Handle overlapping regunit intervals in LiveIntervals::addKillFlags().
We will soon allow virtual register live ranges to overlap regunit live
ranges when the physreg is defined as a copy of the virtreg:
%EAX = COPY %vreg5
FOO %vreg5
BAR %EAX<kill>
There is no real interference since %vreg5 and %EAX have the same value
where they overlap.
This patch prevents addKillFlags from adding virtreg kill flags to FOO
where the assigned physreg is overlapping the virtual register live
range.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163335 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index bdf4f2d..b447c3c 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -34,6 +34,7 @@
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/STLExtras.h"
#include "LiveRangeCalc.h"
+#include "VirtRegMap.h"
#include <algorithm>
#include <limits>
#include <cmath>
@@ -733,12 +734,28 @@
// Register allocator hooks.
//
-void LiveIntervals::addKillFlags() {
+void LiveIntervals::addKillFlags(const VirtRegMap *VRM) {
+ // Keep track of regunit ranges.
+ SmallVector<std::pair<LiveInterval*, LiveInterval::iterator>, 8> RU;
+
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (MRI->reg_nodbg_empty(Reg))
continue;
LiveInterval *LI = &getInterval(Reg);
+ if (LI->empty())
+ continue;
+
+ // Find the regunit intervals for the assigned register. They may overlap
+ // the virtual register live range, cancelling any kills.
+ RU.clear();
+ for (MCRegUnitIterator Units(VRM->getPhys(Reg), TRI); Units.isValid();
+ ++Units) {
+ LiveInterval *RUInt = &getRegUnit(*Units);
+ if (RUInt->empty())
+ continue;
+ RU.push_back(std::make_pair(RUInt, RUInt->find(LI->begin()->end)));
+ }
// Every instruction that kills Reg corresponds to a live range end point.
for (LiveInterval::iterator RI = LI->begin(), RE = LI->end(); RI != RE;
@@ -749,7 +766,32 @@
MachineInstr *MI = getInstructionFromIndex(RI->end);
if (!MI)
continue;
- MI->addRegisterKilled(Reg, NULL);
+
+ // Check if any of the reguints are live beyond the end of RI. That could
+ // happen when a physreg is defined as a copy of a virtreg:
+ //
+ // %EAX = COPY %vreg5
+ // FOO %vreg5 <--- MI, cancel kill because %EAX is live.
+ // BAR %EAX<kill>
+ //
+ // There should be no kill flag on FOO when %vreg5 is rewritten as %EAX.
+ bool CancelKill = false;
+ for (unsigned u = 0, e = RU.size(); u != e; ++u) {
+ LiveInterval *RInt = RU[u].first;
+ LiveInterval::iterator &I = RU[u].second;
+ if (I == RInt->end())
+ continue;
+ I = RInt->advanceTo(I, RI->end);
+ if (I == RInt->end() || I->start >= RI->end)
+ continue;
+ // I is overlapping RI.
+ CancelKill = true;
+ break;
+ }
+ if (CancelKill)
+ MI->clearRegisterKills(Reg, NULL);
+ else
+ MI->addRegisterKilled(Reg, NULL);
}
}
}