Fix PR5391: support early clobber physical register def tied with a use (ewwww)

- A valno should be set HasRedefByEC if there is an early clobber def in the middle of its live ranges. It should not be set if the def of the valno is defined by an early clobber.
- If a physical register def is tied to an use and it's an early clobber, it just means the HasRedefByEC is set since it's still one continuous live range.
- Add a couple of missing checks for HasRedefByEC in the coalescer. In general, it should not coalesce a vr with a physical register if the physical register has a early clobber def somewhere. This is overly conservative but that's the price for using such a nasty inline asm "feature".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90269 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 12 insertions, 4 deletions

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 24adf364e7..3c1d4b3ccd 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -374,8 +374,6 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
       // Value#0 is now defined by the 2-addr instruction.
       OldValNo->def  = RedefIndex;
       OldValNo->setCopy(0);
-      if (MO.isEarlyClobber())
-        OldValNo->setHasRedefByEC(true);
       
       // Add the new live interval which replaces the range for the input copy.
       LiveRange LR(DefIndex, RedefIndex, ValNo);
@@ -513,8 +511,6 @@ void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
         if (mi->isRegTiedToUseOperand(DefIdx)) {
           // Two-address instruction.
           end = baseIndex.getDefIndex();
-          assert(!mi->getOperand(DefIdx).isEarlyClobber() &&
-                 "Two address instruction is an early clobber?"); 
         } else {
           // Another instruction redefines the register before it is ever read.
           // Then the register is essentially dead at the instruction that defines
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 58763718f9..cb2d22b6c9 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1938,6 +1938,10 @@ bool SimpleRegisterCoalescing::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS){
     if (Overlaps) {
       // If we haven't already recorded that this value # is safe, check it.
       if (!InVector(LHSIt->valno, EliminatedLHSVals)) {
+        // If it's re-defined by an early clobber somewhere in the live range,
+        // then conservatively abort coalescing.
+        if (LHSIt->valno->hasRedefByEC())
+          return false;
         // Copy from the RHS?
         if (!RangeIsDefinedByCopyFromReg(LHS, LHSIt, RHS.reg))
           return false;    // Nope, bail out.
@@ -1977,6 +1981,10 @@ bool SimpleRegisterCoalescing::SimpleJoin(LiveInterval &LHS, LiveInterval &RHS){
           // if coalescing succeeds.  Just skip the liverange.
           if (++LHSIt == LHSEnd) break;
         } else {
+          // If it's re-defined by an early clobber somewhere in the live range,
+          // then conservatively abort coalescing.
+          if (LHSIt->valno->hasRedefByEC())
+            return false;
           // Otherwise, if this is a copy from the RHS, mark it as being merged
           // in.
           if (RangeIsDefinedByCopyFromReg(LHS, LHSIt, RHS.reg)) {
@@ -2316,6 +2324,10 @@ SimpleRegisterCoalescing::JoinIntervals(LiveInterval &LHS, LiveInterval &RHS,
       if (LHSValNoAssignments[I->valno->id] !=
           RHSValNoAssignments[J->valno->id])
         return false;
+      // If it's re-defined by an early clobber somewhere in the live range,
+      // then conservatively abort coalescing.
+      if (NewVNInfo[LHSValNoAssignments[I->valno->id]]->hasRedefByEC())
+        return false;
     }
 
     if (I->end < J->end) {