Re: [PATCH] MdePkg/BaseLib: Add bit field Hamming weight calculation methods

["Gao, Liming" <liming.gao@intel.com>]

Tomas:
  Could you share some background what code depends on new added APIs? 

Thanks
Liming
>-----Original Message-----
>From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
>Tomas Pilar (tpilar)
>Sent: Friday, June 29, 2018 5:42 PM
>To: edk2-devel@lists.01.org
>Subject: [edk2] [PATCH] MdePkg/BaseLib: Add bit field Hamming weight
>calculation methods
>
>Add 32-bit and 64-bit functions that count number of set bits in a bitfield
>using the divide-and-count method.
>
>Contributed-under: TianoCore Contribution Agreement 1.1
>Signed-off-by: Tomas Pilar <tpilar@solarflare.com>
>---
> MdePkg/Include/Library/BaseLib.h  | 56 +++++++++++++++++++++++++++
> MdePkg/Library/BaseLib/BitField.c | 79
>+++++++++++++++++++++++++++++++++++++++
> 2 files changed, 135 insertions(+)
>
>diff --git a/MdePkg/Include/Library/BaseLib.h
>b/MdePkg/Include/Library/BaseLib.h
>index 1db3a04..7eb0488 100644
>--- a/MdePkg/Include/Library/BaseLib.h
>+++ b/MdePkg/Include/Library/BaseLib.h
>@@ -4609,6 +4609,62 @@ BitFieldAndThenOr64 (
>   IN      UINT64                    OrData
>   );
>
>+/**
>+  Reads a bit field from a 32-bit value, counts and returns
>+  the number of set bits.
>+
>+  Counts the number of set bits in the  bit field specified by
>+  StartBit and EndBit in Operand. The count is returned.
>+
>+  If StartBit is greater than 31, then ASSERT().
>+  If EndBit is greater than 31, then ASSERT().
>+  If EndBit is less than StartBit, then ASSERT().
>+
>+  @param  Operand   Operand on which to perform the bitfield operation.
>+  @param  StartBit  The ordinal of the least significant bit in the bit field.
>+                    Range 0..31.
>+  @param  EndBit    The ordinal of the most significant bit in the bit field.
>+                    Range 0..31.
>+
>+  @return The number of bits set between StartBit and EndBit.
>+
>+**/
>+UINT8
>+EFIAPI
>+BitFieldHammingWeight32 (
>+  IN       UINT32                   Operand,
>+  IN       UINTN                    StartBit,
>+  IN       UINTN                    EndBit
>+  );
>+
>+/**
>+   Reads a bit field from a 64-bit value, counts and returns
>+   the number of set bits.
>+
>+   Counts the number of set bits in the  bit field specified by
>+   StartBit and EndBit in Operand. The count is returned.
>+
>+   If StartBit is greater than 63, then ASSERT().
>+   If EndBit is greater than 63, then ASSERT().
>+   If EndBit is less than StartBit, then ASSERT().
>+
>+   @param  Operand   Operand on which to perform the bitfield operation.
>+   @param  StartBit  The ordinal of the least significant bit in the bit field.
>+   Range 0..63.
>+   @param  EndBit    The ordinal of the most significant bit in the bit field.
>+   Range 0..63.
>+
>+   @return The number of bits set between StartBit and EndBit.
>+
>+**/
>+UINT8
>+EFIAPI
>+BitFieldHammingWeight64 (
>+  IN       UINT64                   Operand,
>+  IN       UINTN                    StartBit,
>+  IN       UINTN                    EndBit
>+  );
>+
> //
> // Base Library Checksum Functions
> //
>diff --git a/MdePkg/Library/BaseLib/BitField.c
>b/MdePkg/Library/BaseLib/BitField.c
>index d2d3150..af06db8 100644
>--- a/MdePkg/Library/BaseLib/BitField.c
>+++ b/MdePkg/Library/BaseLib/BitField.c
>@@ -920,3 +920,82 @@ BitFieldAndThenOr64 (
>            OrData
>            );
> }
>+
>+/**
>+  Reads a bit field from a 32-bit value, counts and returns
>+  the number of set bits.
>+
>+  Counts the number of set bits in the  bit field specified by
>+  StartBit and EndBit in Operand. The count is returned.
>+
>+  If StartBit is greater than 31, then ASSERT().
>+  If EndBit is greater than 31, then ASSERT().
>+  If EndBit is less than StartBit, then ASSERT().
>+
>+  @param  Operand   Operand on which to perform the bitfield operation.
>+  @param  StartBit  The ordinal of the least significant bit in the bit field.
>+                    Range 0..31.
>+  @param  EndBit    The ordinal of the most significant bit in the bit field.
>+                    Range 0..31.
>+
>+  @return The number of bits set between StartBit and EndBit.
>+
>+**/
>+UINT8
>+EFIAPI
>+BitFieldHammingWeight32 (
>+  IN       UINT32                   Operand,
>+  IN       UINTN                    StartBit,
>+  IN       UINTN                    EndBit
>+  )
>+{
>+  ASSERT (EndBit < 32);
>+  ASSERT (StartBit <= EndBit);
>+
>+  UINT32 Count = BitFieldRead32 (Operand, StartBit, EndBit);
>+  Count -= ((Count >> 1) & 0x55555555);
>+  Count = (Count & 0x33333333) + ((Count >> 2) & 0x33333333);
>+  Count += Count >> 4;
>+  Count &= 0x0F0F0F0F;
>+  Count += Count >> 8;
>+  Count += Count >> 16;
>+
>+  return (UINT8) Count & 0x3F;
>+}
>+
>+/**
>+   Reads a bit field from a 64-bit value, counts and returns
>+   the number of set bits.
>+
>+   Counts the number of set bits in the  bit field specified by
>+   StartBit and EndBit in Operand. The count is returned.
>+
>+   If StartBit is greater than 63, then ASSERT().
>+   If EndBit is greater than 63, then ASSERT().
>+   If EndBit is less than StartBit, then ASSERT().
>+
>+   @param  Operand   Operand on which to perform the bitfield operation.
>+   @param  StartBit  The ordinal of the least significant bit in the bit field.
>+   Range 0..63.
>+   @param  EndBit    The ordinal of the most significant bit in the bit field.
>+   Range 0..63.
>+
>+   @return The number of bits set between StartBit and EndBit.
>+
>+**/
>+UINT8
>+EFIAPI
>+BitFieldHammingWeight64 (
>+  IN       UINT64                   Operand,
>+  IN       UINTN                    StartBit,
>+  IN       UINTN                    EndBit
>+  )
>+{
>+  ASSERT (EndBit < 64);
>+  ASSERT (StartBit <= EndBit);
>+
>+  UINT64 BitField = BitFieldRead64 (Operand, StartBit, EndBit);
>+  UINT8 Count = BitFieldHammingWeight32 (BitField, 0, 31);
>+  return Count + BitFieldHammingWeight32(RShiftU64(BitField, 32), 0, 31);
>+}
>+
>--
>2.9.5
>
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