[WebAssembly] Fix CFI index for WebAssembly target to account for padding nullptr function

[ddcc]

The WebAssembly linker now creates a dummy function at index 0 to prevent miscomparisons with the NULL pointer, see https://github.com/WebAssembly/binaryen/pull/658. Thanks to pcc for pointing out this problem!

[dschuff]

LGTM, thanks for fixing that.

[dschuff]

Actually, I'm getting lit test failures with this patch (the changed parts of function.ll and function-ext.ll). Does that reproduce for you?

[ddcc]

Fix test failure

[dschuff]

(now LGTM, FTR)

lib/Transforms/IPO/LowerTypeTests.cpp

 /// Note: Dynamic linking is not supported, as the WebAssembly ABI has not yet
 /// been finalized.
 void LowerTypeTests::buildBitSetsFromFunctionsWASM(
     ArrayRef<Metadata *> TypeIds, ArrayRef<Function *> Functions) {
   assert(!Functions.empty());
 
   // Build consecutive monotonic integer ranges for each call target set
   DenseMap<GlobalObject *, uint64_t> GlobalLayout;
+
   for (Function *F : Functions) {
     // Skip functions that are not address taken, to avoid bloating the table
     if (!F->hasAddressTaken())
       continue;
 
     // Store metadata with the index for each function
     MDNode *MD = MDNode::get(F->getContext(),
                              ArrayRef<Metadata *>(ConstantAsMetadata::get(
static void init(LowerTypeTests *LTT, Module &M) {
   LTT->ObjectFormat = TargetTriple.getObjectFormat();
   LTT->Int1Ty = Type::getInt1Ty(M.getContext());
   LTT->Int8Ty = Type::getInt8Ty(M.getContext());
   LTT->Int32Ty = Type::getInt32Ty(M.getContext());
   LTT->Int32PtrTy = PointerType::getUnqual(LTT->Int32Ty);
   LTT->Int64Ty = Type::getInt64Ty(M.getContext());
   LTT->IntPtrTy = DL.getIntPtrType(M.getContext(), 0);
   LTT->TypeTestCallSites.clear();
-  LTT->IndirectIndex = 0;
+  LTT->IndirectIndex = 1;
 }
 
 bool LowerTypeTests::runOnModule(Module &M) {
   if (skipModule(M))
     return false;
   init(this, M);
   return lower();
 }

test/CodeGen/WebAssembly/cfi.ll

 ; RUN: opt -S -lowertypetests < %s | llc -asm-verbose=false -disable-wasm-fallthrough-return-opt | FileCheck %s
 
 ; Tests that we correctly assign indexes for control flow integrity.
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
 
 @0 = private unnamed_addr constant [2 x void (...)*] [void (...)* bitcast (void ()* @f to void (...)*), void (...)* bitcast (void ()* @g to void (...)*)], align 16
 
 ; CHECK-LABEL: h:
 ; CHECK-NOT: .indidx
 define void @h() !type !0 {
   ret void
 }
 
 ; CHECK-LABEL: f:
-; CHECK: .indidx 0
+; CHECK: .indidx 1
 define void @f() !type !0 {
   ret void
 }
 
 ; CHECK-LABEL: g:
-; CHECK: .indidx 1
+; CHECK: .indidx 2
 define void @g() !type !1 {
   ret void
 }
 
 !0 = !{i32 0, !"typeid1"}
 !1 = !{i32 0, !"typeid2"}
 
 declare i1 @llvm.type.test(i8* %ptr, metadata %bitset) nounwind readnone

test/Transforms/LowerTypeTests/function-disjoint.ll

 
 !0 = !{i32 0, !"typeid1"}
 !1 = !{i32 0, !"typeid2"}
 
 declare i1 @llvm.type.test(i8* %ptr, metadata %bitset) nounwind readnone
 
 define i1 @foo(i8* %p) {
   ; X64: icmp eq i64 {{.*}}, ptrtoint ([1 x <{ i8, i32, i8, i8, i8 }>]* @[[JT0]] to i64)
-  ; WASM32: icmp eq i64 {{.*}}, 0
+  ; WASM32: icmp eq i64 {{.*}}, 1
   %x = call i1 @llvm.type.test(i8* %p, metadata !"typeid1")
   ; X64: icmp eq i64 {{.*}}, ptrtoint ([1 x <{ i8, i32, i8, i8, i8 }>]* @[[JT1]] to i64)
-  ; WASM32: icmp eq i64 {{.*}}, 1
+  ; WASM32: icmp eq i64 {{.*}}, 2
   %y = call i1 @llvm.type.test(i8* %p, metadata !"typeid2")
   %z = add i1 %x, %y
   ret i1 %z
 }
 
-; WASM32: ![[I0]] = !{i64 0}
-; WASM32: ![[I1]] = !{i64 1}
+; WASM32: ![[I0]] = !{i64 1}
+; WASM32: ![[I1]] = !{i64 2}

test/Transforms/LowerTypeTests/function-ext.ll

define i1 @bar(i8* %ptr) {
   %p = call i1 @llvm.type.test(i8* %ptr, metadata !"void")
   ret i1 %p
 }
 
 declare i1 @llvm.type.test(i8* %ptr, metadata %bitset) nounwind readnone
 
 !0 = !{i64 0, !"void"}
 ; WASM-NOT: !{i64 0}
+; WASM-NOT: !{i64 1}

test/Transforms/LowerTypeTests/function.ll

 }
 
 !0 = !{i32 0, !"typeid1"}
 
 declare i1 @llvm.type.test(i8* %ptr, metadata %bitset) nounwind readnone
 
 define i1 @foo(i8* %p) {
   ; X64: sub i64 {{.*}}, ptrtoint ([2 x <{ i8, i32, i8, i8, i8 }>]* @[[JT]] to i64)
-  ; WASM32: sub i64 {{.*}}, 0
+  ; WASM32: sub i64 {{.*}}, 1
   ; WASM32: icmp ult i64 {{.*}}, 2
   %x = call i1 @llvm.type.test(i8* %p, metadata !"typeid1")
   ret i1 %x
 }
 
-; WASM32: ![[I0]] = !{i64 0}
-; WASM32: ![[I1]] = !{i64 1}
+; WASM32: ![[I0]] = !{i64 1}
+; WASM32: ![[I1]] = !{i64 2}