Coalescer should not delete copy instructions whose defs are partially dead. e.g.

%RDI<def,dead> = MOV64rr %RAX<kill>, %EDI<imp-def>

llvm-svn: 100804

2 files changed, 14 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index f2ba484e4f0..9f03b5bac70 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1125,6 +1125,19 @@ unsigned MachineInstr::isConstantValuePHI() const {
   return Reg;
 }
 
+/// allDefsAreDead - Return true if all the defs of this instruction are dead.
+///
+bool MachineInstr::allDefsAreDead() const {
+  for (unsigned i = 0, e = getNumOperands(); i < e; ++i) {
+    const MachineOperand &MO = getOperand(i);
+    if (!MO.isReg() || MO.isUse())
+      continue;
+    if (!MO.isDead())
+      return false;
+  }
+  return true;
+}
+
 void MachineInstr::dump() const {
   dbgs() << "  " << *this;
 }
diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 15ca3740b8f..1f9d726143a 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -2744,7 +2744,7 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
             // delete them later.
             DoDelete = false;
         }
-        if (MI->registerDefIsDead(DstReg)) {
+        if (MI->allDefsAreDead()) {
           LiveInterval &li = li_->getInterval(DstReg);
           if (!ShortenDeadCopySrcLiveRange(li, MI))
             ShortenDeadCopyLiveRange(li, MI);