AMDGPU/GlobalISel: Add selectVOP3Mods_nnan

[arsenm]

Summary

This doesn't enable any new imports yet, but moves the fmed patterns
from failing on this to hitting the "complex suboperand referenced
more than once" limitation in tablegen.

[nhaehnle]

LGTM

[arsenm]

79450a4ea26a0e9731eaf2629f6dd8c1ffd8f407

llvm/lib/Target/AMDGPU/AMDGPUGISel.td

 def gi_vop3mods0 :
     GIComplexOperandMatcher<s32, "selectVOP3Mods0">,
     GIComplexPatternEquiv<VOP3Mods0>;
 
 def gi_vop3mods :
     GIComplexOperandMatcher<s32, "selectVOP3Mods">,
     GIComplexPatternEquiv<VOP3Mods>;
 
+def gi_vop3mods_nnan :
+    GIComplexOperandMatcher<s32, "selectVOP3Mods_nnan">,
+    GIComplexPatternEquiv<VOP3Mods_nnan>;
+
 def gi_vop3omods :
     GIComplexOperandMatcher<s32, "selectVOP3OMods">,
     GIComplexPatternEquiv<VOP3OMods>;
 
 def gi_vop3opselmods0 :
     GIComplexOperandMatcher<s32, "selectVOP3OpSelMods0">,
     GIComplexPatternEquiv<VOP3OpSelMods0>;
 

llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.h

private:
   selectVSRC0(MachineOperand &Root) const;
 
   InstructionSelector::ComplexRendererFns
   selectVOP3Mods0(MachineOperand &Root) const;
   InstructionSelector::ComplexRendererFns
   selectVOP3OMods(MachineOperand &Root) const;
   InstructionSelector::ComplexRendererFns
   selectVOP3Mods(MachineOperand &Root) const;
+  InstructionSelector::ComplexRendererFns
+  selectVOP3Mods_nnan(MachineOperand &Root) const;
 
   InstructionSelector::ComplexRendererFns
   selectVOP3OpSelMods0(MachineOperand &Root) const;
   InstructionSelector::ComplexRendererFns
   selectVOP3OpSelMods(MachineOperand &Root) const;
 
   InstructionSelector::ComplexRendererFns
   selectSmrdImm(MachineOperand &Root) const;

llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp

AMDGPUInstructionSelector::selectVOP3Mods(MachineOperand &Root) const {
 
   return {{
       [=](MachineInstrBuilder &MIB) { MIB.addReg(Src); },
       [=](MachineInstrBuilder &MIB) { MIB.addImm(Mods); }  // src_mods
   }};
 }
 
 InstructionSelector::ComplexRendererFns
+AMDGPUInstructionSelector::selectVOP3Mods_nnan(MachineOperand &Root) const {
+  Register Src;
+  unsigned Mods;
+  std::tie(Src, Mods) = selectVOP3ModsImpl(Root.getReg());
+  if (!TM.Options.NoNaNsFPMath && !isKnownNeverNaN(Src, *MRI))
+    return None;
+
+  return {{
+      [=](MachineInstrBuilder &MIB) { MIB.addReg(Src); },
+      [=](MachineInstrBuilder &MIB) { MIB.addImm(Mods); }  // src_mods
+  }};
+}
+
+InstructionSelector::ComplexRendererFns
 AMDGPUInstructionSelector::selectVOP3OpSelMods0(MachineOperand &Root) const {
   // FIXME: Handle clamp and op_sel
   return {{
       [=](MachineInstrBuilder &MIB) { MIB.addReg(Root.getReg()); },
       [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }, // src_mods
       [=](MachineInstrBuilder &MIB) { MIB.addImm(0); }  // clamp
   }};
 }