[WebAssembly] Implement -print-gc-sections, to better test GC of globals

Differential Revision: https://reviews.llvm.org/D44311

llvm-svn: 330456

6 files changed, 137 insertions, 14 deletions

diff --git a/lld/test/wasm/Inputs/globals.yaml b/lld/test/wasm/Inputs/globals.yaml
new file mode 100644
index 00000000000..98914f44527
--- /dev/null
+++ b/lld/test/wasm/Inputs/globals.yaml
@@ -0,0 +1,53 @@
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TYPE
+    Signatures:
+      - Index:           0
+        ReturnType:      I64
+        ParamTypes:
+  - Type:            FUNCTION
+    FunctionTypes:   [ 0 ]
+  - Type:            GLOBAL
+    Globals:
+      - Index:       0
+        Type:        I64
+        Mutable:     true
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           123
+      - Index:       1
+        Type:        I64
+        Mutable:     true
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           456
+  - Type:            CODE
+    Functions:
+      - Index:           0
+        Locals:
+        Body:            2381808080000B
+    Relocations:
+      - Type:            R_WEBASSEMBLY_GLOBAL_INDEX_LEB
+        Index:           1
+        Offset:          0x00000004
+  - Type:            CUSTOM
+    Name:            linking
+    SymbolTable:
+      - Index:           0
+        Kind:            GLOBAL
+        Name:            unused_global
+        Flags:           [ VISIBILITY_HIDDEN ]
+        Global:          0
+      - Index:           1
+        Kind:            GLOBAL
+        Name:            used_global
+        Flags:           [ VISIBILITY_HIDDEN ]
+        Global:          1
+      - Index:           2
+        Kind:            FUNCTION
+        Name:            use_global
+        Flags:           [ VISIBILITY_HIDDEN ]
+        Function:        0
+...
diff --git a/lld/test/wasm/gc-sections.ll b/lld/test/wasm/gc-sections.ll
index dec455e2811..d1e867e4b6b 100644
--- a/lld/test/wasm/gc-sections.ll
+++ b/lld/test/wasm/gc-sections.ll
@@ -1,16 +1,20 @@
 ; RUN: llc -filetype=obj %s -o %t.o
-; RUN: wasm-ld -print-gc-sections -o %t1.wasm %t.o | FileCheck %s -check-prefix=PRINT-GC
+; RUN: yaml2obj %S/Inputs/globals.yaml -o %t_globals.o
+; RUN: wasm-ld -print-gc-sections -o %t1.wasm %t.o %t_globals.o | \
+; RUN:     FileCheck %s -check-prefix=PRINT-GC
 ; PRINT-GC: removing unused section {{.*}}:(unused_function)
 ; PRINT-GC-NOT: removing unused section {{.*}}:(used_function)
 ; PRINT-GC: removing unused section {{.*}}:(.data.unused_data)
 ; PRINT-GC-NOT: removing unused section {{.*}}:(.data.used_data)
+; PRINT-GC: removing unused section {{.*}}:(unused_global)
+; PRINT-GC-NOT: removing unused section {{.*}}:(used_global)
 
 target triple = "wasm32-unknown-unknown-wasm"
 
 @unused_data = hidden global i64 1, align 4
 @used_data = hidden global i32 2, align 4
 
-define hidden i64 @unused_function() {
+define hidden i64 @unused_function(i64 %arg) {
   %1 = load i64, i64* @unused_data, align 4
   ret i64 %1
 }
@@ -20,24 +24,45 @@ define hidden i32 @used_function() {
   ret i32 %1
 }
 
+declare i64 @use_global()
+
 define hidden void @_start() {
 entry:
   call i32 @used_function()
+  call i64 @use_global()
   ret void
 }
 
 ; RUN: obj2yaml %t1.wasm | FileCheck %s
 
 ; CHECK:        - Type:            TYPE
-; CHECK-NEXT:     Signatures:      
+; CHECK-NEXT:     Signatures:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         ReturnType:      NORESULT
-; CHECK-NEXT:         ParamTypes:      
+; CHECK-NEXT:         ParamTypes:
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         ReturnType:      I32
-; CHECK-NEXT:         ParamTypes:      
+; CHECK-NEXT:         ParamTypes:
+; CHECK-NEXT:       - Index:           2
+; CHECK-NEXT:         ReturnType:      I64
+; CHECK-NEXT:         ParamTypes:
 ; CHECK-NEXT:   - Type:            FUNCTION
 
+; CHECK:        - Type:            GLOBAL
+; CHECK-NEXT:     Globals:
+; CHECK-NEXT:       - Index:           0
+; CHECK-NEXT:         Type:            I32
+; CHECK-NEXT:         Mutable:         true
+; CHECK-NEXT:         InitExpr:
+; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           66576
+; CHECK-NEXT:       - Index:       1
+; CHECK-NEXT:         Type:        I64
+; CHECK-NEXT:         Mutable:     true
+; CHECK-NEXT:         InitExpr:
+; CHECK-NEXT:           Opcode:          I64_CONST
+; CHECK-NEXT:           Value:           456
+
 ; CHECK:        - Type:            DATA
 ; CHECK-NEXT:     Segments:        
 ; CHECK-NEXT:       - SectionOffset:   7
@@ -55,24 +80,52 @@ entry:
 ; CHECK-NEXT:         Name:            used_function
 ; CHECK-NEXT:       - Index:           2
 ; CHECK-NEXT:         Name:            _start
+; CHECK-NEXT:       - Index:           3
+; CHECK-NEXT:         Name:            use_global
 ; CHECK-NEXT: ...
 
-; RUN: wasm-ld -print-gc-sections --no-gc-sections -o %t1.no-gc.wasm %t.o
+; RUN: wasm-ld -print-gc-sections --no-gc-sections -o %t1.no-gc.wasm \
+; RUN:     %t.o %t_globals.o
 ; RUN: obj2yaml %t1.no-gc.wasm | FileCheck %s -check-prefix=NO-GC
 
 ; NO-GC:        - Type:            TYPE
-; NO-GC-NEXT:     Signatures:      
+; NO-GC-NEXT:     Signatures:
 ; NO-GC-NEXT:       - Index:           0
 ; NO-GC-NEXT:         ReturnType:      NORESULT
 ; NO-GC-NEXT:         ParamTypes:
 ; NO-GC-NEXT:       - Index:           1
 ; NO-GC-NEXT:         ReturnType:      I64
-; NO-GC-NEXT:         ParamTypes:      
+; NO-GC-NEXT:         ParamTypes:
+; NO-GC-NEXT:           - I64
 ; NO-GC-NEXT:       - Index:           2
 ; NO-GC-NEXT:         ReturnType:      I32
-; NO-GC-NEXT:         ParamTypes:      
+; NO-GC-NEXT:         ParamTypes:
+; NO-GC-NEXT:       - Index:           3
+; NO-GC-NEXT:         ReturnType:      I64
+; NO-GC-NEXT:         ParamTypes:
 ; NO-GC-NEXT:   - Type:            FUNCTION
 
+; NO-GC:        - Type:            GLOBAL
+; NO-GC-NEXT:     Globals:
+; NO-GC-NEXT:       - Index:           0
+; NO-GC-NEXT:         Type:            I32
+; NO-GC-NEXT:         Mutable:         true
+; NO-GC-NEXT:         InitExpr:
+; NO-GC-NEXT:           Opcode:          I32_CONST
+; NO-GC-NEXT:           Value:           66576
+; NO-GC-NEXT:       - Index:       1
+; NO-GC-NEXT:         Type:        I64
+; NO-GC-NEXT:         Mutable:     true
+; NO-GC-NEXT:         InitExpr:
+; NO-GC-NEXT:           Opcode:          I64_CONST
+; NO-GC-NEXT:           Value:           123
+; NO-GC-NEXT:       - Index:       2
+; NO-GC-NEXT:         Type:        I64
+; NO-GC-NEXT:         Mutable:     true
+; NO-GC-NEXT:         InitExpr:
+; NO-GC-NEXT:           Opcode:          I64_CONST
+; NO-GC-NEXT:           Value:           456
+
 ; NO-GC:        - Type:            DATA
 ; NO-GC-NEXT:     Segments:        
 ; NO-GC-NEXT:       - SectionOffset:   7
@@ -92,6 +145,8 @@ entry:
 ; NO-GC-NEXT:         Name:            used_function
 ; NO-GC-NEXT:       - Index:           3
 ; NO-GC-NEXT:         Name:            _start
+; NO-GC-NEXT:       - Index:           4
+; NO-GC-NEXT:         Name:            use_global
 ; NO-GC-NEXT: ...
 
 ; RUN: not wasm-ld --gc-sections --relocatable -o %t1.no-gc.wasm %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-ERROR
diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
index 65c5ab24f61..f4fa6dc36c1 100644
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -340,7 +340,8 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
     Global.Type = {WASM_TYPE_I32, true};
     Global.InitExpr.Value.Int32 = 0;
     Global.InitExpr.Opcode = WASM_OPCODE_I32_CONST;
-    InputGlobal *StackPointer = make<InputGlobal>(Global);
+    Global.SymbolName = "__stack_pointer";
+    InputGlobal *StackPointer = make<InputGlobal>(Global, nullptr);
     StackPointer->Live = true;
 
     static WasmSignature NullSignature = {{}, WASM_TYPE_NORESULT};
diff --git a/lld/wasm/InputFiles.cpp b/lld/wasm/InputFiles.cpp
index 40a18ff6cf1..5b0afc07901 100644
--- a/lld/wasm/InputFiles.cpp
+++ b/lld/wasm/InputFiles.cpp
@@ -187,7 +187,7 @@ void ObjFile::parse() {
 
   // Populate `Globals`.
   for (const WasmGlobal &G : WasmObj->globals())
-    Globals.emplace_back(make<InputGlobal>(G));
+    Globals.emplace_back(make<InputGlobal>(G, this));
 
   // Populate `Symbols` based on the WasmSymbols in the object.
   Symbols.reserve(WasmObj->getNumberOfSymbols());
diff --git a/lld/wasm/InputGlobal.h b/lld/wasm/InputGlobal.h
index 16a6b7dd689..37d0ab90370 100644
--- a/lld/wasm/InputGlobal.h
+++ b/lld/wasm/InputGlobal.h
@@ -26,8 +26,10 @@ namespace wasm {
 // combined to form the final GLOBALS section.
 class InputGlobal {
 public:
-  InputGlobal(const WasmGlobal &G) : Global(G) {}
+  InputGlobal(const WasmGlobal &G, ObjFile *F)
+      : File(F), Global(G), Live(!Config->GcSections) {}
 
+  StringRef getName() const { return Global.SymbolName; }
   const WasmGlobalType &getType() const { return Global.Type; }
 
   uint32_t getGlobalIndex() const { return GlobalIndex.getValue(); }
@@ -37,16 +39,21 @@ public:
     GlobalIndex = Index;
   }
 
-  bool Live = false;
-
+  ObjFile *File;
   WasmGlobal Global;
 
+  bool Live = false;
+
 protected:
   llvm::Optional<uint32_t> GlobalIndex;
 };
 
 } // namespace wasm
 
+inline std::string toString(const wasm::InputGlobal *G) {
+  return (toString(G->File) + ":(" + G->getName() + ")").str();
+}
+
 } // namespace lld
 
 #endif // LLD_WASM_INPUT_GLOBAL_H
diff --git a/lld/wasm/MarkLive.cpp b/lld/wasm/MarkLive.cpp
index 2b30f6a2ffd..95d9782965e 100644
--- a/lld/wasm/MarkLive.cpp
+++ b/lld/wasm/MarkLive.cpp
@@ -22,6 +22,7 @@
 #include "MarkLive.h"
 #include "Config.h"
 #include "InputChunks.h"
+#include "InputGlobal.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
 
@@ -102,9 +103,15 @@ void lld::wasm::markLive() {
       for (InputChunk *C : Obj->Segments)
         if (!C->Live)
           message("removing unused section " + toString(C));
+      for (InputGlobal *G : Obj->Globals)
+        if (!G->Live)
+          message("removing unused section " + toString(G));
     }
     for (InputChunk *C : Symtab->SyntheticFunctions)
       if (!C->Live)
         message("removing unused section " + toString(C));
+    for (InputGlobal *G : Symtab->SyntheticGlobals)
+      if (!G->Live)
+        message("removing unused section " + toString(G));
   }
 }