Add BSF and BSR instruction wrappers

xtoskrnl/ar/amd64/cpufunc.cc

@@ -617,6 +617,56 @@ AR::CpuFunctions::ReadWriteBarrier(VOID)
                      : "memory");
 }
 
+/**
+ * Performs a Bit Scan Forward instruction to locate the most significant set bit.
+ *
+ * @param Index
+ *        Receives the zero-based index of the highest set bit when one is found.
+ *
+ * @param Mask
+ *        Supplies the bitmap to scan.
+ *
+ * @return This routine returns TRUE when a set bit was found, otherwise FALSE.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+BOOLEAN
+AR::CpuFunctions::ScanForwardBit(OUT PULONG Index,
+                                 IN ULONG Mask)
+{
+    /* Defer to the BSF instruction */
+    __asm__("bsfl %[Mask], %[Index]" : [Index] "=r" (*Index) : [Mask] "mr" (Mask));
+
+    /* Report whether the input had any bit set */
+    return Mask ? TRUE : FALSE;
+}
+
+/**
+ * Performs a Bit Scan Reverse instruction to locate the most significant set bit.
+ *
+ * @param Index
+ *        Receives the zero-based index of the highest set bit when one is found.
+ *
+ * @param Mask
+ *        Supplies the bitmap to scan.
+ *
+ * @return This routine returns TRUE when a set bit was found, otherwise FALSE.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+BOOLEAN
+AR::CpuFunctions::ScanReverseBit(OUT PULONG Index,
+                                 IN ULONG Mask)
+{
+    /* Defer to the BSR instruction */
+    __asm__("bsrl %[Mask], %[Index]" : [Index] "=r" (*Index) : [Mask] "mr" (Mask));
+
+    /* Report whether the input had any bit set */
+    return Mask ? TRUE : FALSE;
+}
+
 /**
  * Instructs the processor to set the interrupt flag.
  *

xtoskrnl/ar/i686/cpufunc.cc

@@ -587,6 +587,56 @@ AR::CpuFunctions::ReadWriteBarrier(VOID)
                      : "memory");
 }
 
+/**
+ * Performs a Bit Scan Forward instruction to locate the most significant set bit.
+ *
+ * @param Index
+ *        Receives the zero-based index of the highest set bit when one is found.
+ *
+ * @param Mask
+ *        Supplies the bitmap to scan.
+ *
+ * @return This routine returns TRUE when a set bit was found, otherwise FALSE.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+BOOLEAN
+AR::CpuFunctions::ScanForwardBit(OUT PULONG Index,
+                                 IN ULONG Mask)
+{
+    /* Defer to the BSF instruction */
+    __asm__("bsfl %[Mask], %[Index]" : [Index] "=r" (*Index) : [Mask] "mr" (Mask));
+
+    /* Report whether the input had any bit set */
+    return Mask ? TRUE : FALSE;
+}
+
+/**
+ * Performs a Bit Scan Reverse instruction to locate the most significant set bit.
+ *
+ * @param Index
+ *        Receives the zero-based index of the highest set bit when one is found.
+ *
+ * @param Mask
+ *        Supplies the bitmap to scan.
+ *
+ * @return This routine returns TRUE when a set bit was found, otherwise FALSE.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+BOOLEAN
+AR::CpuFunctions::ScanReverseBit(OUT PULONG Index,
+                                 IN ULONG Mask)
+{
+    /* Defer to the BSR instruction */
+    __asm__("bsrl %[Mask], %[Index]" : [Index] "=r" (*Index) : [Mask] "mr" (Mask));
+
+    /* Report whether the input had any bit set */
+    return Mask ? TRUE : FALSE;
+}
+
 /**
  * Instructs the processor to set the interrupt flag.
  *

xtoskrnl/includes/ar/amd64/cpufunc.hh

@@ -42,6 +42,10 @@ namespace AR
             STATIC XTCDECL ULONGLONG ReadTimeStampCounter(VOID);
             STATIC XTCDECL ULONGLONG ReadTimeStampCounterProcessor(OUT PULONG TscAux);
             STATIC XTCDECL VOID ReadWriteBarrier(VOID);
+            STATIC XTCDECL BOOLEAN ScanForwardBit(OUT PULONG Index,
+                                                  IN ULONG Mask);
+            STATIC XTCDECL BOOLEAN ScanReverseBit(OUT PULONG Index,
+                                                  IN ULONG Mask);
             STATIC XTCDECL VOID SetInterruptFlag(VOID);
             STATIC XTCDECL VOID StoreGlobalDescriptorTable(OUT PVOID Destination);
             STATIC XTCDECL VOID StoreInterruptDescriptorTable(OUT PVOID Destination);

xtoskrnl/includes/ar/i686/cpufunc.hh

@@ -41,6 +41,10 @@ namespace AR
             STATIC XTCDECL ULONGLONG ReadTimeStampCounter(VOID);
             STATIC XTCDECL ULONGLONG ReadTimeStampCounterProcessor(OUT PULONG TscAux);
             STATIC XTCDECL VOID ReadWriteBarrier(VOID);
+            STATIC XTCDECL BOOLEAN ScanForwardBit(OUT PULONG Index,
+                                                  IN ULONG Mask);
+            STATIC XTCDECL BOOLEAN ScanReverseBit(OUT PULONG Index,
+                                                  IN ULONG Mask);
             STATIC XTCDECL VOID SetInterruptFlag(VOID);
             STATIC XTCDECL VOID StoreGlobalDescriptorTable(OUT PVOID Destination);
             STATIC XTCDECL VOID StoreInterruptDescriptorTable(OUT PVOID Destination);