Don't add <imp-def> operands during register rewriting.

LiveIntervals already adds <imp-def> operands for super-registers when a subreg
def defines the whole register. Thus, it is not necessary to do it again when
rewriting.

In fact, the super-register imp-defs caused miscompilations because the late
scheduler couldn't see that the super-register was read.

We still add super-reg <imp-use,kill> operands when rewriting virtuals to
physicals.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113299 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 16 deletions

diff --git a/lib/CodeGen/VirtRegRewriter.cpp b/lib/CodeGen/VirtRegRewriter.cpp
index d988e106c5..240d28cf30 100644
--- a/lib/CodeGen/VirtRegRewriter.cpp
+++ b/lib/CodeGen/VirtRegRewriter.cpp
@@ -67,23 +67,16 @@ VirtRegRewriter::~VirtRegRewriter() {}
 /// Note that operands may be added, so the MO reference is no longer valid.
 static void substitutePhysReg(MachineOperand &MO, unsigned Reg,
                               const TargetRegisterInfo &TRI) {
-  if (unsigned SubIdx = MO.getSubReg()) {
-    // Insert the physical subreg and reset the subreg field.
-    MO.setReg(TRI.getSubReg(Reg, SubIdx));
-    MO.setSubReg(0);
-
-    // Any def, dead, and kill flags apply to the full virtual register, so they
-    // also apply to the full physical register. Add imp-def/dead and imp-kill
-    // as needed.
+  if (MO.getSubReg()) {
+    MO.substPhysReg(Reg, TRI);
+
+    // Any kill flags apply to the full virtual register, so they also apply to
+    // the full physical register.
+    // We assume that partial defs have already been decorated with a super-reg
+    // <imp-def> operand by LiveIntervals.
     MachineInstr &MI = *MO.getParent();
-    if (MO.isDef())
-      if (MO.isDead())
-        MI.addRegisterDead(Reg, &TRI, /*AddIfNotFound=*/ true);
-      else
-        MI.addRegisterDefined(Reg, &TRI);
-    else if (!MO.isUndef() &&
-             (MO.isKill() ||
-              MI.isRegTiedToDefOperand(&MO-&MI.getOperand(0))))
+    if (MO.isUse() && !MO.isUndef() &&
+        (MO.isKill() || MI.isRegTiedToDefOperand(&MO-&MI.getOperand(0))))
       MI.addRegisterKilled(Reg, &TRI, /*AddIfNotFound=*/ true);
   } else {
     MO.setReg(Reg);