[BOOTSECT] FAT bootsectors: Use movzx in judicious places

Author: HBelusca

boot/freeldr/bootsect/fat.S

@@ -149,9 +149,8 @@ CalcDriveSize:
 
 
     // Now we must find our way to the first sector of the root directory
-    xor ax, ax
     xor cx, cx
-    mov al, byte ptr BP_REL(NumberOfFats)       // Number of fats
+    movzx ax, byte ptr BP_REL(NumberOfFats)     // Number of fats
     mul word ptr BP_REL(SectorsPerFat)          // Times sectors per fat
     add ax, word ptr BP_REL(HiddenSectors)
     adc dx, word ptr BP_REL(HiddenSectors+2)    // Add the number of hidden sectors
@@ -271,18 +270,16 @@ ReadCluster:
     // StartSector = ((Cluster - 2) * SectorsPerCluster) + ReservedSectors + HiddenSectors;
     dec ax                              // Adjust start cluster by 2
     dec ax                              // Because the data area starts on cluster 2
-    xor ch, ch
-    mov cl, byte ptr BP_REL(SectsPerCluster)
+    movzx cx, byte ptr BP_REL(SectsPerCluster)
     mul cx                              // Times sectors per cluster
     add ax, [bp-DataAreaStartLow]       // Add start of data area
     adc dx, [bp-DataAreaStartHigh]      // Now we have DX:AX with the logical start sector of FREELDR.SYS
     xor bx, bx                          // We will load it to [ES:0000], ES loaded before function call
-//  mov  cl,BYTE [BYTE bp+SectsPerCluster]// Sectors per cluster still in CX
+//  movzx cx, byte ptr BP_REL(SectsPerCluster) // Sectors per cluster still in CX
 //  call ReadSectors
 //  ret
 
 
-
 // Reads logical sectors into [ES:BX]
 // DX:AX has logical sector number to read
 // CX has number of sectors to read

boot/freeldr/bootsect/fat32.S

@@ -341,8 +341,7 @@ ContinueSearch:
 
     // Now we have to find our way through the root directory to
     // The FREELDR.SYS file
-    xor  bx,bx
-    mov  bl, byte ptr BP_REL(SectsPerCluster)
+    movzx bx, byte ptr BP_REL(SectsPerCluster)
     shl  bx, 4              // BX = BX * 512 / 32
     mov  ax, HEX(2000)      // We loaded at 2000:0000
     mov  es, ax
@@ -406,8 +405,7 @@ LoadFile:
     call ReadCluster
     pop  es
 
-    xor  bx, bx
-    mov  bl, byte ptr BP_REL(SectsPerCluster)
+    movzx bx, byte ptr BP_REL(SectsPerCluster)
     shl  bx, 5                  // BX = BX * 512 / 16
     mov  ax, es                 // Increment the load address by
     add  ax, bx                 // The size of a cluster
@@ -495,7 +493,6 @@ FatSectorInCache:                               // This variable tells us which
 // Reads cluster number in EAX into [ES:0000]
 ReadCluster:
     // StartSector = ((Cluster - 2) * SectorsPerCluster) + ReservedSectors + HiddenSectors;
-
     dec   eax
     dec   eax
     xor   edx, edx

boot/freeldr/bootsect/pc98/fat12fdd.S

@@ -161,9 +161,8 @@ VideoTestDone:
      *
      * LBA = NumberOfFats * SectorsPerFat + HiddenSectors + ReservedSectors
      */
-    xor ax, ax
     xor cx, cx
-    mov al, byte ptr BP_REL(NumberOfFats)       // Number of fats
+    movzx ax, byte ptr BP_REL(NumberOfFats)     // Number of fats
     mul word ptr BP_REL(SectorsPerFat)          // Times sectors per fat
     add ax, word ptr BP_REL(HiddenSectors)
     adc dx, word ptr BP_REL(HiddenSectors + 2)  // Add the number of hidden sectors
@@ -272,8 +271,7 @@ ReadCluster:
      */
     dec ax                                      // Adjust start cluster by 2
     dec ax                                      // Because the data area starts on cluster 2
-    xor ch, ch
-    mov cl, byte ptr BP_REL(SectsPerCluster)
+    movzx cx, byte ptr BP_REL(SectsPerCluster)
     mul cx                                      // Times sectors per cluster
     add ax, [bp - DataAreaStartLow]             // Add start of data area
     adc dx, [bp - DataAreaStartHigh]            // Now we have DX:AX with the logical start sector of FREELDR.SYS