From 5a5ac124e1efaf208671f01c46edb15f29ed2a0b Mon Sep 17 00:00:00 2001
From: Dimitry Andric <dim@FreeBSD.org>
Date: Wed, 27 May 2015 18:44:32 +0000
Subject: Vendor import of llvm trunk r238337:
 https://llvm.org/svn/llvm-project/llvm/trunk@238337

---
 lib/CodeGen/RegisterPressure.cpp | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

(limited to 'lib/CodeGen/RegisterPressure.cpp')

diff --git a/lib/CodeGen/RegisterPressure.cpp b/lib/CodeGen/RegisterPressure.cpp
index 9925efbff24b..667783e29526 100644
--- a/lib/CodeGen/RegisterPressure.cpp
+++ b/lib/CodeGen/RegisterPressure.cpp
@@ -304,6 +304,7 @@ static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
   return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
 }
 
+namespace {
 /// Collect this instruction's unique uses and defs into SmallVectors for
 /// processing defs and uses in order.
 ///
@@ -354,6 +355,7 @@ protected:
     }
   }
 };
+} // namespace
 
 /// Collect physical and virtual register operands.
 static void collectOperands(const MachineInstr *MI,
@@ -748,9 +750,11 @@ void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
 ///
 /// This assumes that the current LiveOut set is sufficient.
 ///
-/// FIXME: This is expensive for an on-the-fly query. We need to cache the
-/// result per-SUnit with enough information to adjust for the current
-/// scheduling position. But this works as a proof of concept.
+/// This is expensive for an on-the-fly query because it calls
+/// bumpUpwardPressure to recompute the pressure sets based on current
+/// liveness. This mainly exists to verify correctness, e.g. with
+/// -verify-misched. getUpwardPressureDelta is the fast version of this query
+/// that uses the per-SUnit cache of the PressureDiff.
 void RegPressureTracker::
 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
                           RegPressureDelta &Delta,
@@ -807,10 +811,8 @@ getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
 #endif
 }
 
-/// This is a prototype of the fast version of querying register pressure that
-/// does not directly depend on current liveness. It's still slow because we
-/// recompute pressure change on-the-fly. This implementation only exists to
-/// prove correctness.
+/// This is the fast version of querying register pressure that does not
+/// directly depend on current liveness.
 ///
 /// @param Delta captures information needed for heuristics.
 ///
@@ -948,6 +950,11 @@ void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
 /// register units of that pressure set introduced by this instruction.
 ///
 /// This assumes that the current LiveIn set is sufficient.
+///
+/// This is expensive for an on-the-fly query because it calls
+/// bumpDownwardPressure to recompute the pressure sets based on current
+/// liveness. We don't yet have a fast version of downward pressure tracking
+/// analagous to getUpwardPressureDelta.
 void RegPressureTracker::
 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
                             ArrayRef<PressureChange> CriticalPSets,
-- 
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