Correct register pressure calculation in presence of subregs

If a subreg is used in an instruction it counts as a whole superreg
for the purpose of register pressure calculation. This patch corrects
improper register pressure calculation by examining operand's lane mask.

Differential Revision: https://reviews.llvm.org/D29835

llvm-svn: 296009

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
index 39324cbbcc0..f1d037d1159 100644
--- a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -21,6 +21,7 @@
 #include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/Support/MathExtras.h"
 
 using namespace llvm;
 
@@ -1408,3 +1409,18 @@ const int *SIRegisterInfo::getRegUnitPressureSets(unsigned RegUnit) const {
     return Empty;
   return AMDGPURegisterInfo::getRegUnitPressureSets(RegUnit);
 }
+
+unsigned SIRegisterInfo::getRegUnitWeight(const MachineRegisterInfo &MRI,
+                                          unsigned RegUnit,
+                                          LaneBitmask LaneMask) const {
+  unsigned Weight = TargetRegisterInfo::getRegUnitWeight(MRI, RegUnit,
+                                                         LaneMask);
+  if (Weight > 1 && LaneMask.any() && !LaneMask.all() &&
+      isVirtualRegister(RegUnit)) {
+    LaneBitmask Max = MRI.getMaxLaneMaskForVReg(RegUnit);
+    if (Max != LaneMask && !Max.all() && !Max.none())
+      Weight = (Weight * countPopulation(LaneMask.getAsInteger())) /
+                         countPopulation(Max.getAsInteger());
+  }
+  return Weight;
+}