commit 9d24fb7ff318d7a88f0fa3e63eb0df4acafd9805
author Sam Clegg <sbc@chromium.org> Fri Jun 16 23:59:10 2017 +0000
committer Sam Clegg <sbc@chromium.org> Fri Jun 16 23:59:10 2017 +0000
tree 831fda1fcb2d777624a62553479acb958f043e43
parent 4f1fca270acd736cbde43773d1fd83b3b3d2164f

[WebAssembly] Use __stack_pointer global when writing wasm binary

This ensures that symbolic relocations are generated for stack
pointer manipulations.

These relocations are of type R_WEBASSEMBLY_GLOBAL_INDEX_LEB.
This change also adds support for reading relocations of this
type in WasmObjectFile.cpp.

Since its a globally imported symbol this does mean that
the get_global/set_global instruction won't be valid until
the objects are linked that global used in no longer an
imported global.

Differential Revision: https://reviews.llvm.org/D34172

llvm-svn: 305616

llvm/lib/MC/WasmObjectWriter.cpp

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index db304c0..7ac4fb8 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -406,6 +406,8 @@
   }
 
   assert(!IsPCRel);
+  assert(SymA);
+
   unsigned Type = getRelocType(Target, Fixup);
 
   WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection);
@@ -474,6 +476,7 @@
     assert(IndirectSymbolIndices.count(RelEntry.Symbol));
     return IndirectSymbolIndices[RelEntry.Symbol];
   case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
+  case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
   case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB:
   case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB:
   case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32:
@@ -500,7 +503,8 @@
     switch (RelEntry.Type) {
     case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
     case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
-    case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB: {
+    case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
+    case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB: {
       uint32_t Index = getRelocationIndexValue(RelEntry);
       WritePatchableSLEB(Stream, Index, Offset);
       break;
@@ -526,7 +530,7 @@
       break;
     }
     default:
-      llvm_unreachable("unsupported relocation type");
+      llvm_unreachable("invalid relocation type");
     }
   }
 }