[lld] fad0546 - [lld][WebAssembly] Handle TLS variables in Symbol::getVA. NFC

[Sam Clegg via llvm-commits]

Author: Sam Clegg
Date: 2021-10-29T10:45:30-07:00
New Revision: fad05465c16f123567d40e7e5cbeea69aa6e5c91

URL: https://github.com/llvm/llvm-project/commit/fad05465c16f123567d40e7e5cbeea69aa6e5c91
DIFF: https://github.com/llvm/llvm-project/commit/fad05465c16f123567d40e7e5cbeea69aa6e5c91.diff

LOG: [lld][WebAssembly] Handle TLS variables in Symbol::getVA. NFC

In the shared memory case we can always assume that TLS addresses
are relative to __tls_base.  In the non-shared memory case TLS
variables are absolute, just like normal data addresses.

This simplifies the code in calcNewValue so that TLS relocations
no longer need special handling.

Differential Revision: https://reviews.llvm.org/D112831

Added: 
    

Modified: 
    lld/wasm/InputFiles.cpp
    lld/wasm/Symbols.cpp

Removed: 
    


################################################################################
diff  --git a/lld/wasm/InputFiles.cpp b/lld/wasm/InputFiles.cpp
index bf47f8bb24674..3fe8846984bf3 100644
--- a/lld/wasm/InputFiles.cpp
+++ b/lld/wasm/InputFiles.cpp
@@ -169,18 +169,12 @@ uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone,
   case R_WASM_MEMORY_ADDR_REL_SLEB64:
   case R_WASM_MEMORY_ADDR_I32:
   case R_WASM_MEMORY_ADDR_I64:
+  case R_WASM_MEMORY_ADDR_TLS_SLEB:
+  case R_WASM_MEMORY_ADDR_TLS_SLEB64:
   case R_WASM_MEMORY_ADDR_LOCREL_I32: {
     if (isa<UndefinedData>(sym) || sym->isUndefWeak())
       return 0;
     auto D = cast<DefinedData>(sym);
-    // Treat non-TLS relocation against symbols that live in the TLS segment
-    // like TLS relocations.  This behaviour exists to support older object
-    // files created before we introduced TLS relocations.
-    // TODO(sbc): Remove this legacy behaviour one day.  This will break
-    // backward compat with old object files built with `-fPIC`.
-    if (D->segment && D->segment->outputSeg->isTLS())
-      return D->getOutputSegmentOffset() + reloc.Addend;
-
     uint64_t value = D->getVA() + reloc.Addend;
     if (reloc.Type == R_WASM_MEMORY_ADDR_LOCREL_I32) {
       const auto *segment = cast<InputSegment>(chunk);
@@ -190,12 +184,6 @@ uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone,
     }
     return value;
   }
-  case R_WASM_MEMORY_ADDR_TLS_SLEB:
-  case R_WASM_MEMORY_ADDR_TLS_SLEB64:
-    if (isa<UndefinedData>(sym) || sym->isUndefWeak())
-      return 0;
-    // TLS relocations are relative to the start of the TLS output segment
-    return cast<DefinedData>(sym)->getOutputSegmentOffset() + reloc.Addend;
   case R_WASM_TYPE_INDEX_LEB:
     return typeMap[reloc.Index];
   case R_WASM_FUNCTION_INDEX_LEB:

diff  --git a/lld/wasm/Symbols.cpp b/lld/wasm/Symbols.cpp
index 39c91a11e20e7..684f4832b2678 100644
--- a/lld/wasm/Symbols.cpp
+++ b/lld/wasm/Symbols.cpp
@@ -305,6 +305,11 @@ uint32_t DefinedFunction::getExportedFunctionIndex() const {
 
 uint64_t DefinedData::getVA() const {
   LLVM_DEBUG(dbgs() << "getVA: " << getName() << "\n");
+  // In the shared memory case, TLS symbols are relative to the start of the TLS
+  // output segment (__tls_base).  When building without shared memory, TLS
+  // symbols absolute, just like non-TLS.
+  if (isTLS() && config->sharedMemory)
+    return getOutputSegmentOffset() + value;
   if (segment)
     return segment->getVA(value);
   return value;