When the register allocator runs out of registers, spill a physical register around the def's and use's of the interval being allocated to make it possible for the interval to target a register and spill it right away and restore a register for uses. This likely generates terrible code but is before than aborting.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48218 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index d43cc19..12e7d6a 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -561,6 +561,7 @@
// is very bad (it contains all callee clobbered registers for any functions
// with a call), so we want to avoid doing that if possible.
unsigned physReg = getFreePhysReg(cur);
+ unsigned BestPhysReg = physReg;
if (physReg) {
// We got a register. However, if it's in the fixed_ list, we might
// conflict with it. Check to see if we conflict with it or any of its
@@ -685,8 +686,27 @@
}
// All registers must have inf weight. Just grab one!
- if (!minReg)
- minReg = *RC->allocation_order_begin(*mf_);
+ if (!minReg) {
+ if (BestPhysReg)
+ minReg = BestPhysReg;
+ else {
+ // Get the physical register with the fewest conflicts.
+ unsigned MinConflicts = ~0U;
+ for (TargetRegisterClass::iterator i = RC->allocation_order_begin(*mf_),
+ e = RC->allocation_order_end(*mf_); i != e; ++i) {
+ unsigned reg = *i;
+ unsigned NumConflicts = li_->getNumConflictsWithPhysReg(*cur, reg);
+ if (NumConflicts <= MinConflicts) {
+ MinConflicts = NumConflicts;
+ minReg = reg;
+ }
+ }
+ }
+
+ if (cur->weight == HUGE_VALF || cur->getSize() == 1)
+ // Spill a physical register around defs and uses.
+ li_->spillPhysRegAroundRegDefsUses(*cur, minReg, *vrm_);
+ }
}
DOUT << "\t\tregister with min weight: "