[MachineSink] Don't reject sinking because of dead def in isProfitableToSinkTo().

An instruction should be sunk (if otherwise legal and profitable) regardless
of if it has a dead def of a physreg or not. Physreg defs are checked in other
places and sinking is only done with dead defs of regs that are not live into
the target MBB.

Differential Revision: https://reviews.llvm.org/D150447

Reviewed By: sebastian-ne, arsenm

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 5047503..1bd3705 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -806,12 +806,10 @@ bool MachineSinking::isProfitableToSinkTo(Register Reg, MachineInstr &MI,
       continue;
 
     if (Reg.isPhysical()) {
-      if (MO.isUse() &&
-          (MRI->isConstantPhysReg(Reg) || TII->isIgnorableUse(MO)))
-        continue;
-
-      // Don't handle non-constant and non-ignorable physical register.
-      return false;
+      // Don't handle non-constant and non-ignorable physical register uses.
+      if (MO.isUse() && !MRI->isConstantPhysReg(Reg) && !TII->isIgnorableUse(MO))
+        return false;
+      continue;
     }
 
     // Users for the defs are all dominated by SuccToSinkTo.