[PowerPC] Use mtocrf when available

Just as with mfocrf, it is also preferable to use mtocrf instead of
mtcrf when only a single CR register is to be written.

Current code however always emits mtcrf.  This probably does not matter
when using an external assembler, since the GNU assembler will in fact
automatically replace mtcrf with mtocrf when possible.  It does create
inefficient code with the integrated assembler, however.

To fix this, this patch adds MTOCRF/MTOCRF8 instruction patterns and
uses those instead of MTCRF/MTCRF8 everything.  Just as done in the
MFOCRF patch committed as 185556, these patterns will be converted
back to MTCRF if MTOCRF is not available on the machine.

As a side effect, this allows to modify the MTCRF pattern to accept
the full range of mask operands for the benefit of the asm parser.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185561 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/Target/PowerPC/PPCAsmPrinter.cpp b/lib/Target/PowerPC/PPCAsmPrinter.cpp
index 5129287e17..8f41b2e7f7 100644
--- a/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -676,6 +676,23 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
       return;
     }
     break;
+  case PPC::MTOCRF:
+  case PPC::MTOCRF8:
+    if (!Subtarget.hasMFOCRF()) {
+      // Transform: %CR7 = MTOCRF %R3
+      // Into:      MTCRF mask, %R3 ;; cr7
+      unsigned NewOpcode =
+        MI->getOpcode() == PPC::MTOCRF ? PPC::MTCRF : PPC::MTCRF8;
+      unsigned Mask = 0x80 >> OutContext.getRegisterInfo()
+                              ->getEncodingValue(MI->getOperand(0).getReg());
+      OutStreamer.AddComment(PPCInstPrinter::
+                             getRegisterName(MI->getOperand(0).getReg()));
+      OutStreamer.EmitInstruction(MCInstBuilder(NewOpcode)
+                                  .addImm(Mask)
+                                  .addReg(MI->getOperand(1).getReg()));
+      return;
+    }
+    break;
   case PPC::SYNC:
     // In Book E sync is called msync, handle this special case here...
     if (Subtarget.isBookE()) {