A value defined by an implicit_def can be liven to a use BB. This is unfortunate. But register allocator still has to add it to the live-in set of the use BB.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72889 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index 0ef97c1..ab4068e 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -542,6 +542,24 @@
// Ignore splited live intervals.
if (!isPhys && vrm_->getPreSplitReg(cur.reg))
continue;
+
+ // A register defined by an implicit_def can be liveout the def BB and livein
+ // to a use BB. Add it to the livein set of the use BB's.
+ if (!isPhys && cur.empty()) {
+ if (MachineInstr *DefMI = mri_->getVRegDef(cur.reg)) {
+ assert(DefMI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF);
+ MachineBasicBlock *DefMBB = DefMI->getParent();
+ SmallPtrSet<MachineBasicBlock*, 4> Seen;
+ Seen.insert(DefMBB);
+ for (MachineRegisterInfo::reg_iterator ri = mri_->reg_begin(cur.reg),
+ re = mri_->reg_end(); ri != re; ++ri) {
+ MachineInstr *UseMI = &*ri;
+ MachineBasicBlock *UseMBB = UseMI->getParent();
+ if (Seen.insert(UseMBB))
+ UseMBB->addLiveIn(Reg);
+ }
+ }
+ }
for (LiveInterval::Ranges::const_iterator I = cur.begin(), E = cur.end();
I != E; ++I) {
const LiveRange &LR = *I;