[SystemZ] Add TM and TMY

The main complication here is that TM and TMY (the memory forms) set
CC differently from the register forms.  When the tested bits contain
some 0s and some 1s, the register forms set CC to 1 or 2 based on the
value the uppermost bit.  The memory forms instead set CC to 1
regardless of the uppermost bit.

Until now, I've tried to make it so that a branch never tests for an
impossible CC value.  E.g. NR only sets CC to 0 or 1, so branches on the
result will only test for 0 or 1.  Originally I'd tried to do the same
thing for TM and TMY by using custom matching code in ISelDAGToDAG.
That ended up being very ugly though, and would have meant duplicating
some of the chain checks that the common isel code does.

I've therefore gone for the simpler alternative of adding an extra
operand to the TM DAG opcode to say whether a memory form would be OK.
This means that the inverse of a "TM;JE" is "TM;JNE" rather than the
more precise "TM;JNLE", just like the inverse of "TMLL;JE" is "TMLL;JNE".
I suppose that's arguably less confusing though...


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190400 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 6 deletions

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 9fc56fe916..5528404a19 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -1226,13 +1226,13 @@ static unsigned getTestUnderMaskCond(unsigned BitSize, unsigned CCMask,
   return 0;
 }
 
-// See whether the comparison (Opcode CmpOp0, CmpOp1) can be implemented
-// as a TEST UNDER MASK instruction when the condition being tested is
-// as described by CCValid and CCMask.  Update the arguments with the
-// TM version if so.
+// See whether the comparison (Opcode CmpOp0, CmpOp1, ICmpType) can be
+// implemented as a TEST UNDER MASK instruction when the condition being
+// tested is as described by CCValid and CCMask.  Update the arguments
+// with the TM version if so.
 static void adjustForTestUnderMask(unsigned &Opcode, SDValue &CmpOp0,
                                    SDValue &CmpOp1, unsigned &CCValid,
-                                   unsigned &CCMask, unsigned ICmpType) {
+                                   unsigned &CCMask, unsigned &ICmpType) {
   // Check that we have a comparison with a constant.
   ConstantSDNode *ConstCmpOp1 = dyn_cast<ConstantSDNode>(CmpOp1);
   if (!ConstCmpOp1)
@@ -1266,6 +1266,8 @@ static void adjustForTestUnderMask(unsigned &Opcode, SDValue &CmpOp0,
   Opcode = SystemZISD::TM;
   CmpOp0 = AndOp0;
   CmpOp1 = AndOp1;
+  ICmpType = (bool(NewCCMask & SystemZ::CCMASK_TM_MIXED_MSB_0) !=
+              bool(NewCCMask & SystemZ::CCMASK_TM_MIXED_MSB_1));
   CCValid = SystemZ::CCMASK_TM;
   CCMask = NewCCMask;
 }
@@ -1315,7 +1317,7 @@ static SDValue emitCmp(const SystemZTargetMachine &TM, SelectionDAG &DAG,
   }
 
   adjustForTestUnderMask(Opcode, CmpOp0, CmpOp1, CCValid, CCMask, ICmpType);
-  if (Opcode == SystemZISD::ICMP)
+  if (Opcode == SystemZISD::ICMP || Opcode == SystemZISD::TM)
     return DAG.getNode(Opcode, DL, MVT::Glue, CmpOp0, CmpOp1,
                        DAG.getConstant(ICmpType, MVT::i32));
   return DAG.getNode(Opcode, DL, MVT::Glue, CmpOp0, CmpOp1);