[x86] Fix for Large Pages

Reload rcx register prior to calling OS_VirtualAlloc. This patch should prevent the rcx register from getting clobbered and therefore restore the functionality of LP in asmFish. See discussion at issue #160 for more details. Thanks to Moha for this correction.
lantonov · Apr 27, 2018 · 2464294 · 2464294
1 parent 38da55b
commit 2464294
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Showing 3 changed files with 6 additions and 2 deletions.
diff --git a/fasmg b/fasmg
diff --git a/fasmg.exe b/fasmg.exe
diff --git a/x86/Hash.asm b/x86/Hash.asm
@@ -34,15 +34,19 @@ MainHash_ReadOptions:
     @1:
     ; free current
            call  MainHash_Free
-           imul  rcx, rsi, 32
-    ; rcx = number of bytes in hash table
            test  ebx, 1
              jz  .NoLP
 .LP:
+           imul  rcx, rsi, 32    ; rcx = number of bytes in hash table
            call  Os_VirtualAlloc_LargePages
            test  rax, rax
             jnz  .Done
+           ; Note by Moha:
+           ;	Os_VirtualAlloc_LargePages
+           ;	obviously may clobber rcx			;
+           ;	so reload it before calling Os_VirtualAlloc
 .NoLP:
+           imul  rcx, rsi, 32    ; rcx = number of bytes in hash table
            call  Os_VirtualAlloc
             xor  edx, edx
 .Done: