[PowerPC] Exploit the rlwinm + rlwinm when "and" with constant

[Esme]

Summary

If it is "and" with constant, for some special pattern, we could use the rotate and instructions instead of the "andi." which requires us to generate the mask using several instructions. i.e. If the mask looks like this. That is, it has two groups of ones, and all of them are within the bits [32, 63].

    MB  MB2    ME2 ME           
+----------------------+    
|0001111100000011111000| 
+----------------------+    
 0 32                 64

We could optimize it as:

1. Clear the bit (MB2, ME2) first. It is a warpping mask. RLWINM 0, ME2, MB2

    MB  MB2    ME2 ME           MB  MB2    ME2 ME
+----------------------+    +----------------------+
|1111111111111111111111| -> |1111111100000011111111+
+----------------------+    +----------------------+
 0 32                 64     0 32                  64

2. Clear the bit (ME, MB). Notice that, as RLWINM will update the bit [0, 31], we can only do this optimization if MB >= 32.

    MB  MB2    ME2 ME           MB  MB2    ME2 ME
+----------------------+    +----------------------+
|1111111100000011111111| -> |0001111100000011111000+
+----------------------+    +----------------------+
 0 32                 64     0 32                 64

[steven.zhang]

Rebase the patch.

[Esme]

D93894 covers this patch.

llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp

 private:
     bool trySETCC(SDNode *N);
     bool tryAsSingleRLDICL(SDNode *N);
     bool tryAsSingleRLDICR(SDNode *N);
     bool tryAsSingleRLWINM(SDNode *N);
     bool tryAsSingleRLWINM8(SDNode *N);
     bool tryAsSingleRLWIMI(SDNode *N);
     bool tryAsPairOfRLDICL(SDNode *N);
+    bool tryAsPairOfRLWINM8(SDNode *N);
 
     void PeepholePPC64();
     void PeepholePPC64ZExt();
     void PeepholeCROps();
 
     SDValue combineToCMPB(SDNode *N);
     void foldBoolExts(SDValue &Res, SDNode *&N);
 
bool PPCDAGToDAGISel::tryAsPairOfRLDICL(SDNode *N) {
   // +----------------------+    +----------------------+
   //  0          32        64     0          32        64
   // Rotate back and then, clear the bits [0, MB)
   SDValue Ops[] = {Val, getI64Imm(63 - MB2, Loc), getI64Imm(MB, Loc)};
   CurDAG->SelectNodeTo(N, PPC::RLDICL, MVT::i64, Ops);
   return true;
 }
 
+bool PPCDAGToDAGISel::tryAsPairOfRLWINM8(SDNode *N) {
+  assert(N->getOpcode() == ISD::AND && "ISD::AND SDNode expected");
+  uint64_t Imm64;
+  if (!isInt64Immediate(N->getOperand(1).getNode(), Imm64))
+    return false;
+
+  // Do nothing if it is 16-bit imm as the pattern in the .td file handle
+  // it well with "andi.".
+  if (isUInt<16>(Imm64))
+    return false;
+
+  // We can do special handling for pattern like this.
+  //     MB  MB2    ME2 ME
+  // +----------------------+
+  // |0001111100000011111000|
+  // +----------------------+
+  unsigned MB = countLeadingZeros(Imm64);
+  unsigned ME = 63 - countTrailingZeros(Imm64);
+  // Get the invert mask of [MB, ME].
+  uint64_t InvertMask =
+      ~Imm64 & APInt::getBitsSet(64, 63 - ME, 64 - MB).getZExtValue();
+  unsigned MB2, ME2;
+  if (!isRunOfOnes64(InvertMask, MB2, ME2))
+    return false;
+  // Correct the MB2 and ME2 to be the position of last '1' of the first ones,
+  // and the position of first '1' of the second ones.
+  MB2--;
+  ME2++;
+  assert(MB2 <= ME2 && "Invalid MB and ME");
+
+  if (MB < 32)
+    return false;
+
+  // If it is within [32, 64), we can optimize it with two rlwinm.
+  //     MB  MB2    ME2 ME           MB  MB2    ME2 ME
+  // +----------------------+    +----------------------+
+  // |1111111111111111111111| -> |1111111100000011111111+
+  // +----------------------+    +----------------------+
+  //  0          32        64     0          32        64
+  // Clear the bit (MB2, ME2) first. It is a warpping mask.
+  // RLWINM 0, ME2, MB2
+  SDLoc Loc(N);
+  SDValue Val = N->getOperand(0);
+  Val = SDValue(
+      CurDAG->getMachineNode(PPC::RLWINM8, Loc, MVT::i64,
+                             {Val, getI64Imm(0, Loc), getI64Imm(ME2 - 32, Loc),
+                              getI64Imm(MB2 - 32, Loc)}),
+      0);
+  //     MB  MB2    ME2 ME           MB  MB2    ME2 ME
+  // +----------------------+    +----------------------+
+  // |1111111100000011111111| -> |0001111100000011111000+
+  // +----------------------+    +----------------------+
+  //  0          32        64     0 32                 64
+  // Clear the bit (ME, MB). Notice that, as RLWINM will update the bit
+  // [0, 31], we can only do this optimization if MB >= 32.
+  SDValue Ops[] = {Val, getI64Imm(0, Loc), getI64Imm(MB - 32, Loc),
+                   getI64Imm(ME - 32, Loc)};
+  CurDAG->SelectNodeTo(N, PPC::RLWINM8, MVT::i64, Ops);
+  return true;
+}
+
 bool PPCDAGToDAGISel::tryAsSingleRLWIMI(SDNode *N) {
   assert(N->getOpcode() == ISD::AND && "ISD::AND SDNode expected");
   unsigned Imm;
   if (!isInt32Immediate(N->getOperand(1), Imm))
     return false;
 
   SDValue Val = N->getOperand(0);
   unsigned Imm2;
if (Offset.getOpcode() == ISD::TargetConstant ||
       ReplaceNode(N, MN);
       return;
     }
   }
 
   case ISD::AND:
     // If this is an 'and' with a mask, try to emit rlwinm/rldicl/rldicr
     if (tryAsSingleRLWINM(N) || tryAsSingleRLWIMI(N) || tryAsSingleRLDICL(N) ||
-        tryAsSingleRLDICR(N) || tryAsSingleRLWINM8(N) || tryAsPairOfRLDICL(N))
+        tryAsSingleRLDICR(N) || tryAsSingleRLWINM8(N) || tryAsPairOfRLDICL(N) ||
+        tryAsPairOfRLWINM8(N))
       return;
 
     // Other cases are autogenerated.
     break;
   case ISD::OR: {
     if (N->getValueType(0) == MVT::i32)
       if (tryBitfieldInsert(N))
         return;

llvm/test/CodeGen/PowerPC/and-mask.ll

; CHECK-NEXT:    blr
   %and = and i64 %a, 4290838527
   ret i64 %and
 }
 
 ; mask: 0x3FC0FFE0
 define i64 @test6(i64 %a) {
 ; CHECK-LABEL: test6:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    lis 4, 16320
-; CHECK-NEXT:    ori 4, 4, 65504
-; CHECK-NEXT:    and 3, 3, 4
+; CHECK-NEXT:    rlwinm 3, 3, 0, 16, 9
+; CHECK-NEXT:    rlwinm 3, 3, 0, 2, 26
 ; CHECK-NEXT:    blr
   %and = and i64 %a, 1069613024
   ret i64 %and
 }
 
 ; mask: 0x3FC000001FFFF
 define i64 @test7(i64 %a) {
 ; CHECK-LABEL: test7:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    rldicl 3, 3, 22, 25
 ; CHECK-NEXT:    rldicl 3, 3, 42, 14
 ; CHECK-NEXT:    blr
   %and = and i64 %a, 1121501860462591
   ret i64 %and
 }