[WebAssembly] Support creation and import of shared memories

dschuff · dschuff · commit 3bea8bcae5f3 · 2018-11-06T17:59:32.000Z
Used for WebAssembly threads proposal. Add a flag --shared-memory which sets the IS_SHARED bit in WasmLimits Differential Revision: https://reviews.llvm.org/D54130 llvm-svn: 346248
diff --git a/lld/test/wasm/data-layout.ll b/lld/test/wasm/data-layout.ll
@@ -68,6 +68,16 @@ target triple = "wasm32-unknown-unknown"
 ; CHECK-MAX-NEXT:         Initial:         0x00000002
 ; CHECK-MAX-NEXT:         Maximum:         0x00000002
 
+; RUN: wasm-ld -no-gc-sections --allow-undefined --no-entry --shared-memory \
+; RUN:     --initial-memory=131072 --max-memory=131072 -o %t_max.wasm %t.o \
+; RUN:     %t.hello.o
+; RUN: obj2yaml %t_max.wasm | FileCheck %s -check-prefix=CHECK-SHARED
+
+; CHECK-SHARED:        - Type:            MEMORY
+; CHECK-SHARED-NEXT:     Memories:
+; CHECK-SHARED-NEXT:       - Flags:           [ HAS_MAX, IS_SHARED ]
+; CHECK-SHARED-NEXT:         Initial:         0x00000002
+; CHECK-SHARED-NEXT:         Maximum:         0x00000002
 
 ; RUN: wasm-ld --relocatable -o %t_reloc.wasm %t.o %t.hello.o
 ; RUN: obj2yaml %t_reloc.wasm | FileCheck %s -check-prefix=RELOC
diff --git a/lld/test/wasm/import-memory.test b/lld/test/wasm/import-memory.test
@@ -31,3 +31,20 @@
 # CHECK-MAX-NEXT:          Initial:         0x00000004
 # CHECK-MAX-NEXT:          Maximum:         0x00000005
 # CHECK-MAX-NEXT:  - Type:
+
+# RUN: wasm-ld --import-memory --shared-memory --initial-memory=262144 \
+# RUN:     --max-memory=327680 -o %t.max.wasm %t.start.o
+# RUN: obj2yaml %t.max.wasm | FileCheck -check-prefix=CHECK-SHARED %s
+
+# Verify the --shared-memory flag works with imports
+
+# CHECK-SHARED:       - Type:            IMPORT
+# CHECK-SHARED-NEXT:    Imports:
+# CHECK-SHARED-NEXT:      - Module:          env
+# CHECK-SHARED-NEXT:        Field:           memory
+# CHECK-SHARED-NEXT:        Kind:            MEMORY
+# CHECK-SHARED-NEXT:        Memory:
+# CHECK-SHARED-NEXT:          Flags:           [ HAS_MAX, IS_SHARED ]
+# CHECK-SHARED-NEXT:          Initial:         0x00000004
+# CHECK-SHARED-NEXT:          Maximum:         0x00000005
+# CHECK-SHARED-NEXT:  - Type:
diff --git a/lld/wasm/Config.h b/lld/wasm/Config.h
@@ -28,6 +28,7 @@ struct Configuration {
   bool ExportTable;
   bool GcSections;
   bool ImportMemory;
+  bool SharedMemory;
   bool ImportTable;
   bool MergeDataSegments;
   bool PrintGcSections;
diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
@@ -381,6 +381,7 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   errorHandler().FatalWarnings =
       Args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
   Config->ImportMemory = Args.hasArg(OPT_import_memory);
+  Config->SharedMemory = Args.hasArg(OPT_shared_memory);
   Config->ImportTable = Args.hasArg(OPT_import_table);
   Config->LTOO = args::getInteger(Args, OPT_lto_O, 2);
   Config->LTOPartitions = args::getInteger(Args, OPT_lto_partitions, 1);
diff --git a/lld/wasm/Options.td b/lld/wasm/Options.td
@@ -123,6 +123,9 @@ def global_base: J<"global-base=">,
 def import_memory: F<"import-memory">,
   HelpText<"Import memory from the environment">;
 
+def shared_memory: F<"shared-memory">,
+  HelpText<"Use shared linear memory">;
+
 def import_table: F<"import-table">,
   HelpText<"Import function table from the environment">;
 
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
@@ -155,6 +155,9 @@ void Writer::createImportSection() {
       Import.Memory.Flags |= WASM_LIMITS_FLAG_HAS_MAX;
       Import.Memory.Maximum = MaxMemoryPages;
     }
+    if (Config->SharedMemory) {
+      Import.Memory.Flags |= WASM_LIMITS_FLAG_IS_SHARED;
+    }
     writeImport(OS, Import);
   }
 
@@ -214,8 +217,10 @@ void Writer::createMemorySection() {
 
   bool HasMax = MaxMemoryPages != 0;
   writeUleb128(OS, 1, "memory count");
-  writeUleb128(OS, HasMax ? static_cast<unsigned>(WASM_LIMITS_FLAG_HAS_MAX) : 0,
-               "memory limits flags");
+  unsigned Flags = HasMax ? static_cast<unsigned>(WASM_LIMITS_FLAG_HAS_MAX) : 0;
+  if (Config->SharedMemory)
+    Flags |= WASM_LIMITS_FLAG_IS_SHARED;
+  writeUleb128(OS, Flags, "memory limits flags");
   writeUleb128(OS, NumMemoryPages, "initial pages");
   if (HasMax)
     writeUleb128(OS, MaxMemoryPages, "max pages");
