[AMDGPU] Allow SDWA in instructions with immediates and SGPRs

An encoding does not allow to use SDWA in an instruction with
scalar operands, either literals or SGPRs. That is however possible
to copy these operands into a VGPR first.

Several copies of the value are produced if multiple SDWA conversions
were done. To cleanup MachineLICM (to hoist copies out of loops),
MachineCSE (to remove duplicate copies) and SIFoldOperands (to replace
SGPR to VGPR copy with immediate copy right to the VGPR) runs are added
after the SDWA pass.

Differential Revision: https://reviews.llvm.org/D33583

llvm-svn: 304219

1 files changed, 35 insertions, 14 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp b/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp
index 4dc090d9b7e..fae249b0449 100644
--- a/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp
+++ b/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp
@@ -55,6 +55,7 @@ private:
 
   std::unordered_map<MachineInstr *, std::unique_ptr<SDWAOperand>> SDWAOperands;
   std::unordered_map<MachineInstr *, SDWAOperandsVector> PotentialMatches;
+  SmallVector<MachineInstr *, 8> ConvertedInstructions;
 
   Optional<int64_t> foldToImm(const MachineOperand &Op) const;
 
@@ -69,6 +70,7 @@ public:
   void matchSDWAOperands(MachineFunction &MF);
   bool isConvertibleToSDWA(const MachineInstr &MI) const;
   bool convertToSDWA(MachineInstr &MI, const SDWAOperandsVector &SDWAOperands);
+  void legalizeScalarOperands(MachineInstr &MI) const;
 
   StringRef getPassName() const override { return "SI Peephole SDWA"; }
 
@@ -289,7 +291,7 @@ bool SDWASrcOperand::convertToSDWA(MachineInstr &MI, const SIInstrInfo *TII) {
   MachineOperand *SrcSel = TII->getNamedOperand(MI, AMDGPU::OpName::src0_sel);
   MachineOperand *SrcMods =
       TII->getNamedOperand(MI, AMDGPU::OpName::src0_modifiers);
-  assert(Src && Src->isReg());
+  assert(Src && (Src->isReg() || Src->isImm()));
   if (!isSameReg(*Src, *getReplacedOperand())) {
     // If this is not src0 then it should be src1
     Src = TII->getNamedOperand(MI, AMDGPU::OpName::src1);
@@ -580,18 +582,8 @@ void SIPeepholeSDWA::matchSDWAOperands(MachineFunction &MF) {
 }
 
 bool SIPeepholeSDWA::isConvertibleToSDWA(const MachineInstr &MI) const {
-  // Check if this instruction can be converted to SDWA:
-  // 1. Does this opcode support SDWA
-  if (AMDGPU::getSDWAOp(MI.getOpcode()) == -1)
-    return false;
-
-  // 2. Are all operands - VGPRs
-  for (const MachineOperand &Operand : MI.explicit_operands()) {
-    if (!Operand.isReg() || !TRI->isVGPR(*MRI, Operand.getReg()))
-      return false;
-  }
-
-  return true;
+  // Check if this instruction has opcode that supports SDWA
+  return AMDGPU::getSDWAOp(MI.getOpcode()) != -1;
 }
 
 bool SIPeepholeSDWA::convertToSDWA(MachineInstr &MI,
@@ -685,7 +677,9 @@ bool SIPeepholeSDWA::convertToSDWA(MachineInstr &MI,
     if (PotentialMatches.count(Operand->getParentInst()) == 0)
       Converted |= Operand->convertToSDWA(*SDWAInst, TII);
   }
-  if (!Converted) {
+  if (Converted) {
+    ConvertedInstructions.push_back(SDWAInst);
+  } else {
     SDWAInst->eraseFromParent();
     return false;
   }
@@ -698,6 +692,29 @@ bool SIPeepholeSDWA::convertToSDWA(MachineInstr &MI,
   return true;
 }
 
+// If an instruction was converted to SDWA it should not have immediates or SGPR
+// operands. Copy its scalar operands into VGPRs.
+void SIPeepholeSDWA::legalizeScalarOperands(MachineInstr &MI) const {
+  const MCInstrDesc &Desc = TII->get(MI.getOpcode());
+  for (unsigned I = 0, E = MI.getNumExplicitOperands(); I != E; ++I) {
+    MachineOperand &Op = MI.getOperand(I);
+    if (!Op.isImm() && !(Op.isReg() && !TRI->isVGPR(*MRI, Op.getReg())))
+      continue;
+    if (Desc.OpInfo[I].RegClass == -1 ||
+       !TRI->hasVGPRs(TRI->getRegClass(Desc.OpInfo[I].RegClass)))
+      continue;
+    unsigned VGPR = MRI->createVirtualRegister(&AMDGPU::VGPR_32RegClass);
+    auto Copy = BuildMI(*MI.getParent(), MI.getIterator(), MI.getDebugLoc(),
+                        TII->get(AMDGPU::V_MOV_B32_e32), VGPR);
+    if (Op.isImm())
+      Copy.addImm(Op.getImm());
+    else if (Op.isReg())
+      Copy.addReg(Op.getReg(), Op.isKill() ? RegState::Kill : 0,
+                  Op.getSubReg());
+    Op.ChangeToRegister(VGPR, false);
+  }
+}
+
 bool SIPeepholeSDWA::runOnMachineFunction(MachineFunction &MF) {
   const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
 
@@ -728,5 +745,9 @@ bool SIPeepholeSDWA::runOnMachineFunction(MachineFunction &MF) {
 
   PotentialMatches.clear();
   SDWAOperands.clear();
+
+  while (!ConvertedInstructions.empty())
+    legalizeScalarOperands(*ConvertedInstructions.pop_back_val());
+
   return false;
 }