AMDGPU: Prepare for explicit absolute relocations in code generation

[nhaehnle]

Summary

We will use absolute relocations for LDS symbols.

Change-Id: I9a32795ed0ea835e433a787129cfe3c57ee9a325

[arsenm]

lib/Target/AMDGPU/SIInstrInfo.cpp

5536–5538

Should add tests in test/CodeGen/MIR/AMDGPU

[nhaehnle]

Add a test/CodeGen/MIR/AMDGPU test.

[nhaehnle]

ping?

[arsenm]

LGTM with nit

lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp

381–384

return Kind != lo && Kind != Hi

[nhaehnle]

lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp

381–384

Yeah, that makes sense. Thanks!

include/llvm/MC/MCExpr.h

enum VariantKind : uint16_t {
     VK_WASM_MBREL,     // Memory address relative to memory base
     VK_WASM_TBREL,     // Table index relative to table bare
 
     VK_AMDGPU_GOTPCREL32_LO, // symbol@gotpcrel32@lo
     VK_AMDGPU_GOTPCREL32_HI, // symbol@gotpcrel32@hi
     VK_AMDGPU_REL32_LO,      // symbol@rel32@lo
     VK_AMDGPU_REL32_HI,      // symbol@rel32@hi
     VK_AMDGPU_REL64,         // symbol@rel64
+    VK_AMDGPU_ABS32_LO,      // symbol@abs32@lo
+    VK_AMDGPU_ABS32_HI,      // symbol@abs32@hi
 
     VK_TPREL,
     VK_DTPREL
   };
 
 private:
   /// The symbol reference modifier.
   const VariantKind Kind;

lib/MC/MCExpr.cpp

StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
   case VK_WASM_TYPEINDEX: return "TYPEINDEX";
   case VK_WASM_MBREL: return "MBREL";
   case VK_WASM_TBREL: return "TBREL";
   case VK_AMDGPU_GOTPCREL32_LO: return "gotpcrel32@lo";
   case VK_AMDGPU_GOTPCREL32_HI: return "gotpcrel32@hi";
   case VK_AMDGPU_REL32_LO: return "rel32@lo";
   case VK_AMDGPU_REL32_HI: return "rel32@hi";
   case VK_AMDGPU_REL64: return "rel64";
+  case VK_AMDGPU_ABS32_LO: return "abs32@lo";
+  case VK_AMDGPU_ABS32_HI: return "abs32@hi";
   }
   llvm_unreachable("Invalid variant kind");
 }
 
 MCSymbolRefExpr::VariantKind
 MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
   return StringSwitch<VariantKind>(Name.lower())
     .Case("dtprel", VK_DTPREL)
return StringSwitch<VariantKind>(Name.lower())
     .Case("typeindex", VK_WASM_TYPEINDEX)
     .Case("tbrel", VK_WASM_TBREL)
     .Case("mbrel", VK_WASM_MBREL)
     .Case("gotpcrel32@lo", VK_AMDGPU_GOTPCREL32_LO)
     .Case("gotpcrel32@hi", VK_AMDGPU_GOTPCREL32_HI)
     .Case("rel32@lo", VK_AMDGPU_REL32_LO)
     .Case("rel32@hi", VK_AMDGPU_REL32_HI)
     .Case("rel64", VK_AMDGPU_REL64)
+    .Case("abs32@lo", VK_AMDGPU_ABS32_LO)
+    .Case("abs32@hi", VK_AMDGPU_ABS32_HI)
     .Default(VK_Invalid);
 }
 
 void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const {
   if (UseParensForSymbolVariant)
     OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')';
   else
     OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind());

lib/Target/AMDGPU/AMDGPUMCInstLower.cpp

static MCSymbolRefExpr::VariantKind getVariantKind(unsigned MOFlags) {
   case SIInstrInfo::MO_GOTPCREL32_LO:
     return MCSymbolRefExpr::VK_AMDGPU_GOTPCREL32_LO;
   case SIInstrInfo::MO_GOTPCREL32_HI:
     return MCSymbolRefExpr::VK_AMDGPU_GOTPCREL32_HI;
   case SIInstrInfo::MO_REL32_LO:
     return MCSymbolRefExpr::VK_AMDGPU_REL32_LO;
   case SIInstrInfo::MO_REL32_HI:
     return MCSymbolRefExpr::VK_AMDGPU_REL32_HI;
+  case SIInstrInfo::MO_ABS32_LO:
+    return MCSymbolRefExpr::VK_AMDGPU_ABS32_LO;
+  case SIInstrInfo::MO_ABS32_HI:
+    return MCSymbolRefExpr::VK_AMDGPU_ABS32_HI;
   }
 }
 
 const MCExpr *AMDGPUMCInstLower::getLongBranchBlockExpr(
   const MachineBasicBlock &SrcBB,
   const MachineOperand &MO) const {
   const MCExpr *DestBBSym
     = MCSymbolRefExpr::create(MO.getMBB()->getSymbol(), Ctx);
case MachineOperand::MO_MachineBasicBlock: {
 
     return true;
   }
   case MachineOperand::MO_GlobalAddress: {
     const GlobalValue *GV = MO.getGlobal();
     SmallString<128> SymbolName;
     AP.getNameWithPrefix(SymbolName, GV);
     MCSymbol *Sym = Ctx.getOrCreateSymbol(SymbolName);
-    const MCExpr *SymExpr =
+    const MCExpr *Expr =
       MCSymbolRefExpr::create(Sym, getVariantKind(MO.getTargetFlags()),Ctx);
-    const MCExpr *Expr = MCBinaryExpr::createAdd(SymExpr,
-      MCConstantExpr::create(MO.getOffset(), Ctx), Ctx);
+    int64_t Offset = MO.getOffset();
+    if (Offset != 0) {
+      Expr = MCBinaryExpr::createAdd(Expr,
+                                     MCConstantExpr::create(Offset, Ctx), Ctx);
+    }
     MCOp = MCOperand::createExpr(Expr);
     return true;
   }
   case MachineOperand::MO_ExternalSymbol: {
     MCSymbol *Sym = Ctx.getOrCreateSymbol(StringRef(MO.getSymbolName()));
     Sym->setExternal(true);
     const MCSymbolRefExpr *Expr = MCSymbolRefExpr::create(Sym, Ctx);
     MCOp = MCOperand::createExpr(Expr);

lib/Target/AMDGPU/MCTargetDesc/SIMCCodeEmitter.cpp

if (Reg != AMDGPU::VCC) {
     RegEnc &= SDWA9EncValues::VOPC_DST_SGPR_MASK;
     RegEnc |= SDWA9EncValues::VOPC_DST_VCC_MASK;
   }
   return RegEnc;
 }
 
 static bool needsPCRel(const MCExpr *Expr) {
   switch (Expr->getKind()) {
-  case MCExpr::SymbolRef:
+  case MCExpr::SymbolRef: {
+    auto *SE = cast<MCSymbolRefExpr>(Expr);
+    MCSymbolRefExpr::VariantKind Kind = SE->getKind();
+    if (Kind == MCSymbolRefExpr::VK_AMDGPU_ABS32_LO ||
+        Kind == MCSymbolRefExpr::VK_AMDGPU_ABS32_HI)
+      return false;
     return true;
+  }
   case MCExpr::Binary: {
     auto *BE = cast<MCBinaryExpr>(Expr);
     if (BE->getOpcode() == MCBinaryExpr::Sub)
       return false;
     return needsPCRel(BE->getLHS()) || needsPCRel(BE->getRHS());
   }
   case MCExpr::Unary:
     return needsPCRel(cast<MCUnaryExpr>(Expr)->getSubExpr());

lib/Target/AMDGPU/SIInstrInfo.h

enum TargetOperandFlags {
     MO_GOTPCREL32 = 2,
     MO_GOTPCREL32_LO = 2,
     // MO_GOTPCREL32_HI -> symbol@gotpcrel32@hi -> R_AMDGPU_GOTPCREL32_HI.
     MO_GOTPCREL32_HI = 3,
     // MO_REL32_LO -> symbol@rel32@lo -> R_AMDGPU_REL32_LO.
     MO_REL32 = 4,
     MO_REL32_LO = 4,
     // MO_REL32_HI -> symbol@rel32@hi -> R_AMDGPU_REL32_HI.
-    MO_REL32_HI = 5
+    MO_REL32_HI = 5,
+    MO_ABS32_LO = 6,
+    MO_ABS32_HI = 7,
   };
 
   explicit SIInstrInfo(const GCNSubtarget &ST);
 
   const SIRegisterInfo &getRegisterInfo() const {
     return RI;
   }
 

lib/Target/AMDGPU/SIInstrInfo.cpp

 
 ArrayRef<std::pair<unsigned, const char *>>
 SIInstrInfo::getSerializableDirectMachineOperandTargetFlags() const {
   static const std::pair<unsigned, const char *> TargetFlags[] = {
     { MO_GOTPCREL, "amdgpu-gotprel" },
     { MO_GOTPCREL32_LO, "amdgpu-gotprel32-lo" },
     { MO_GOTPCREL32_HI, "amdgpu-gotprel32-hi" },
     { MO_REL32_LO, "amdgpu-rel32-lo" },
-    { MO_REL32_HI, "amdgpu-rel32-hi" }
+    { MO_REL32_HI, "amdgpu-rel32-hi" },
+    { MO_ABS32_LO, "amdgpu-abs32-lo" },
+    { MO_ABS32_HI, "amdgpu-abs32-hi" },
   };
 
   return makeArrayRef(TargetFlags);
 }
 
 bool SIInstrInfo::isBasicBlockPrologue(const MachineInstr &MI) const {
   return !MI.isTerminator() && MI.getOpcode() != AMDGPU::COPY &&
          MI.modifiesRegister(AMDGPU::EXEC, &RI);