Prefer cheap registers for busy live ranges.
On the x86-64 and thumb2 targets, some registers are more expensive to encode
than others in the same register class.
Add a CostPerUse field to the TableGen register description, and make it
available from TRI->getCostPerUse. This represents the cost of a REX prefix or a
32-bit instruction encoding required by choosing a high register.
Teach the greedy register allocator to prefer cheap registers for busy live
ranges (as indicated by spill weight).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129864 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocBasic.cpp b/lib/CodeGen/RegAllocBasic.cpp
index dd50498..d92d80f 100644
--- a/lib/CodeGen/RegAllocBasic.cpp
+++ b/lib/CodeGen/RegAllocBasic.cpp
@@ -278,6 +278,7 @@
<< " to " << PrintReg(PhysReg, TRI) << '\n');
assert(!VRM->hasPhys(VirtReg.reg) && "Duplicate VirtReg assignment");
VRM->assignVirt2Phys(VirtReg.reg, PhysReg);
+ MRI->setPhysRegUsed(PhysReg);
PhysReg2LiveUnion[PhysReg].unify(VirtReg);
++NumAssigned;
}