[PATCH] D67242: AMDGPU: Avoid constructing new std::vector in initCandidate

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: vpykhtin, rampitec.
Herald added subscribers: t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl.

Approximately 30% of the time was spent in the std::vector
constructor. In one testcase this pushes the scheduler to being the
second slowest pass.

      

I'm not sure I understand why these vector are necessary. The default
scheduler initCandidate seems to use some pre-existing vectors for the
pressure.


https://reviews.llvm.org/D67242

Files:
  lib/Target/AMDGPU/GCNSchedStrategy.cpp
  lib/Target/AMDGPU/GCNSchedStrategy.h


Index: lib/Target/AMDGPU/GCNSchedStrategy.h
===================================================================
--- lib/Target/AMDGPU/GCNSchedStrategy.h
+++ lib/Target/AMDGPU/GCNSchedStrategy.h
@@ -40,6 +40,9 @@
                      const SIRegisterInfo *SRI,
                      unsigned SGPRPressure, unsigned VGPRPressure);
 
+  std::vector<unsigned> Pressure;
+  std::vector<unsigned> MaxPressure;
+
   unsigned SGPRExcessLimit;
   unsigned VGPRExcessLimit;
   unsigned SGPRCriticalLimit;
Index: lib/Target/AMDGPU/GCNSchedStrategy.cpp
===================================================================
--- lib/Target/AMDGPU/GCNSchedStrategy.cpp
+++ lib/Target/AMDGPU/GCNSchedStrategy.cpp
@@ -71,8 +71,8 @@
   // the tracker, so we need to pass those function a non-const copy.
   RegPressureTracker &TempTracker = const_cast<RegPressureTracker&>(RPTracker);
 
-  std::vector<unsigned> Pressure;
-  std::vector<unsigned> MaxPressure;
+  Pressure.clear();
+  MaxPressure.clear();
 
   if (AtTop)
     TempTracker.getDownwardPressure(SU->getInstr(), Pressure, MaxPressure);


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