diff options
Diffstat (limited to 'lib/CodeGen/SimpleRegisterCoalescing.cpp')
| -rw-r--r-- | lib/CodeGen/SimpleRegisterCoalescing.cpp | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp index 93aa0a3120..c621726a03 100644 --- a/lib/CodeGen/SimpleRegisterCoalescing.cpp +++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp @@ -919,13 +919,23 @@ SimpleRegisterCoalescing::ShortenDeadCopySrcLiveRange(LiveInterval &li, /// are not spillable! If the destination interval uses are far away, think /// twice about coalescing them! bool SimpleRegisterCoalescing::shouldJoinPhys(CoalescerPair &CP) { + bool Allocatable = li_->isAllocatable(CP.getDstReg()); + LiveInterval &JoinVInt = li_->getInterval(CP.getSrcReg()); + + /// Always join simple intervals that are defined by a single copy from a + /// reserved register. This doesn't increase register pressure, so it is + /// always beneficial. + if (!Allocatable && CP.isFlipped() && JoinVInt.containsOneValue()) + return true; + if (DisablePhysicalJoin) { DEBUG(dbgs() << "\tPhysreg joins disabled.\n"); return false; } - // Only coalesce to allocatable physreg. - if (!li_->isAllocatable(CP.getDstReg())) { + // Only coalesce to allocatable physreg, we don't want to risk modifying + // reserved registers. + if (!Allocatable) { DEBUG(dbgs() << "\tRegister is an unallocatable physreg.\n"); return false; // Not coalescable. } @@ -944,8 +954,6 @@ bool SimpleRegisterCoalescing::shouldJoinPhys(CoalescerPair &CP) { // FIXME: Why are we skipping this test for partial copies? // CodeGen/X86/phys_subreg_coalesce-3.ll needs it. if (!CP.isPartial()) { - LiveInterval &JoinVInt = li_->getInterval(CP.getSrcReg()); - const TargetRegisterClass *RC = mri_->getRegClass(CP.getSrcReg()); unsigned Threshold = allocatableRCRegs_[RC].count() * 2; unsigned Length = li_->getApproximateInstructionCount(JoinVInt); |