UefiCpuPkg/MtrrLib: Optimize MtrrLibLeastAlignment()

The patch changes MtrrLibLeastAlignment() to
MtrrLibBiggestAlignment() and optimizes the implementation
to be more efficient.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

1 files changed, 13 insertions, 12 deletions

diff --git a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
index 5b21fe11f1..0fecc0122c 100644
--- a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
+++ b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
@@ -656,7 +656,8 @@ MtrrGetMemoryAttributeInVariableMtrr (
 }

 

 /**

-  Return the least alignment of address.

+  Return the biggest alignment (lowest set bit) of address.

+  The function is equivalent to: 1 << LowBitSet64 (Address).

 

   @param Address    The address to return the alignment.

   @param Alignment0 The alignment to return when Address is 0.

@@ -664,7 +665,7 @@ MtrrGetMemoryAttributeInVariableMtrr (
   @return The least alignment of the Address.

 **/

 UINT64

-MtrrLibLeastAlignment (

+MtrrLibBiggestAlignment (

   UINT64    Address,

   UINT64    Alignment0

 )

@@ -673,7 +674,7 @@ MtrrLibLeastAlignment (
     return Alignment0;

   }

 

-  return LShiftU64 (1, (UINTN) LowBitSet64 (Address));

+  return Address & ((~Address) + 1);

 }

 

 /**

@@ -705,12 +706,12 @@ MtrrLibGetPositiveMtrrNumber (
   //

   for (MtrrNumber = 0; Length != 0; MtrrNumber++) {

     if (UseLeastAlignment) {

-      SubLength = MtrrLibLeastAlignment (BaseAddress, Alignment0);

+      SubLength = MtrrLibBiggestAlignment (BaseAddress, Alignment0);

 

       if (SubLength > Length) {

         //

         // Set a flag when remaining length is too small

-        //  so that MtrrLibLeastAlignment() is not called in following loops.

+        //  so that MtrrLibBiggestAlignment() is not called in following loops.

         //

         UseLeastAlignment = FALSE;

       }

@@ -873,7 +874,7 @@ MtrrLibGetMtrrNumber (
     // Left subtraction bit by bit, to find the optimal left subtraction solution.

     //

     for (SubtractiveMtrrNumber = 0, SubtractiveCount = 1; BaseAddress != 0; SubtractiveCount++) {

-      Alignment = MtrrLibLeastAlignment (BaseAddress, Alignment0);

+      Alignment = MtrrLibBiggestAlignment (BaseAddress, Alignment0);

 

       //

       // Check whether the memory type of [BaseAddress - Alignment, BaseAddress) can override Type.

@@ -928,7 +929,7 @@ MtrrLibGetMtrrNumber (
   //

   MiddleMtrrNumber = 0;

   while (Length != 0) {

-    BaseAlignment = MtrrLibLeastAlignment (BaseAddress, Alignment0);

+    BaseAlignment = MtrrLibBiggestAlignment (BaseAddress, Alignment0);

     if (BaseAlignment > Length) {

       break;

     }

@@ -953,7 +954,7 @@ MtrrLibGetMtrrNumber (
   LeastRightMtrrNumber = MtrrLibGetPositiveMtrrNumber (BaseAddress, Length, Alignment0);

 

   for (SubtractiveCount = 1; Length < BaseAlignment; SubtractiveCount++) {

-    Alignment = MtrrLibLeastAlignment (BaseAddress + Length, Alignment0);

+    Alignment = MtrrLibBiggestAlignment (BaseAddress + Length, Alignment0);

     if (!MtrrLibSubstractable (Ranges, RangeCount, Type, BaseAddress + Length, Alignment)) {

       break;

     }

@@ -1644,7 +1645,7 @@ MtrrLibSetMemoryAttributeInVariableMtrr (
   }

 

   while (SubtractiveLeft-- != 0) {

-    Alignment = MtrrLibLeastAlignment (BaseAddress, Alignment0);

+    Alignment = MtrrLibBiggestAlignment (BaseAddress, Alignment0);

     ASSERT (Alignment <= Length);

 

     MtrrLibAddVariableMtrr (Ranges, RangeCount, VariableMtrr, VariableMtrrCapacity, VariableMtrrCount,

@@ -1654,7 +1655,7 @@ MtrrLibSetMemoryAttributeInVariableMtrr (
   }

 

   while (Length != 0) {

-    Alignment = MtrrLibLeastAlignment (BaseAddress, Alignment0);

+    Alignment = MtrrLibBiggestAlignment (BaseAddress, Alignment0);

     if (Alignment > Length) {

       break;

     }

@@ -1665,7 +1666,7 @@ MtrrLibSetMemoryAttributeInVariableMtrr (
   }

 

   while (SubtractiveRight-- != 0) {

-    Alignment = MtrrLibLeastAlignment (BaseAddress + Length, Alignment0);

+    Alignment = MtrrLibBiggestAlignment (BaseAddress + Length, Alignment0);

     MtrrLibAddVariableMtrr (Ranges, RangeCount, VariableMtrr, VariableMtrrCapacity, VariableMtrrCount,

                             BaseAddress + Length, Alignment, CacheInvalid, Alignment0);

     Length += Alignment;

@@ -1674,7 +1675,7 @@ MtrrLibSetMemoryAttributeInVariableMtrr (
   UseLeastAlignment = TRUE;

   while (Length != 0) {

     if (UseLeastAlignment) {

-      Alignment = MtrrLibLeastAlignment (BaseAddress, Alignment0);

+      Alignment = MtrrLibBiggestAlignment (BaseAddress, Alignment0);

       if (Alignment > Length) {

         UseLeastAlignment = FALSE;

       }