small improvements in asm function

Author: hg747

entries/hgrosser/README.md

@@ -3,7 +3,7 @@
 **1 billion row Challenge entry**
 
 ## Version
-Version 1.50
+Version 1.51
 
 ## How to compile
 The program was developed with FPC 3.2.2 and Lazarus 2.2.4
@@ -36,3 +36,4 @@ To speed things up:
 
 - Version 1.00: initial version
 - Version 1.50: hash-list optimized, small improvements in parsing the file
+- Version 1.51: small improvements in asm function

entries/hgrosser/src/1brc.pas

@@ -20,7 +20,7 @@
      sysutils, strutils, math;
 
 const
-  M_version = '1.50'; {version number}
+  M_version = '1.51'; {version number}
 
 {------------------------------ Common routines: ------------------------------}
 
@@ -106,23 +106,20 @@ procedure error_halt(s: ansistring);
 {$ASMMODE INTEL}
 
 function FPHashX_ASM(var buf; len: dword): dword; assembler; nostackframe;
-   {returns a hash code similar to function FPHash() from FPC-Unit 'Contnrs',
-    but with the difference, that all hash codes for all cities here are UNIQUE.
-    I: len: MUST BE > 0!}
-// var buf = RDI
-// var len = ESI
+  {returns a hash code similar to function FPHash() from FPC-Unit 'Contnrs',
+   but with the difference, that all hash codes for all cities here are UNIQUE.
+   I: len: MUST BE > 0!}
 asm
-         MOV     ECX,len
          MOV     EAX,dword(-1)
 
          @LOOP:
          MOV     EDX,EAX       // save Result
          SHL     EAX,5         // eax := Result shl 5
          SUB     EAX,EDX       // eax := Result shl 5 - Result
 
-         XOR     AL, [RDI]
-         INC     RDI
-         DEC     ECX
+         XOR     AL, [buf]
+         INC     buf
+         DEC     len
          JNZ     @LOOP
 end; {FPHashX_ASM}