[SystemZ] Add a mapping from "select register" to "load on condition" (2-addr).

The SELR(Mux) instructions can be converted to two-address form as LOCR(Mux)
instructions whenever one of the sources are the same reg as dest. By adding
this mapping in getTwoOperandOpcode(), we get:

- Two-address hints in getRegAllocationHints() for select register
  instructions.

- No need anymore for special handling in SystemZShortenInst.cpp -
  shortenSelect() removed.

The two-address hints are now added before the GRX32 hints, which should be
preferred.

Review: Ulrich Weigand
https://reviews.llvm.org/D68870

4 files changed, 60 insertions, 81 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZInstrFormats.td b/llvm/lib/Target/SystemZ/SystemZInstrFormats.td
index ba87ddb20f9..f064d33ac2f 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrFormats.td
+++ b/llvm/lib/Target/SystemZ/SystemZInstrFormats.td
@@ -3209,6 +3209,8 @@ class CondBinaryRRF<string mnemonic, bits<16> opcode, RegisterOperand cls1,
   let Constraints = "$R1 = $R1src";
   let DisableEncoding = "$R1src";
   let CCMaskLast = 1;
+  let NumOpsKey = !subst("loc", "sel", mnemonic);
+  let NumOpsValue = "2";
 }
 
 // Like CondBinaryRRF, but used for the raw assembly form.  The condition-code
@@ -3248,6 +3250,8 @@ class CondBinaryRRFa<string mnemonic, bits<16> opcode, RegisterOperand cls1,
              [(set cls1:$R1, (z_select_ccmask cls2:$R2, cls3:$R3,
                                               cond4:$valid, cond4:$M4))]> {
   let CCMaskLast = 1;
+  let NumOpsKey = mnemonic;
+  let NumOpsValue = "3";
 }
 
 // Like CondBinaryRRFa, but used for the raw assembly form.  The condition-code
@@ -4798,7 +4802,8 @@ class TestBinarySILPseudo<SDPatternOperator operator, ImmOpWithPattern imm>
 
 // Like CondBinaryRRF, but expanded after RA depending on the choice of
 // register.
-class CondBinaryRRFPseudo<RegisterOperand cls1, RegisterOperand cls2>
+class CondBinaryRRFPseudo<string mnemonic, RegisterOperand cls1,
+                          RegisterOperand cls2>
   : Pseudo<(outs cls1:$R1),
            (ins cls1:$R1src, cls2:$R2, cond4:$valid, cond4:$M3),
            [(set cls1:$R1, (z_select_ccmask cls2:$R2, cls1:$R1src,
@@ -4806,17 +4811,21 @@ class CondBinaryRRFPseudo<RegisterOperand cls1, RegisterOperand cls2>
   let Constraints = "$R1 = $R1src";
   let DisableEncoding = "$R1src";
   let CCMaskLast = 1;
+  let NumOpsKey = !subst("loc", "sel", mnemonic);
+  let NumOpsValue = "2";
 }
 
 // Like CondBinaryRRFa, but expanded after RA depending on the choice of
 // register.
-class CondBinaryRRFaPseudo<RegisterOperand cls1, RegisterOperand cls2,
-                           RegisterOperand cls3>
+class CondBinaryRRFaPseudo<string mnemonic, RegisterOperand cls1,
+                           RegisterOperand cls2, RegisterOperand cls3>
   : Pseudo<(outs cls1:$R1),
            (ins cls3:$R3, cls2:$R2, cond4:$valid, cond4:$M4),
            [(set cls1:$R1, (z_select_ccmask cls2:$R2, cls3:$R3,
                                             cond4:$valid, cond4:$M4))]> {
   let CCMaskLast = 1;
+  let NumOpsKey = mnemonic;
+  let NumOpsValue = "3";
 }
 
 // Like CondBinaryRIE, but expanded after RA depending on the choice of
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.td b/llvm/lib/Target/SystemZ/SystemZInstrInfo.td
index aa981e718b5..9579dcc0d1b 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.td
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.td
@@ -492,7 +492,7 @@ let Predicates = [FeatureMiscellaneousExtensions3], Uses = [CC] in {
   let isCommutable = 1 in {
     // Expands to SELR or SELFHR or a branch-and-move sequence,
     // depending on the choice of registers.
-    def  SELRMux : CondBinaryRRFaPseudo<GRX32, GRX32, GRX32>;
+    def  SELRMux : CondBinaryRRFaPseudo<"selrmux", GRX32, GRX32, GRX32>;
     defm SELFHR  : CondBinaryRRFaPair<"selfhr", 0xB9C0, GRH32, GRH32, GRH32>;
     defm SELR    : CondBinaryRRFaPair<"selr",   0xB9F0, GR32, GR32, GR32>;
     defm SELGR   : CondBinaryRRFaPair<"selgr",  0xB9E3, GR64, GR64, GR64>;
@@ -525,7 +525,7 @@ let Predicates = [FeatureLoadStoreOnCond2], Uses = [CC] in {
   let isCommutable = 1 in {
     // Expands to LOCR or LOCFHR or a branch-and-move sequence,
     // depending on the choice of registers.
-    def LOCRMux : CondBinaryRRFPseudo<GRX32, GRX32>;
+    def LOCRMux : CondBinaryRRFPseudo<"locrmux", GRX32, GRX32>;
     defm LOCFHR : CondBinaryRRFPair<"locfhr", 0xB9E0, GRH32, GRH32>;
   }
 
diff --git a/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp b/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
index cbcfc07f2b1..0d5e7af9252 100644
--- a/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
@@ -87,6 +87,52 @@ SystemZRegisterInfo::getRegAllocationHints(unsigned VirtReg,
   bool BaseImplRetVal = TargetRegisterInfo::getRegAllocationHints(
       VirtReg, Order, Hints, MF, VRM, Matrix);
 
+  if (VRM != nullptr) {
+    // Add any two address hints after any copy hints.
+    SmallSet<unsigned, 4> TwoAddrHints;
+    for (auto &Use : MRI->reg_nodbg_instructions(VirtReg))
+      if (SystemZ::getTwoOperandOpcode(Use.getOpcode()) != -1) {
+        const MachineOperand *VRRegMO = nullptr;
+        const MachineOperand *OtherMO = nullptr;
+        const MachineOperand *CommuMO = nullptr;
+        if (VirtReg == Use.getOperand(0).getReg()) {
+          VRRegMO = &Use.getOperand(0);
+          OtherMO = &Use.getOperand(1);
+          if (Use.isCommutable())
+            CommuMO = &Use.getOperand(2);
+        } else if (VirtReg == Use.getOperand(1).getReg()) {
+          VRRegMO = &Use.getOperand(1);
+          OtherMO = &Use.getOperand(0);
+        } else if (VirtReg == Use.getOperand(2).getReg() &&
+                   Use.isCommutable()) {
+          VRRegMO = &Use.getOperand(2);
+          OtherMO = &Use.getOperand(0);
+        } else
+          continue;
+
+        auto tryAddHint = [&](const MachineOperand *MO) -> void {
+          Register Reg = MO->getReg();
+          Register PhysReg =
+            Register::isPhysicalRegister(Reg) ? Reg : VRM->getPhys(Reg);
+          if (PhysReg) {
+            if (MO->getSubReg())
+              PhysReg = getSubReg(PhysReg, MO->getSubReg());
+            if (VRRegMO->getSubReg())
+              PhysReg = getMatchingSuperReg(PhysReg, VRRegMO->getSubReg(),
+                                            MRI->getRegClass(VirtReg));
+            if (!MRI->isReserved(PhysReg) && !is_contained(Hints, PhysReg))
+              TwoAddrHints.insert(PhysReg);
+          }
+        };
+        tryAddHint(OtherMO);
+        if (CommuMO)
+          tryAddHint(CommuMO);
+      }
+    for (MCPhysReg OrderReg : Order)
+      if (TwoAddrHints.count(OrderReg))
+        Hints.push_back(OrderReg);
+  }
+
   if (MRI->getRegClass(VirtReg) == &SystemZ::GRX32BitRegClass) {
     SmallVector<unsigned, 8> Worklist;
     SmallSet<unsigned, 4> DoneRegs;
@@ -143,52 +189,6 @@ SystemZRegisterInfo::getRegAllocationHints(unsigned VirtReg,
     }
   }
 
-  if (VRM == nullptr)
-    return BaseImplRetVal;
-
-  // Add any two address hints after any copy hints.
-  SmallSet<unsigned, 4> TwoAddrHints;
-  for (auto &Use : MRI->reg_nodbg_instructions(VirtReg))
-    if (SystemZ::getTwoOperandOpcode(Use.getOpcode()) != -1) {
-      const MachineOperand *VRRegMO = nullptr;
-      const MachineOperand *OtherMO = nullptr;
-      const MachineOperand *CommuMO = nullptr;
-      if (VirtReg == Use.getOperand(0).getReg()) {
-        VRRegMO = &Use.getOperand(0);
-        OtherMO = &Use.getOperand(1);
-        if (Use.isCommutable())
-          CommuMO = &Use.getOperand(2);
-      } else if (VirtReg == Use.getOperand(1).getReg()) {
-        VRRegMO = &Use.getOperand(1);
-        OtherMO = &Use.getOperand(0);
-      } else if (VirtReg == Use.getOperand(2).getReg() && Use.isCommutable()) {
-        VRRegMO = &Use.getOperand(2);
-        OtherMO = &Use.getOperand(0);
-      } else
-        continue;
-
-      auto tryAddHint = [&](const MachineOperand *MO) -> void {
-        Register Reg = MO->getReg();
-        Register PhysReg =
-            Register::isPhysicalRegister(Reg) ? Reg : VRM->getPhys(Reg);
-        if (PhysReg) {
-          if (MO->getSubReg())
-            PhysReg = getSubReg(PhysReg, MO->getSubReg());
-          if (VRRegMO->getSubReg())
-            PhysReg = getMatchingSuperReg(PhysReg, VRRegMO->getSubReg(),
-                                          MRI->getRegClass(VirtReg));
-          if (!MRI->isReserved(PhysReg) && !is_contained(Hints, PhysReg))
-            TwoAddrHints.insert(PhysReg);
-        }
-      };
-      tryAddHint(OtherMO);
-      if (CommuMO)
-        tryAddHint(CommuMO);
-    }
-  for (MCPhysReg OrderReg : Order)
-    if (TwoAddrHints.count(OrderReg))
-      Hints.push_back(OrderReg);
-
   return BaseImplRetVal;
 }
 
diff --git a/llvm/lib/Target/SystemZ/SystemZShortenInst.cpp b/llvm/lib/Target/SystemZ/SystemZShortenInst.cpp
index 1b9c8ea2759..f6184cec795 100644
--- a/llvm/lib/Target/SystemZ/SystemZShortenInst.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZShortenInst.cpp
@@ -46,7 +46,6 @@ private:
   bool shortenOn001(MachineInstr &MI, unsigned Opcode);
   bool shortenOn001AddCC(MachineInstr &MI, unsigned Opcode);
   bool shortenFPConv(MachineInstr &MI, unsigned Opcode);
-  bool shortenSelect(MachineInstr &MI, unsigned Opcode);
 
   const SystemZInstrInfo *TII;
   const TargetRegisterInfo *TRI;
@@ -176,23 +175,6 @@ bool SystemZShortenInst::shortenFPConv(MachineInstr &MI, unsigned Opcode) {
   return false;
 }
 
-// MI is a three-operand select instruction.  If one of the sources match
-// the destination, convert to the equivalent load-on-condition.
-bool SystemZShortenInst::shortenSelect(MachineInstr &MI, unsigned Opcode) {
-  if (MI.getOperand(0).getReg() == MI.getOperand(1).getReg()) {
-    MI.setDesc(TII->get(Opcode));
-    MI.tieOperands(0, 1);
-    return true;
-  }
-  if (MI.getOperand(0).getReg() == MI.getOperand(2).getReg()) {
-    TII->commuteInstruction(MI, false, 1, 2);
-    MI.setDesc(TII->get(Opcode));
-    MI.tieOperands(0, 1);
-    return true;
-  }
-  return false;
-}
-
 // Process all instructions in MBB.  Return true if something changed.
 bool SystemZShortenInst::processBlock(MachineBasicBlock &MBB) {
   bool Changed = false;
@@ -213,18 +195,6 @@ bool SystemZShortenInst::processBlock(MachineBasicBlock &MBB) {
       Changed |= shortenIIF(MI, SystemZ::LLIHL, SystemZ::LLIHH);
       break;
 
-    case SystemZ::SELR:
-      Changed |= shortenSelect(MI, SystemZ::LOCR);
-      break;
-
-    case SystemZ::SELFHR:
-      Changed |= shortenSelect(MI, SystemZ::LOCFHR);
-      break;
-
-    case SystemZ::SELGR:
-      Changed |= shortenSelect(MI, SystemZ::LOCGR);
-      break;
-
     case SystemZ::WFADB:
       Changed |= shortenOn001AddCC(MI, SystemZ::ADBR);
       break;