[CodeGen] Remove target SubRegLiveness flags (#95437)

This removes the uses of target flags to disable subreg liveness,
relying on the `-enable-subreg-liveness` flag instead. The
`-enable-subreg-liveness` flag has been changed to take precedence over
the subtarget if set, and one use of `Subtarget->enableSubRegLiveness()`
has been changed to `MRI->subRegLivenessEnabled()` to make sure the
option properly applies.

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/MachineRegisterInfo.cpp b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
index b0c1838b..3caa96c 100644
--- a/llvm/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
@@ -41,8 +41,10 @@ static cl::opt<bool> EnableSubRegLiveness("enable-subreg-liveness", cl::Hidden,
 void MachineRegisterInfo::Delegate::anchor() {}
 
 MachineRegisterInfo::MachineRegisterInfo(MachineFunction *MF)
-    : MF(MF), TracksSubRegLiveness(MF->getSubtarget().enableSubRegLiveness() &&
-                                   EnableSubRegLiveness) {
+    : MF(MF),
+      TracksSubRegLiveness(EnableSubRegLiveness.getNumOccurrences()
+                               ? EnableSubRegLiveness
+                               : MF->getSubtarget().enableSubRegLiveness()) {
   unsigned NumRegs = getTargetRegisterInfo()->getNumRegs();
   VRegInfo.reserve(256);
   RegAllocHints.reserve(256);