[WebAssembly] Add new explicit relocation types for PIC relocations

See https://github.com/WebAssembly/tool-conventions/pull/106

Differential Revision: https://reviews.llvm.org/D59907

llvm-svn: 357710

4 files changed, 63 insertions, 26 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index 69c477bbbb5..4c7114eea11 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -90,9 +90,21 @@ namespace WebAssemblyII {
 enum TOF {
   MO_NO_FLAG = 0,
 
-  // Address of data symbol via a wasm global.  This adds a level of indirection
-  // similar to the GOT on native platforms.
+  // On a symbol operand this indicates that the immediate is a wasm global
+  // index.  The value of the wasm global will be set to the symbol address at
+  // runtime.  This adds a level of indirection similar to the GOT on native
+  // platforms.
   MO_GOT,
+
+  // On a symbol operand this indicates that the immediate is the symbol
+  // address relative the __memory_base wasm global.
+  // Only applicable to data symbols.
+  MO_MEMORY_BASE_REL,
+
+  // On a symbol operand this indicates that the immediate is the symbol
+  // address relative the __table_base wasm global.
+  // Only applicable to function symbols.
+  MO_TABLE_BASE_REL,
 };
 
 } // end namespace WebAssemblyII
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
index 91b356db81d..a1cc3e268e8 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
@@ -42,14 +42,6 @@ private:
 WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit)
     : MCWasmObjectTargetWriter(Is64Bit) {}
 
-static bool isFunctionSignatureRef(const MCSymbolRefExpr *Ref) {
-  return Ref->getKind() == MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX;
-}
-
-static bool isGOTRef(const MCSymbolRefExpr *Ref) {
-  return Ref->getKind() == MCSymbolRefExpr::VK_GOT;
-}
-
 static const MCSection *getFixupSection(const MCExpr *Expr) {
   if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr)) {
     if (SyExp->getSymbol().isInSection())
@@ -75,6 +67,23 @@ unsigned WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
   assert(RefA);
   auto& SymA = cast<MCSymbolWasm>(RefA->getSymbol());
 
+  MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
+
+  switch (Modifier) {
+    case MCSymbolRefExpr::VK_GOT:
+      return wasm::R_WASM_GLOBAL_INDEX_LEB;
+    case MCSymbolRefExpr::VK_WASM_TBREL:
+      assert(SymA.isFunction());
+      return wasm::R_WASM_TABLE_INDEX_REL_SLEB;
+    case MCSymbolRefExpr::VK_WASM_MBREL:
+      assert(SymA.isData());
+      return wasm::R_WASM_MEMORY_ADDR_REL_SLEB;
+    case MCSymbolRefExpr::VK_WASM_TYPEINDEX:
+      return wasm::R_WASM_TYPE_INDEX_LEB;
+    default:
+      break;
+  }
+
   switch (unsigned(Fixup.getKind())) {
   case WebAssembly::fixup_sleb128_i32:
     if (SymA.isFunction())
@@ -83,14 +92,10 @@ unsigned WebAssemblyWasmObjectWriter::getRelocType(const MCValue &Target,
   case WebAssembly::fixup_sleb128_i64:
     llvm_unreachable("fixup_sleb128_i64 not implemented yet");
   case WebAssembly::fixup_uleb128_i32:
-    if (SymA.isGlobal() || isGOTRef(RefA))
+    if (SymA.isGlobal())
       return wasm::R_WASM_GLOBAL_INDEX_LEB;
-    if (SymA.isFunction()) {
-      if (isFunctionSignatureRef(RefA))
-        return wasm::R_WASM_TYPE_INDEX_LEB;
-      else
-        return wasm::R_WASM_FUNCTION_INDEX_LEB;
-    }
+    if (SymA.isFunction())
+      return wasm::R_WASM_FUNCTION_INDEX_LEB;
     if (SymA.isEvent())
       return wasm::R_WASM_EVENT_INDEX_LEB;
     return wasm::R_WASM_MEMORY_ADDR_LEB;
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index b5e9d9e9723..7bad4972c4f 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -1003,17 +1003,22 @@ SDValue WebAssemblyTargetLowering::LowerGlobalAddress(SDValue Op,
       MachineFunction &MF = DAG.getMachineFunction();
       MVT PtrVT = getPointerTy(MF.getDataLayout());
       const char *BaseName;
-      if (GV->getValueType()->isFunctionTy())
+      if (GV->getValueType()->isFunctionTy()) {
         BaseName = MF.createExternalSymbolName("__table_base");
-      else
+        OperandFlags = WebAssemblyII::MO_TABLE_BASE_REL;
+      }
+      else {
         BaseName = MF.createExternalSymbolName("__memory_base");
+        OperandFlags = WebAssemblyII::MO_MEMORY_BASE_REL;
+      }
       SDValue BaseAddr =
           DAG.getNode(WebAssemblyISD::Wrapper, DL, PtrVT,
                       DAG.getTargetExternalSymbol(BaseName, PtrVT));
 
       SDValue SymAddr = DAG.getNode(
           WebAssemblyISD::WrapperPIC, DL, VT,
-          DAG.getTargetGlobalAddress(GA->getGlobal(), DL, VT, GA->getOffset()));
+          DAG.getTargetGlobalAddress(GA->getGlobal(), DL, VT, GA->getOffset(),
+                                     OperandFlags));
 
       return DAG.getNode(ISD::ADD, DL, VT, BaseAddr, SymAddr);
     } else {
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
index fd09b749c73..27f13d9639a 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
@@ -122,16 +122,31 @@ MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
 
 MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
                                                      MCSymbol *Sym) const {
-  bool isGOT = MO.getTargetFlags() == WebAssemblyII::MO_GOT;
-  MCSymbolRefExpr::VariantKind Kind =
-      isGOT ? MCSymbolRefExpr::VK_GOT : MCSymbolRefExpr::VK_None;
+  MCSymbolRefExpr::VariantKind Kind = MCSymbolRefExpr::VK_None;
+  unsigned TargetFlags = MO.getTargetFlags();
+
+  switch (TargetFlags) {
+    case WebAssemblyII::MO_NO_FLAG:
+      break;
+    case WebAssemblyII::MO_GOT:
+      Kind = MCSymbolRefExpr::VK_GOT;
+      break;
+    case WebAssemblyII::MO_MEMORY_BASE_REL:
+      Kind = MCSymbolRefExpr::VK_WASM_MBREL;
+      break;
+    case WebAssemblyII::MO_TABLE_BASE_REL:
+      Kind = MCSymbolRefExpr::VK_WASM_TBREL;
+      break;
+    default:
+      llvm_unreachable("Unknown target flag on GV operand");
+  }
+
   const MCExpr *Expr = MCSymbolRefExpr::create(Sym, Kind, Ctx);
 
   if (MO.getOffset() != 0) {
     const auto *WasmSym = cast<MCSymbolWasm>(Sym);
-    if (isGOT)
+    if (TargetFlags == WebAssemblyII::MO_GOT)
       report_fatal_error("GOT symbol references do not support offsets");
-
     if (WasmSym->isFunction())
       report_fatal_error("Function addresses with offsets not supported");
     if (WasmSym->isGlobal())
@@ -217,7 +232,7 @@ void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
           WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 
           const MCExpr *Expr = MCSymbolRefExpr::create(
-              WasmSym, MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX, Ctx);
+              WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
           MCOp = MCOperand::createExpr(Expr);
           break;
         }