[WebAssembly] Default to static reloc model

lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

extern "C" void LLVMInitializeWebAssemblyTarget() {
   initializeWebAssemblyCallIndirectFixupPass(PR);
 }
 
 //===----------------------------------------------------------------------===//
 // WebAssembly Lowering public interface.
 //===----------------------------------------------------------------------===//
 
 static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
-  if (!RM.hasValue())
-    return Reloc::PIC_;
+  if (!RM.hasValue()) {
+    // Default to static relocation model.  This should always be more optimial
+    // than PIC since the static linker can determine all global addresses and
+    // assume direct function calls.
+    return Reloc::Static;
+  }
   return *RM;
 }
 
 /// Create an WebAssembly architecture model.
 ///
 WebAssemblyTargetMachine::WebAssemblyTargetMachine(
     const Target &T, const Triple &TT, StringRef CPU, StringRef FS,
     const TargetOptions &Options, Optional<Reloc::Model> RM,

test/CodeGen/WebAssembly/global.ll

 ; CHECK: .size    rom, 512{{$}}
 @rom = constant [128 x i32] zeroinitializer, align 16
 
 ; CHECK: .type       array,@object
 ; CHECK: array:
 ; CHECK-NEXT: .skip       8
 ; CHECK-NEXT: .size       array, 8
 ; CHECK: .type       pointer_to_array,@object
-; CHECK-NEXT: .section    .data.rel.ro.pointer_to_array,
+; CHECK-NEXT: .section    .rodata.pointer_to_array,
 ; CHECK-NEXT: .globl      pointer_to_array
 ; CHECK-NEXT: .p2align      2
 ; CHECK-NEXT: pointer_to_array:
 ; CHECK-NEXT: .int32      array+4
 ; CHECK-NEXT: .size       pointer_to_array, 4
 @array = internal constant [8 x i8] zeroinitializer, align 1
 @pointer_to_array = constant i8* getelementptr inbounds ([8 x i8], [8 x i8]* @array, i32 0, i32 4), align 4
 
 ; Handle external objects with opaque type.
 %struct.ASTRUCT = type opaque
 @g_struct = external global %struct.ASTRUCT, align 1
 define i32 @address_of_opaque()  {
   ret i32 ptrtoint (%struct.ASTRUCT* @g_struct to i32)
 }

test/CodeGen/WebAssembly/vtable.ll

 ; TYPEINFONAME-LABEL: _ZTS1C:
 ; TYPEINFONAME-NEXT: .asciz "1C"
 @_ZTS1C = constant [3 x i8] c"1C\00"
 ; TYPEINFONAME-LABEL: _ZTS1D:
 ; TYPEINFONAME-NEXT: .asciz "1D"
 @_ZTS1D = constant [3 x i8] c"1D\00"
 
 ; VTABLE:       .type _ZTV1A,@object
-; VTABLE-NEXT:  .section .data.rel.ro._ZTV1A,
+; VTABLE-NEXT:  .section .rodata._ZTV1A,
 ; VTABLE-NEXT:  .globl _ZTV1A
 ; VTABLE-LABEL: _ZTV1A:
 ; VTABLE-NEXT:  .int32 0
 ; VTABLE-NEXT:  .int32 _ZTI1A
 ; VTABLE-NEXT:  .int32 _ZN1AD2Ev
 ; VTABLE-NEXT:  .int32 _ZN1AD0Ev
 ; VTABLE-NEXT:  .int32 _ZN1A3fooEv
 ; VTABLE-NEXT:  .size _ZTV1A, 20
 @_ZTV1A = constant [5 x i8*] [i8* null, i8* bitcast ({ i8*, i8* }* @_ZTI1A to i8*), i8* bitcast (%struct.A* (%struct.A*)* @_ZN1AD2Ev to i8*), i8* bitcast (void (%struct.A*)* @_ZN1AD0Ev to i8*), i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*)], align 4
 ; VTABLE:       .type _ZTV1B,@object
-; VTABLE-NEXT:  .section .data.rel.ro._ZTV1B,
+; VTABLE-NEXT:  .section .rodata._ZTV1B,
 ; VTABLE-NEXT:  .globl _ZTV1B
 ; VTABLE-LABEL: _ZTV1B:
 ; VTABLE-NEXT:  .int32 0
 ; VTABLE-NEXT:  .int32 _ZTI1B
 ; VTABLE-NEXT:  .int32 _ZN1AD2Ev
 ; VTABLE-NEXT:  .int32 _ZN1BD0Ev
 ; VTABLE-NEXT:  .int32 _ZN1B3fooEv
 ; VTABLE-NEXT:  .size _ZTV1B, 20
 @_ZTV1B = constant [5 x i8*] [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI1B to i8*), i8* bitcast (%struct.A* (%struct.A*)* @_ZN1AD2Ev to i8*), i8* bitcast (void (%struct.B*)* @_ZN1BD0Ev to i8*), i8* bitcast (void (%struct.B*)* @_ZN1B3fooEv to i8*)], align 4
 ; VTABLE:       .type _ZTV1C,@object
-; VTABLE-NEXT:  .section .data.rel.ro._ZTV1C,
+; VTABLE-NEXT:  .section .rodata._ZTV1C,
 ; VTABLE-NEXT:  .globl _ZTV1C
 ; VTABLE-LABEL: _ZTV1C:
 ; VTABLE-NEXT:  .int32 0
 ; VTABLE-NEXT:  .int32 _ZTI1C
 ; VTABLE-NEXT:  .int32 _ZN1AD2Ev
 ; VTABLE-NEXT:  .int32 _ZN1CD0Ev
 ; VTABLE-NEXT:  .int32 _ZN1C3fooEv
 ; VTABLE-NEXT:  .size _ZTV1C, 20
 @_ZTV1C = constant [5 x i8*] [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI1C to i8*), i8* bitcast (%struct.A* (%struct.A*)* @_ZN1AD2Ev to i8*), i8* bitcast (void (%struct.C*)* @_ZN1CD0Ev to i8*), i8* bitcast (void (%struct.C*)* @_ZN1C3fooEv to i8*)], align 4
 ; VTABLE:       .type _ZTV1D,@object
-; VTABLE-NEXT:  .section .data.rel.ro._ZTV1D,
+; VTABLE-NEXT:  .section .rodata._ZTV1D,
 ; VTABLE-NEXT:  .globl _ZTV1D
 ; VTABLE-LABEL: _ZTV1D:
 ; VTABLE-NEXT:  .int32 0
 ; VTABLE-NEXT:  .int32 _ZTI1D
 ; VTABLE-NEXT:  .int32 _ZN1AD2Ev
 ; VTABLE-NEXT:  .int32 _ZN1DD0Ev
 ; VTABLE-NEXT:  .int32 _ZN1D3fooEv
 ; VTABLE-NEXT:  .size _ZTV1D, 20