BCR tuning

BCR tuning

Author: bcheng0127

visa/G4_Kernel.cpp

@@ -618,6 +618,12 @@ void G4_Kernel::calculateSimdSize() {
     computeChannelSlicing();
 }
 
+bool G4_Kernel::reachMaxGRF() {
+  if (numRegTotal >= grfMode.getMaxGRF())
+    return true;
+  return false;
+}
+
 //
 // Updates kernel's related structures to large GRF
 //

visa/G4_Kernel.hpp

@@ -691,6 +691,7 @@ class G4_Kernel {
   void setName(const char *n) { name = n; }
   const char *getName() const { return name; }
 
+  bool reachMaxGRF();
   bool updateKernelToLargerGRF();
   void updateKernelByRegPressure(unsigned regPressure);
   bool updateKernelFromNumGRFAttr();

visa/GraphColor.cpp

@@ -1022,7 +1022,7 @@ void BankConflictPass::setupBankConflictsForBBTGL(G4_BB *bb,
       } else {
         setupBankConflictsforMad(inst);
       }
-    } else if (gra.kernel.getOption(vISA_forceBCR) && !forGlobal &&
+    } else if (gra.forceBCR && !forGlobal &&
                inst->getNumSrc() == 2) {
       threeSourceInstNum++;
       setupBankConflictsforMad(inst);
@@ -3499,7 +3499,7 @@ bool Augmentation::markNonDefaultMaskDef() {
         nonDefaultMaskDefFound = true;
       }
 
-      if (kernel.getOption(vISA_forceBCR) &&
+      if ((gra.favorBCR || gra.forceBCR) &&
           gra.getBankConflict(dcl) != BANK_CONFLICT_NONE) {
         gra.setAugmentationMask(dcl, AugmentationMasks::NonDefault);
         nonDefaultMaskDefFound = true;
@@ -6723,7 +6723,7 @@ bool GraphColor::assignColors(ColorHeuristic colorHeuristicGRF,
         // pass) then abort on spill
         //
         if ((heuristic == ROUND_ROBIN ||
-             (doBankConflict && !kernel.getOption(vISA_forceBCR))) &&
+             (doBankConflict && !gra.forceBCR)) &&
             (lr->getRegKind() == G4_GRF || lr->getRegKind() == G4_FLAG)) {
           return false;
         } else if (kernel.fg.isPseudoDcl(dcl)) {
@@ -7345,11 +7345,9 @@ bool GraphColor::regAlloc(bool doBankConflictReduction,
           return false;
         }
 
-        if (!kernel.getOption(vISA_forceBCR)) {
-          if (!success && doBankConflictReduction) {
-            resetTemporaryRegisterAssignments();
-            assignColors(FIRST_FIT);
-          }
+        if (!success && doBankConflictReduction && !gra.forceBCR) {
+          resetTemporaryRegisterAssignments();
+          assignColors(FIRST_FIT);
         }
       }
     } else {
@@ -10111,6 +10109,16 @@ bool GlobalRA::tryHybridRA() {
     return true;
   }
 
+  //Skip hybridRA if BCR is needed
+  if (favorBCR) {
+    lra.undoLocalRAAssignments(true);
+    // Restore alignment in case LRA modified it
+    copyAlignment();
+    //reset favorBCR
+    favorBCR = false;
+    return false;
+  }
+
   if (useHybridRAwithSpill) {
     insertPhyRegDecls();
   } else {
@@ -10431,14 +10439,14 @@ std::pair<bool, bool> GlobalRA::bankConflict() {
   bool doBankConflictReduction = false, highInternalConflict = false;
   if (builder.getOption(vISA_LocalBankConflictReduction) &&
       builder.hasBankCollision()) {
-    bool reduceBCInRR = false;
-    bool reduceBCInTAandFF = false;
+    bool reduceBC = false;
+    bool threeSouceBCR = false;
     BankConflictPass bc(*this, true);
 
-    reduceBCInRR = bc.setupBankConflictsForKernel(
-        true, reduceBCInTAandFF, SECOND_HALF_BANK_START_GRF * 2,
+    reduceBC = bc.setupBankConflictsForKernel(
+        true, threeSouceBCR, SECOND_HALF_BANK_START_GRF * 2,
         highInternalConflict);
-    doBankConflictReduction = reduceBCInRR && reduceBCInTAandFF;
+    doBankConflictReduction = reduceBC && threeSouceBCR;
   }
   return std::make_pair(doBankConflictReduction, highInternalConflict);
 }
@@ -10769,11 +10777,8 @@ GlobalRA::insertSpillCode(bool enableSpillSpaceCompression,
 
 bool GlobalRA::rerunGRAIter(bool rerunGRA)
 {
-  if (getIterNo() == 0 && (rerunGRA || kernel.getOption(vISA_forceBCR))) {
-    if (kernel.getOption(vISA_forceBCR)) {
-      // FIXME: We shouldn't modify options. Use local bool flag instead.
-      kernel.getOptions()->setOption(vISA_forceBCR, false);
-    }
+  if (getIterNo() == 0 && (rerunGRA || forceBCR)) {
+    forceBCR = false;
     return true;
   }
   return false;
@@ -10991,6 +10996,15 @@ int GlobalRA::coloringRegAlloc() {
     if (!fastCompile) {
       rpe.run();
       writeVerboseRPEStats(rpe);
+
+      // If the register pressure is less than TotalGRF - 16, mostly the
+      // BCR register allocation will success. In this case we do favor BCR
+      // register allocation in augmentation and assignColors and VRT GRF
+      // increasing
+      favorBCR |= doBankConflictReduction && kernel.useAutoGRFSelection() &&
+                  builder.favorBCR() && kernel.getOption(vISA_RoundRobin) &&
+                  !hasStackCall &&
+                  (rpe.getMaxRP() < kernel.getNumRegTotal() - 16);
     }
     GraphColor coloring(liveAnalysis, false, forceSpill);
 

visa/GraphColor.h

@@ -1485,6 +1485,8 @@ class GlobalRA {
   bool useFastRA = false;
   bool useHybridRAwithSpill = false;
   bool useLocalRA = false;
+  bool favorBCR = false;
+  bool forceBCR = false;
   uint32_t nextSpillOffset = 0;
   uint32_t scratchOffset = 0;
 
@@ -1918,7 +1920,7 @@ class GlobalRA {
     if (kernel.getOptions()->getOption(vISA_VerifyAugmentation)) {
       verifyAugmentation = std::make_unique<VerifyAugmentation>();
     }
-
+    forceBCR = kernel.getOption(vISA_forceBCR);
     // Set callWA condition.
     //    Call return ip and mask need wa only for non-entry functions. As call
     //    WA also needs a temp, we conservatively add WA for

visa/HWCaps.inc

@@ -881,4 +881,8 @@ bool hasMulMacRSIssue() const {
 
   return VISA_WA_CHECK(getPWaTable(), Wa_18035690555);
 }
+
+bool favorBCR() {
+  return false;
+}
 // end HW capabilities

visa/LocalRA.cpp

@@ -428,7 +428,7 @@ bool LocalRA::localRA() {
   }
 
   if (!doRoundRobin) {
-    if (kernel.getOption(vISA_forceBCR) && doBCR) {
+    if (gra.forceBCR && doBCR) {
       RA_TRACE(std::cout << "\t--first-fit BCR RA\n");
       needGlobalRA = localRAPass(false, doSplitLLR);
     }
@@ -444,6 +444,10 @@ bool LocalRA::localRA() {
       specialAlign();
       needGlobalRA = localRAPass(false, doSplitLLR);
     }
+    gra.favorBCR |= doBCR && kernel.useAutoGRFSelection() &&
+                    builder.favorBCR() && kernel.getOption(vISA_RoundRobin) &&
+                    !kernel.fg.getHasStackCalls() &&
+                    !kernel.fg.getIsStackCallFunc();
   }
 
   if (needGlobalRA == false) {