Provide a target override for the cost of using a callee-saved register
for the first time.
Thanks Andy for the discussion.
rdar://16162005
llvm-svn: 204979
diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
index 0eb91ab..6a623b8 100644
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -2123,7 +2123,10 @@
unsigned PhysReg,
unsigned &CostPerUseLimit,
SmallVectorImpl<unsigned> &NewVRegs) {
- BlockFrequency CSRCost(CSRFirstTimeCost);
+ // We use the larger one out of the command-line option and the value report
+ // by TRI.
+ BlockFrequency CSRCost(std::max((unsigned)CSRFirstTimeCost,
+ TRI->getCSRFirstUseCost()));
if (getStage(VirtReg) == RS_Spill && VirtReg.isSpillable()) {
// We choose spill over using the CSR for the first time if the spill cost
// is lower than CSRCost.
@@ -2172,7 +2175,8 @@
// When NewVRegs is not empty, we may have made decisions such as evicting
// a virtual register, go with the earlier decisions and use the physical
// register.
- if (CSRFirstTimeCost > 0 && CSRFirstUse && NewVRegs.empty()) {
+ if ((CSRFirstTimeCost || TRI->getCSRFirstUseCost()) &&
+ CSRFirstUse && NewVRegs.empty()) {
unsigned CSRReg = tryAssignCSRFirstTime(VirtReg, Order, PhysReg,
CostPerUseLimit, NewVRegs);
if (CSRReg || !NewVRegs.empty())