llvm · rampitec · Sep 4, 2025 · Sep 4, 2025
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUInstPrinter.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUInstPrinter.cpp
@@ -336,6 +336,42 @@ static MCPhysReg getRegForPrinting(MCPhysReg Reg, const MCRegisterInfo &MRI) {
   return RC->getRegister(Idx % 0x100);
 }
 
+// Restore MSBs of a VGPR above 255 from the MCInstrAnalysis.
+static MCPhysReg getRegFromMIA(MCPhysReg Reg, unsigned OpNo,
+                               const MCInstrDesc &Desc,
+                               const MCRegisterInfo &MRI,
+                               const AMDGPUMCInstrAnalysis &MIA) {
+  unsigned VgprMSBs = MIA.getVgprMSBs();
+  if (!VgprMSBs)
+    return Reg;
+
+  unsigned Enc = MRI.getEncodingValue(Reg);
+  if (!(Enc & AMDGPU::HWEncoding::IS_VGPR))
+    return Reg;
+
+  auto Ops = AMDGPU::getVGPRLoweringOperandTables(Desc);
+  if (!Ops.first)
+    return Reg;
+  unsigned Opc = Desc.getOpcode();
+  unsigned I;
+  for (I = 0; I < 4; ++I) {
+    if (Ops.first[I] != AMDGPU::OpName::NUM_OPERAND_NAMES &&
+        (unsigned)AMDGPU::getNamedOperandIdx(Opc, Ops.first[I]) == OpNo)
+      break;
+    if (Ops.second && Ops.second[I] != AMDGPU::OpName::NUM_OPERAND_NAMES &&
+        (unsigned)AMDGPU::getNamedOperandIdx(Opc, Ops.second[I]) == OpNo)
+      break;
+  }
+  if (I == 4)
+    return Reg;
+  unsigned OpMSBs = (VgprMSBs >> (I * 2)) & 3;
+  if (!OpMSBs)
+    return Reg;
+  if (MCRegister NewReg = AMDGPU::getVGPRWithMSBs(Reg, OpMSBs, MRI))
+    return NewReg;
+  return Reg;
+}
+
 void AMDGPUInstPrinter::printRegOperand(MCRegister Reg, raw_ostream &O,
                                         const MCRegisterInfo &MRI) {
 #if !defined(NDEBUG)
@@ -359,6 +395,9 @@ void AMDGPUInstPrinter::printRegOperand(MCRegister Reg, raw_ostream &O,
 void AMDGPUInstPrinter::printRegOperand(MCRegister Reg, unsigned Opc,
                                         unsigned OpNo, raw_ostream &O,
                                         const MCRegisterInfo &MRI) {
+  if (MIA)
+    Reg = getRegFromMIA(Reg, OpNo, MII.get(Opc), MRI,
+                        *static_cast<const AMDGPUMCInstrAnalysis *>(MIA));
   printRegOperand(Reg, O, MRI);
 }
 

diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
@@ -21,9 +21,9 @@
 #include "TargetInfo/AMDGPUTargetInfo.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCInstPrinter.h"
-#include "llvm/MC/MCInstrAnalysis.h"
 #include "llvm/MC/MCInstrDesc.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCObjectWriter.h"
@@ -130,31 +130,35 @@ static MCStreamer *createMCStreamer(const Triple &T, MCContext &Context,
                                  std::move(Emitter));
 }
 
-namespace {
-
-class AMDGPUMCInstrAnalysis : public MCInstrAnalysis {
-public:
-  explicit AMDGPUMCInstrAnalysis(const MCInstrInfo *Info)
-      : MCInstrAnalysis(Info) {}
-
-  bool evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
-                      uint64_t &Target) const override {
-    if (Inst.getNumOperands() == 0 || !Inst.getOperand(0).isImm() ||
-        Info->get(Inst.getOpcode()).operands()[0].OperandType !=
-            MCOI::OPERAND_PCREL)
-      return false;
+namespace llvm {
+namespace AMDGPU {
+
+bool AMDGPUMCInstrAnalysis::evaluateBranch(const MCInst &Inst, uint64_t Addr,
+                                           uint64_t Size,
+                                           uint64_t &Target) const {
+  if (Inst.getNumOperands() == 0 || !Inst.getOperand(0).isImm() ||
+      Info->get(Inst.getOpcode()).operands()[0].OperandType !=
+          MCOI::OPERAND_PCREL)
+    return false;
+
+  int64_t Imm = Inst.getOperand(0).getImm();
+  // Our branches take a simm16.
+  Target = SignExtend64<16>(Imm) * 4 + Addr + Size;
+  return true;
+}
 
-    int64_t Imm = Inst.getOperand(0).getImm();
-    // Our branches take a simm16.
-    Target = SignExtend64<16>(Imm) * 4 + Addr + Size;
-    return true;
-  }
-};
+void AMDGPUMCInstrAnalysis::updateState(const MCInst &Inst, uint64_t Addr) {
+  if (Inst.getOpcode() == AMDGPU::S_SET_VGPR_MSB_gfx12)
+    VgprMSBs = Inst.getOperand(0).getImm();
+  else if (isTerminator(Inst))
+    VgprMSBs = 0;
+}
 
-} // end anonymous namespace
+} // end namespace AMDGPU
+} // end namespace llvm
 
 static MCInstrAnalysis *createAMDGPUMCInstrAnalysis(const MCInstrInfo *Info) {
-  return new AMDGPUMCInstrAnalysis(Info);
+  return new AMDGPU::AMDGPUMCInstrAnalysis(Info);
 }
 
 extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void

diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.h b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.h
@@ -15,6 +15,7 @@
 #ifndef LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCTARGETDESC_H
 #define LLVM_LIB_TARGET_AMDGPU_MCTARGETDESC_AMDGPUMCTARGETDESC_H
 
+#include "llvm/MC/MCInstrAnalysis.h"
 #include <cstdint>
 #include <memory>
 
@@ -44,6 +45,28 @@ MCAsmBackend *createAMDGPUAsmBackend(const Target &T,
 std::unique_ptr<MCObjectTargetWriter>
 createAMDGPUELFObjectWriter(bool Is64Bit, uint8_t OSABI,
                             bool HasRelocationAddend);
+
+namespace AMDGPU {
+class AMDGPUMCInstrAnalysis : public MCInstrAnalysis {
+private:
+  unsigned VgprMSBs = 0;
+
+public:
+  explicit AMDGPUMCInstrAnalysis(const MCInstrInfo *Info)
+      : MCInstrAnalysis(Info) {}
+
+  bool evaluateBranch(const MCInst &Inst, uint64_t Addr, uint64_t Size,
+                      uint64_t &Target) const override;
+
+  void resetState() override { VgprMSBs = 0; }
+
+  void updateState(const MCInst &Inst, uint64_t Addr) override;
+
+  unsigned getVgprMSBs() const { return VgprMSBs; }
+};
+
+} // namespace AMDGPU
+
 } // namespace llvm
 
 #define GET_REGINFO_ENUM

diff --git a/llvm/test/CodeGen/AMDGPU/vgpr-lowering-gfx1250.mir b/llvm/test/CodeGen/AMDGPU/vgpr-lowering-gfx1250.mir
@@ -1,4 +1,5 @@
 # RUN: llc -mtriple=amdgcn -mcpu=gfx1250 -start-before=amdgpu-lower-vgpr-encoding -o - %s | FileCheck -check-prefixes=GCN,ASM %s
+# RUN: llc -mtriple=amdgcn -mcpu=gfx1250 -start-before=amdgpu-lower-vgpr-encoding -o - %s | llvm-mc -triple=amdgcn -mcpu=gfx1250 -filetype=obj -o - | llvm-objdump -d --mcpu=gfx1250 - | FileCheck -check-prefixes=GCN,DIS %s
 
 # ASM-LABEL: {{^}}high_vgprs:
 # DIS-LABEL: <high_vgprs>: