Index: lib/Target/AMDGPU/GCNRegPressure.cpp
===================================================================
--- lib/Target/AMDGPU/GCNRegPressure.cpp
+++ lib/Target/AMDGPU/GCNRegPressure.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "GCNRegPressure.h"
+#include "llvm/CodeGen/RegisterPressure.h"
 
 using namespace llvm;
 
@@ -264,6 +265,61 @@
   MaxPressure = CurPressure = getRegPressure(*MRI, LiveRegs);
 }
 
+struct MachineInstrRegs {
+  SmallVector<RegisterMaskPair, 4> Defs;
+  SmallVector<RegisterMaskPair, 8> Uses;
+
+private:
+  static RegisterMaskPair& insert(SmallVectorImpl<RegisterMaskPair> &A,
+                                  unsigned Reg) {
+    auto I = std::find_if(A.begin(), A.end(), [Reg](const RegisterMaskPair &RM) {
+      return RM.RegUnit == Reg;
+    });
+    if (I != A.end())
+      return *I;
+    A.push_back(RegisterMaskPair(Reg, LaneBitmask::getNone()));
+    return A.back();
+  }
+
+public:
+  static MachineInstrRegs collectVirtualRegs(const MachineInstr &MI,
+                                             const LiveIntervals &LIS,
+                                             const MachineRegisterInfo &MRI) {
+    MachineInstrRegs Res;
+    for (const auto &MO : MI.operands()) {
+      if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
+        continue;
+
+      if (MO.isDef() && !MO.isDead()) {
+        auto &LaneMask = insert(Res.Defs, MO.getReg()).LaneMask;
+        LaneMask |= MO.getSubReg() == 0 ?
+          MRI.getMaxLaneMaskForVReg(MO.getReg()) :
+          MRI.getTargetRegisterInfo()->getSubRegIndexLaneMask(MO.getSubReg());
+      } else
+      if (MO.isUse() && MO.readsReg()) {
+        auto &LaneMask = insert(Res.Uses, MO.getReg()).LaneMask;
+        auto const MaxMask = MRI.getMaxLaneMaskForVReg(MO.getReg());
+        if (MaxMask.getAsInteger() == 1) // cannot have subregs
+          LaneMask = MaxMask;
+        else if (auto SubReg = MO.getSubReg())
+          LaneMask |= MRI.getTargetRegisterInfo()->getSubRegIndexLaneMask(SubReg);
+        else
+          LaneMask = LaneBitmask::getAll(); // check actual usage mask later (once)
+      }
+    }
+    // adjust correct usage mask using LIS
+    for (auto &U : Res.Uses) {
+      if (!U.LaneMask.all()) continue;
+      // For a tentative schedule LIS isn't updated yet but livemask should remain
+      // the same on any schedule. Subreg defs can be reordered but they all must
+      // dominate uses anyway.
+      auto SI = LIS.getInstructionIndex(MI).getBaseIndex();
+      U.LaneMask = getLiveLaneMask(U.RegUnit, SI, LIS, MRI);
+    }
+    return Res;
+  }
+};
+
 void GCNUpwardRPTracker::recede(const MachineInstr &MI) {
   assert(MRI && "call reset first");
 
@@ -272,34 +328,30 @@
   if (MI.isDebugValue())
     return;
 
-  // process all defs first to ensure early clobbers are handled correctly
-  // iterating over operands() to catch implicit defs
-  for (const auto &MO : MI.operands()) {
-    if (!MO.isReg() || !MO.isDef() ||
-      !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
-      continue;
+  auto const Regs = MachineInstrRegs::collectVirtualRegs(MI, LIS, *MRI);
 
-    auto Reg = MO.getReg();
-    auto &LiveMask = LiveRegs[Reg];
-    auto PrevMask = LiveMask;
-    LiveMask &= ~getDefRegMask(MO);
-    CurPressure.inc(Reg, PrevMask, LiveMask, *MRI);
+  // calc pressure at the MI (defs + uses)
+  auto AtMIPressure = CurPressure;
+  for (const auto &U : Regs.Uses) {
+    auto LiveMask = LiveRegs[U.RegUnit];
+    AtMIPressure.inc(U.RegUnit, LiveMask, LiveMask | U.LaneMask, *MRI);
   }
+  // update max pressure
+  MaxPressure = max(AtMIPressure, MaxPressure);
 
-  // then all uses
-  for (const auto &MO : MI.uses()) {
-    if (!MO.isReg() || !MO.readsReg() ||
-      !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
-      continue;
-
-    auto Reg = MO.getReg();
-    auto &LiveMask = LiveRegs[Reg];
+  for (const auto &D : Regs.Defs) {
+    auto &LiveMask = LiveRegs[D.RegUnit];
     auto PrevMask = LiveMask;
-    LiveMask |= getUsedRegMask(MO);
-    CurPressure.inc(Reg, PrevMask, LiveMask, *MRI);
+    LiveMask &= ~D.LaneMask;
+    CurPressure.inc(D.RegUnit, PrevMask, LiveMask, *MRI);
   }
-
-  MaxPressure = max(MaxPressure, CurPressure);
+  for (const auto &U : Regs.Uses) {
+    auto &LiveMask = LiveRegs[U.RegUnit];
+    auto PrevMask = LiveMask;
+    LiveMask |= U.LaneMask;
+    CurPressure.inc(U.RegUnit, PrevMask, LiveMask, *MRI);
+  }
+  assert(CurPressure == getRegPressure(*MRI, LiveRegs));
 }
 
 bool GCNDownwardRPTracker::reset(const MachineInstr &MI,