[PowerPC] Always use mfocrf if available

When accessing just a single CR register, it is always preferable to
use mfocrf instead of mfcr, if the former is available on the CPU.

Current code makes that distinction in many, but not all places
where a single CR register value is retrieved.  One missing
location is PPCRegisterInfo::lowerCRSpilling.

To fix this and make this simpler in the future, this patch changes
the bulk of the back-end to always assume mfocrf is available and
simply generate it when needed.

On machines that actually do not support mfocrf, the instruction
is replaced by mfcr at the very end, in EmitInstruction.

This has the additional benefit that we no longer need the
MFCRpseud hack, since before EmitInstruction we always have
a MFOCRF instruction pattern, which already models data flow
as required.

The patch also adds the MFOCRF8 version of the instruction,
which was missing so far.

Except for the PPCRegisterInfo::lowerCRSpilling case, no change
in generated code intended.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185556 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 6 deletions

diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index 3378ace..db49e21 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -626,7 +626,7 @@ const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
   case PPCISD::RET_FLAG:        return "PPCISD::RET_FLAG";
   case PPCISD::EH_SJLJ_SETJMP:  return "PPCISD::EH_SJLJ_SETJMP";
   case PPCISD::EH_SJLJ_LONGJMP: return "PPCISD::EH_SJLJ_LONGJMP";
-  case PPCISD::MFCR:            return "PPCISD::MFCR";
+  case PPCISD::MFOCRF:          return "PPCISD::MFOCRF";
   case PPCISD::VCMP:            return "PPCISD::VCMP";
   case PPCISD::VCMPo:           return "PPCISD::VCMPo";
   case PPCISD::LBRX:            return "PPCISD::LBRX";
@@ -5539,7 +5539,7 @@ SDValue PPCTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
 
   // Now that we have the comparison, emit a copy from the CR to a GPR.
   // This is flagged to the above dot comparison.
-  SDValue Flags = DAG.getNode(PPCISD::MFCR, dl, MVT::i32,
+  SDValue Flags = DAG.getNode(PPCISD::MFOCRF, dl, MVT::i32,
                                 DAG.getRegister(PPC::CR6, MVT::i32),
                                 CompNode.getValue(1));
 
@@ -7293,16 +7293,16 @@ SDValue PPCTargetLowering::PerformDAGCombine(SDNode *N,
         }
       }
 
-      // If the user is a MFCR instruction, we know this is safe.  Otherwise we
-      // give up for right now.
-      if (FlagUser->getOpcode() == PPCISD::MFCR)
+      // If the user is a MFOCRF instruction, we know this is safe.
+      // Otherwise we give up for right now.
+      if (FlagUser->getOpcode() == PPCISD::MFOCRF)
         return SDValue(VCMPoNode, 0);
     }
     break;
   }
   case ISD::BR_CC: {
     // If this is a branch on an altivec predicate comparison, lower this so
-    // that we don't have to do a MFCR: instead, branch directly on CR6.  This
+    // that we don't have to do a MFOCRF: instead, branch directly on CR6.  This
     // lowering is done pre-legalize, because the legalizer lowers the predicate
     // compare down to code that is difficult to reassemble.
     ISD::CondCode CC = cast<CondCodeSDNode>(N->getOperand(1))->get();