Remove val# defined by a remat'ed def that is now dead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58294 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 77 insertions, 2 deletions

diff --git a/lib/CodeGen/PreAllocSplitting.cpp b/lib/CodeGen/PreAllocSplitting.cpp
index 33e3e8054c..09694403e3 100644
--- a/lib/CodeGen/PreAllocSplitting.cpp
+++ b/lib/CodeGen/PreAllocSplitting.cpp
@@ -561,6 +561,9 @@ bool PreAllocSplitting::SplitRegLiveInterval(LiveInterval *LI) {
     SpillMI = prior(SpillPt);
     LIs->InsertMachineInstrInMaps(SpillMI, SpillIndex);
   } else if (!PrevSpilled) {
+    if (!DefMI)
+      // Def is dead. Do nothing.
+      return false;
     // If it's already split, just restore the value. There is no need to spill
     // the def again.
     // Check if it's possible to insert a spill after the def MI.
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 6eeb21c1bf..a60939c301 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -707,6 +707,18 @@ bool SimpleRegisterCoalescing::ShortenDeadCopyLiveRange(LiveInterval &li,
   return false;
 }
 
+/// RemoveDeadDef - If a def of a live interval is now determined dead, remove
+/// the val# it defines. If the live interval becomes empty, remove it as well.
+bool SimpleRegisterCoalescing::RemoveDeadDef(LiveInterval &li,
+                                             MachineInstr *DefMI) {
+  unsigned DefIdx = li_->getDefIndex(li_->getInstructionIndex(DefMI));
+  LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
+  if (DefIdx != MLR->valno->def)
+    return false;
+  li.removeValNo(MLR->valno);
+  return removeIntervalIfEmpty(li, li_, tri_);
+}
+
 /// PropagateDeadness - Propagate the dead marker to the instruction which
 /// defines the val#.
 static void PropagateDeadness(LiveInterval &li, MachineInstr *CopyMI,
@@ -2280,6 +2292,7 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
 
   // Perform a final pass over the instructions and compute spill weights
   // and remove identity moves.
+  SmallVector<unsigned, 4> DeadDefs;
   for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
        mbbi != mbbe; ++mbbi) {
     MachineBasicBlock* mbb = mbbi;
@@ -2313,9 +2326,13 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
         bool isDead = true;
         for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
           const MachineOperand &MO = MI->getOperand(i);
-          if (!MO.isReg() || MO.isDead())
+          if (!MO.isReg())
             continue;
           unsigned Reg = MO.getReg();
+          if (TargetRegisterInfo::isVirtualRegister(Reg))
+            DeadDefs.push_back(Reg);
+          if (MO.isDead())
+            continue;
           if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
               !mri_->use_empty(Reg)) {
             isDead = false;
@@ -2323,10 +2340,16 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
           }
         }
         if (isDead) {
+          while (!DeadDefs.empty()) {
+            unsigned DeadDef = DeadDefs.back();
+            DeadDefs.pop_back();
+            RemoveDeadDef(li_->getInterval(DeadDef), MI);
+          }
           li_->RemoveMachineInstrFromMaps(mii);
           mii = mbbi->erase(mii);
           continue;
-        }
+        } else
+          DeadDefs.clear();
       }
 
       // If the move will be an identity move delete it
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.h b/lib/CodeGen/SimpleRegisterCoalescing.h
index 330c476dbf..abe392990d 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.h
+++ b/lib/CodeGen/SimpleRegisterCoalescing.h
@@ -269,6 +269,11 @@ namespace llvm {
     /// live range is dead. Return true if live interval is removed.
     bool ShortenDeadCopySrcLiveRange(LiveInterval &li, MachineInstr *CopyMI);
 
+    /// RemoveDeadDef - If a def of a live interval is now determined dead,
+    /// remove the val# it defines. If the live interval becomes empty, remove
+    /// it as well.
+    bool RemoveDeadDef(LiveInterval &li, MachineInstr *DefMI);
+
     /// lastRegisterUse - Returns the last use of the specific register between
     /// cycles Start and End or NULL if there are no uses.
     MachineOperand *lastRegisterUse(unsigned Start, unsigned End, unsigned Reg,
diff --git a/test/CodeGen/X86/2008-10-27-CoalescerBug.ll b/test/CodeGen/X86/2008-10-27-CoalescerBug.ll
new file mode 100644
index 0000000000..2c8e12fb26
--- /dev/null
+++ b/test/CodeGen/X86/2008-10-27-CoalescerBug.ll
@@ -0,0 +1,44 @@
+; RUN: llvm-as < %s | llc -march=x86 -mattr=+sse2 -stats |& not grep {Number of register spills}
+
+define fastcc void @fourn(double* %data, i32 %isign) nounwind {
+entry:
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%indvar93 = phi i32 [ 0, %entry ], [ %idim.030, %bb ]		; <i32> [#uses=2]
+	%idim.030 = add i32 %indvar93, 1		; <i32> [#uses=1]
+	%0 = add i32 %indvar93, 2		; <i32> [#uses=1]
+	%1 = icmp sgt i32 %0, 2		; <i1> [#uses=1]
+	br i1 %1, label %bb30.loopexit, label %bb
+
+bb3:		; preds = %bb30.loopexit, %bb25, %bb3
+	%2 = load i32* null, align 4		; <i32> [#uses=1]
+	%3 = mul i32 %2, 0		; <i32> [#uses=1]
+	%4 = icmp slt i32 0, %3		; <i1> [#uses=1]
+	br i1 %4, label %bb18, label %bb3
+
+bb18:		; preds = %bb3
+	%5 = fdiv double %11, 0.000000e+00		; <double> [#uses=1]
+	%6 = tail call double @sin(double %5) nounwind readonly		; <double> [#uses=1]
+	br label %bb24.preheader
+
+bb22.preheader:		; preds = %bb24.preheader, %bb22.preheader
+	br label %bb22.preheader
+
+bb25:		; preds = %bb24.preheader
+	%7 = mul double 0.000000e+00, %6		; <double> [#uses=0]
+	%8 = add i32 %i3.122100, 0		; <i32> [#uses=1]
+	%9 = icmp sgt i32 %8, 0		; <i1> [#uses=1]
+	br i1 %9, label %bb3, label %bb24.preheader
+
+bb24.preheader:		; preds = %bb25, %bb18
+	%i3.122100 = or i32 0, 1		; <i32> [#uses=2]
+	%10 = icmp slt i32 0, %i3.122100		; <i1> [#uses=1]
+	br i1 %10, label %bb25, label %bb22.preheader
+
+bb30.loopexit:		; preds = %bb
+	%11 = mul double 0.000000e+00, 0x401921FB54442D1C		; <double> [#uses=1]
+	br label %bb3
+}
+
+declare double @sin(double) nounwind readonly