From 5a206276092d9eb56a8832ab131ec176b5a38a07 Mon Sep 17 00:00:00 2001
From: Sir Richard <sir_richard@svn.reactos.org>
Date: Sat, 30 Jan 2010 19:10:22 +0000
Subject: [PATCH] [NTOS]: Simplify KiTrapStub and write registers in order.
 [PERF]: Change instructions used to save registers on the trap frame to fix
 some WaW and RaW hazards.

svn path=/trunk/; revision=45354
---
 reactos/ntoskrnl/include/internal/trap_x.h | 43 ++++++++++------------
 1 file changed, 19 insertions(+), 24 deletions(-)

diff --git a/reactos/ntoskrnl/include/internal/trap_x.h b/reactos/ntoskrnl/include/internal/trap_x.h
index 1340c44c136..8eaee7a3dea 100644
--- a/reactos/ntoskrnl/include/internal/trap_x.h
+++ b/reactos/ntoskrnl/include/internal/trap_x.h
@@ -798,47 +798,42 @@ KiTrapStub(IN ULONG Flags,
     /* Software traps need to get their EIP from the caller's frame */
     if (Flags & KI_SOFTWARE_TRAP) __asm__ __volatile__ ("popl %%eax\n":::"%esp");
     
-    /* Now go ahead and make space for this frame */
-    __asm__ __volatile__ ("subl $%c[e],%%esp\n":: [e] "i"(FrameSize) : "%esp");
-        
-    /* Does the caller want volatiles only? */
-    if (Flags & KI_NONVOLATILES_ONLY) __asm__ __volatile__
+    /* Save nonvolatile registers */
+    __asm__ __volatile__
     (
-        /* Then only EBX, ESI, EDI and EBP are saved */
+        /* EBX, ESI, EDI and EBP are saved */
+        "movl %%ebp, %c[p](%%esp)\n"
         "movl %%ebx, %c[b](%%esp)\n"
         "movl %%esi, %c[s](%%esp)\n"
         "movl %%edi, %c[i](%%esp)\n"
-        "movl %%ebp, %c[p](%%esp)\n"
         :
-        : [b] "i"(FIELD_OFFSET(KTRAP_FRAME, Ebx)),
-          [s] "i"(FIELD_OFFSET(KTRAP_FRAME, Esi)),
-          [i] "i"(FIELD_OFFSET(KTRAP_FRAME, Edi)),
-          [p] "i"(FIELD_OFFSET(KTRAP_FRAME, Ebp))
+        : [b] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Ebx)),
+          [s] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Esi)),
+          [i] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Edi)),
+          [p] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Ebp))
         : "%esp"
     );
-    else __asm__ __volatile__
+    
+    /* Does the caller want nonvolatiles only? */
+    if (!(Flags & KI_NONVOLATILES_ONLY)) __asm__ __volatile__
     (
-        /* Otherwise, we save all the registers (except ESP) */
+        /* Otherwise, save the volatiles as well */
         "movl %%eax, %c[a](%%esp)\n"
-        "movl %%ebx, %c[b](%%esp)\n"
         "movl %%ecx, %c[c](%%esp)\n"
         "movl %%edx, %c[d](%%esp)\n"
-        "movl %%esi, %c[s](%%esp)\n"
-        "movl %%edi, %c[i](%%esp)\n"
-        "movl %%ebp, %c[p](%%esp)\n"
         :
-        : [a] "i"(FIELD_OFFSET(KTRAP_FRAME, Eax)),
-          [b] "i"(FIELD_OFFSET(KTRAP_FRAME, Ebx)),
-          [c] "i"(FIELD_OFFSET(KTRAP_FRAME, Ecx)),
-          [d] "i"(FIELD_OFFSET(KTRAP_FRAME, Edx)),
-          [s] "i"(FIELD_OFFSET(KTRAP_FRAME, Esi)),
-          [i] "i"(FIELD_OFFSET(KTRAP_FRAME, Edi)),
-          [p] "i"(FIELD_OFFSET(KTRAP_FRAME, Ebp))
+        : [a] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Eax)),
+          [c] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Ecx)),
+          [d] "i"(- FrameSize + FIELD_OFFSET(KTRAP_FRAME, Edx))
         : "%esp"
     );
 
     /* Now set parameter 1 (ECX) to point to the frame */
     __asm__ __volatile__ ("movl %%esp, %%ecx\n":::"%esp");
+    
+    /* Now go ahead and make space for this frame */
+    __asm__ __volatile__ ("subl $%c[e],%%esp\n":: [e] "i"(FrameSize) : "%esp");
+    __asm__ __volatile__ ("subl $%c[e],%%ecx\n":: [e] "i"(FrameSize) : "%ecx");
        
     /* For Fast-V86 traps, set parameter 2 (EDX) to hold EFlags */   
     if (Flags & KI_FAST_V86_TRAP) __asm__ __volatile__