[MCA][ResourceManager] Add a table that maps processor resource indices to processor resource identifiers.

This patch adds a lookup table to speed up resource queries in the ResourceManager.
This patch also moves helper function 'getResourceStateIndex()' from
ResourceManager.cpp to Support.h, so that we can reuse that logic in the
SummaryView (and potentially other views in llvm-mca).
No functional change intended.

llvm-svn: 354470

1 files changed, 24 insertions, 21 deletions

diff --git a/llvm/lib/MCA/HardwareUnits/ResourceManager.cpp b/llvm/lib/MCA/HardwareUnits/ResourceManager.cpp
index 21e0271c852..06f2476353d 100644
--- a/llvm/lib/MCA/HardwareUnits/ResourceManager.cpp
+++ b/llvm/lib/MCA/HardwareUnits/ResourceManager.cpp
@@ -23,16 +23,10 @@ namespace mca {
 #define DEBUG_TYPE "llvm-mca"
 ResourceStrategy::~ResourceStrategy() = default;
 
-// Returns the index of the highest bit set. For resource masks, the position of
-// the highest bit set can be used to construct a resource mask identifier.
-static unsigned getResourceStateIndex(uint64_t Mask) {
-  return std::numeric_limits<uint64_t>::digits - countLeadingZeros(Mask);
-}
-
 static uint64_t selectImpl(uint64_t CandidateMask,
                            uint64_t &NextInSequenceMask) {
   // The upper bit set in CandidateMask identifies our next candidate resource.
-  CandidateMask = 1ULL << (getResourceStateIndex(CandidateMask) - 1);
+  CandidateMask = 1ULL << getResourceStateIndex(CandidateMask);
   NextInSequenceMask &= (CandidateMask | (CandidateMask - 1));
   return CandidateMask;
 }
@@ -74,7 +68,7 @@ ResourceState::ResourceState(const MCProcResourceDesc &Desc, unsigned Index,
       BufferSize(Desc.BufferSize), IsAGroup(countPopulation(ResourceMask) > 1) {
   if (IsAGroup) {
     ResourceSizeMask =
-        ResourceMask ^ 1ULL << (getResourceStateIndex(ResourceMask) - 1);
+        ResourceMask ^ 1ULL << getResourceStateIndex(ResourceMask);
   } else {
     ResourceSizeMask = (1ULL << Desc.NumUnits) - 1;
   }
@@ -115,14 +109,21 @@ getStrategyFor(const ResourceState &RS) {
 }
 
 ResourceManager::ResourceManager(const MCSchedModel &SM)
-    : Resources(SM.getNumProcResourceKinds()),
-      Strategies(SM.getNumProcResourceKinds()),
-      Resource2Groups(SM.getNumProcResourceKinds(), 0),
-      ProcResID2Mask(SM.getNumProcResourceKinds()), ProcResUnitMask(0),
-      ReservedResourceGroups(0) {
+    : Resources(SM.getNumProcResourceKinds() - 1),
+      Strategies(SM.getNumProcResourceKinds() - 1),
+      Resource2Groups(SM.getNumProcResourceKinds() - 1, 0),
+      ProcResID2Mask(SM.getNumProcResourceKinds(), 0),
+      ResIndex2ProcResID(SM.getNumProcResourceKinds() - 1, 0),
+      ProcResUnitMask(0), ReservedResourceGroups(0) {
   computeProcResourceMasks(SM, ProcResID2Mask);
 
-  for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
+  // initialize vector ResIndex2ProcResID.
+  for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
+    unsigned Index = getResourceStateIndex(ProcResID2Mask[I]);
+    ResIndex2ProcResID[Index] = I;
+  }
+
+  for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
     uint64_t Mask = ProcResID2Mask[I];
     unsigned Index = getResourceStateIndex(Mask);
     Resources[Index] =
@@ -130,7 +131,7 @@ ResourceManager::ResourceManager(const MCSchedModel &SM)
     Strategies[Index] = getStrategyFor(*Resources[Index]);
   }
 
-  for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
+  for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
     uint64_t Mask = ProcResID2Mask[I];
     unsigned Index = getResourceStateIndex(Mask);
     const ResourceState &RS = *Resources[Index];
@@ -139,7 +140,7 @@ ResourceManager::ResourceManager(const MCSchedModel &SM)
       continue;
     }
 
-    uint64_t GroupMaskIdx = 1ULL << (Index - 1);
+    uint64_t GroupMaskIdx = 1ULL << Index;
     Mask -= GroupMaskIdx;
     while (Mask) {
       // Extract lowest set isolated bit.
@@ -162,7 +163,7 @@ void ResourceManager::setCustomStrategyImpl(std::unique_ptr<ResourceStrategy> S,
 }
 
 unsigned ResourceManager::resolveResourceMask(uint64_t Mask) const {
-  return Resources[getResourceStateIndex(Mask)]->getProcResourceID();
+  return ResIndex2ProcResID[getResourceStateIndex(Mask)];
 }
 
 unsigned ResourceManager::getNumUnits(uint64_t ResourceID) const {
@@ -332,18 +333,20 @@ void ResourceManager::cycleEvent(SmallVectorImpl<ResourceRef> &ResourcesFreed) {
 }
 
 void ResourceManager::reserveResource(uint64_t ResourceID) {
-  ResourceState &Resource = *Resources[getResourceStateIndex(ResourceID)];
+  const unsigned Index = getResourceStateIndex(ResourceID);
+  ResourceState &Resource = *Resources[Index];
   assert(Resource.isAResourceGroup() && !Resource.isReserved() &&
          "Unexpected resource found!");
   Resource.setReserved();
-  ReservedResourceGroups ^= PowerOf2Floor(ResourceID);
+  ReservedResourceGroups ^= 1ULL << Index;
 }
 
 void ResourceManager::releaseResource(uint64_t ResourceID) {
-  ResourceState &Resource = *Resources[getResourceStateIndex(ResourceID)];
+  const unsigned Index = getResourceStateIndex(ResourceID);
+  ResourceState &Resource = *Resources[Index];
   Resource.clearReserved();
   if (Resource.isAResourceGroup())
-    ReservedResourceGroups ^= PowerOf2Floor(ResourceID);
+    ReservedResourceGroups ^= 1ULL << Index;
 }
 
 } // namespace mca