SOURCE_DIR}/ntoskrnl/ke/i386/trap.s
         ${REACTOS_SOURCE_DIR}/ntoskrnl/ke/i386/usercall_asm.S
+        ${REACTOS_SOURCE_DIR}/ntoskrnl/ke/i386/zeropage.S
         ${REACTOS_SOURCE_DIR}/ntoskrnl/rtl/i386/stack.S)
     list(APPEND SOURCE
         ${REACTOS_SOURCE_DIR}/ntoskrnl/config/i386/cmhardwr.c