[llvm] r371136 - AMDGPU: Avoid constructing new std::vector in initCandidate

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Thu Sep  5 15:44:06 2019
New Revision: 371136

URL: http://llvm.org/viewvc/llvm-project?rev=371136&view=rev
Log:
AMDGPU: Avoid constructing new std::vector in initCandidate

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.

Modified:
    llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.cpp
    llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.h

Modified: llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.cpp?rev=371136&r1=371135&r2=371136&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.cpp (original)
+++ llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.cpp Thu Sep  5 15:44:06 2019
@@ -71,8 +71,8 @@ void GCNMaxOccupancySchedStrategy::initC
   // 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);

Modified: llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.h?rev=371136&r1=371135&r2=371136&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.h (original)
+++ llvm/trunk/lib/Target/AMDGPU/GCNSchedStrategy.h Thu Sep  5 15:44:06 2019
@@ -40,6 +40,9 @@ class GCNMaxOccupancySchedStrategy final
                      const SIRegisterInfo *SRI,
                      unsigned SGPRPressure, unsigned VGPRPressure);
 
+  std::vector<unsigned> Pressure;
+  std::vector<unsigned> MaxPressure;
+
   unsigned SGPRExcessLimit;
   unsigned VGPRExcessLimit;
   unsigned SGPRCriticalLimit;