[WebAssembly] Fix stack pointer relocations

[sbc100]

Summary

This line was mistakenly deleted in rL319813

Add a test for stackpointer relocations.

[ruiu]

LGTM

test/wasm/stack-pointer.ll

+; RUN: llc -filetype=obj %s -o %t.o
+; RUN: lld -flavor wasm --emit-relocs -o %t.wasm %t.o
+; RUN: obj2yaml %t.wasm | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown-wasm"
+
+; Function Attrs: nounwind
+define hidden i32 @_start() local_unnamed_addr {
+entry:
+  %retval = alloca i32, align 4
+  ret i32 0
+}
+
+; CHECK:      --- !WASM
+; CHECK-NEXT: FileHeader:      
+; CHECK-NEXT:   Version:         0x00000001
+; CHECK-NEXT: Sections:        
+; CHECK-NEXT:   - Type:            TYPE
+; CHECK-NEXT:     Signatures:      
+; CHECK-NEXT:       - Index:           0
+; CHECK-NEXT:         ReturnType:      I32
+; CHECK-NEXT:         ParamTypes:      
+; CHECK-NEXT:   - Type:            FUNCTION
+; CHECK-NEXT:     FunctionTypes:   [ 0 ]
+; CHECK-NEXT:   - Type:            TABLE
+; CHECK-NEXT:     Tables:          
+; CHECK-NEXT:       - ElemType:        ANYFUNC
+; CHECK-NEXT:         Limits:          
+; CHECK-NEXT:           Flags:           0x00000001
+; CHECK-NEXT:           Initial:         0x00000001
+; CHECK-NEXT:           Maximum:         0x00000001
+; CHECK-NEXT:   - Type:            MEMORY
+; CHECK-NEXT:     Memories:        
+; CHECK-NEXT:       - Initial:         0x00000002
+; CHECK-NEXT:   - Type:            GLOBAL
+; CHECK-NEXT:     Globals:         
+; CHECK-NEXT:       - Type:            I32
+; CHECK-NEXT:         Mutable:         true
+; CHECK-NEXT:         InitExpr:        
+; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           66560
+; CHECK-NEXT:   - Type:            EXPORT
+; CHECK-NEXT:     Exports:         
+; CHECK-NEXT:       - Name:            memory
+; CHECK-NEXT:         Kind:            MEMORY
+; CHECK-NEXT:         Index:           0
+; CHECK-NEXT:       - Name:            _start
+; CHECK-NEXT:         Kind:            FUNCTION
+; CHECK-NEXT:         Index:           0
+; CHECK-NEXT:   - Type:            CODE
+; CHECK-NEXT:     Relocations:     
+; CHECK-NEXT:       - Type:            R_WEBASSEMBLY_GLOBAL_INDEX_LEB
+; CHECK-NEXT:         Index:           0
+; CHECK-NEXT:         Offset:          0x00000004
+; CHECK-NEXT:     Functions:       
+; CHECK-NEXT:       - Locals:          
+; CHECK-NEXT:         Body:            23808080800041106B1A41000B
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            linking
+; CHECK-NEXT:     DataSize:        0
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            name
+; CHECK-NEXT:     FunctionNames:   
+; CHECK-NEXT:       - Index:           0
+; CHECK-NEXT:         Name:            _start
+; CHECK-NEXT: ...

wasm/Driver.cpp

 // Inject a new wasm global into the output binary with the given value.
 // Wasm global are used in relocatable object files to model symbol imports
 // and exports.  In the final executable the only use of wasm globals is
 // for the exlicit stack pointer (__stack_pointer).
 static Symbol* addSyntheticGlobal(StringRef Name, int32_t Value) {
   log("injecting global: " + Name);
   Symbol *S = Symtab->addDefinedGlobal(Name);
   S->setVirtualAddress(Value);
+  S->setOutputIndex(Config->SyntheticGlobals.size());
   Config->SyntheticGlobals.emplace_back(S);
   return S;
 }
 
 // Inject a new undefined symbol into the link.  This will cause the link to
 // fail unless this symbol can be found.
 static void addSyntheticUndefinedFunction(StringRef Name,
                                           const WasmSignature *Type) {