[AMDGPU] Serialize WWM_REG vreg flag

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -1718,6 +1718,17 @@ bool GCNTargetMachine::parseMachineFunctionInfo(
     MFI->reserveWWMRegister(ParsedReg);
   }
 
+  for (const auto &[_, Info] : PFS.VRegInfosNamed) {
+    for (uint8_t Flag : Info->Flags) {
+      MFI->setFlag(Info->VReg, Flag);
+    }
+  }
+  for (const auto &[_, Info] : PFS.VRegInfos) {
+    for (uint8_t Flag : Info->Flags) {
+      MFI->setFlag(Info->VReg, Flag);
+    }
+  }
+
   auto parseAndCheckArgument = [&](const std::optional<yaml::SIArgument> &A,
                                    const TargetRegisterClass &RC,
                                    ArgDescriptor &Arg, unsigned UserSGPRs,

llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp

@@ -3851,3 +3851,13 @@ SIRegisterInfo::getSubRegAlignmentNumBits(const TargetRegisterClass *RC,
   }
   return 0;
 }
+
+SmallVector<StringLiteral>
+SIRegisterInfo::getVRegFlagsOfReg(Register Reg,
+                                  const MachineFunction &MF) const {
+  SmallVector<StringLiteral> RegFlags;
+  const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
+  if (FuncInfo->checkFlag(Reg, AMDGPU::VirtRegFlag::WWM_REG))
+    RegFlags.push_back("WWM_REG");
+  return RegFlags;
+}

llvm/lib/Target/AMDGPU/SIRegisterInfo.h

@@ -457,6 +457,14 @@ class SIRegisterInfo final : public AMDGPUGenRegisterInfo {
   // No check if the subreg is supported by the current RC is made.
   unsigned getSubRegAlignmentNumBits(const TargetRegisterClass *RC,
                                      unsigned SubReg) const;
+
+  std::optional<uint8_t> getVRegFlagValue(StringRef Name) const override {
+    return Name == "WWM_REG" ? AMDGPU::VirtRegFlag::WWM_REG
+                             : std::optional<uint8_t>{};
+  }
+
+  SmallVector<StringLiteral>
+  getVRegFlagsOfReg(Register Reg, const MachineFunction &MF) const override;
 };
 
 namespace AMDGPU {

llvm/test/CodeGen/MIR/AMDGPU/machine-function-info-no-ir.mir

@@ -578,3 +578,18 @@ body:             |
     SI_RETURN
 
 ...
+---
+name: vregs
+# FULL: registers:
+# FULL-NEXT:   - { id: 0, class: vgpr_32, preferred-register: '$vgpr1', flags: [ WWM_REG ] }
+# FULL-NEXT:   - { id: 1, class: sgpr_64, preferred-register: '$sgpr0_sgpr1', flags: [  ] }
+# FULL-NEXT:   - { id: 2, class: sgpr_64, preferred-register: '', flags: [  ] }
+registers:
+  - { id: 0, class: vgpr_32, preferred-register: $vgpr1, flags: [ WWM_REG ]}
+  - { id: 1, class: sgpr_64, preferred-register: $sgpr0_sgpr1 }
+  - { id: 2, class: sgpr_64, flags: [ ] }
+body: |
+  bb.0:
+    %2:sgpr_64 = COPY %1
+    %1:sgpr_64 = COPY %0
+...