Add emitWcsLen helper function

[anjankgk]

Summary

Add implementations for generic function of emitWcsLen on the similar lines to the existing helper functions of different types.

[lebedev.ri]

llvm/include/llvm/IR/IRBuilder.h

565 ↗

(On Diff #337493)

These two don't carry their weight.
In LLVM IR, pointer types are going away soon.

[anjankgk]

llvm/include/llvm/IR/IRBuilder.h

565 ↗

(On Diff #337493)

Is there another substitute type for the PointerType if this is going to be removed?

[lebedev.ri]

llvm/include/llvm/IR/IRBuilder.h

565 ↗

(On Diff #337493)

I meant, the pointers will loose their pointee type.
I suggest to simply inline this into the only callee.

[Whitney]

llvm/include/llvm/Transforms/Utils/BuildLibCalls.h

53

Ptr is required to be wchar pointer type

can we assert that?

[anjankgk]

Add an assert to check the pointer param

[xbolva00]

Where do you plan to use this new helper?

[anjankgk]

In D100496#2698553, @xbolva00 wrote:

Where do you plan to use this new helper?

I have a patch (D88460) that replaces strlen idiom (for i8s), but shortly after I want to add another patch for generic type (i16/i32/wchar), this will be reqd there.

[anjankgk]

gentle ping for a review request..
Thanks!

[xbolva00]

Please commit this one when second patch is accepted

[lebedev.ri]

This review seems to be stuck/dead, consider abandoning if no longer relevant.

llvm/include/llvm/Transforms/Utils/BuildLibCalls.h

namespace llvm {
   Value *castToCStr(Value *V, IRBuilderBase &B);
 
   /// Emit a call to the strlen function to the builder, for the specified
   /// pointer. Ptr is required to be some pointer type, and the return value has
   /// 'intptr_t' type.
   Value *emitStrLen(Value *Ptr, IRBuilderBase &B, const DataLayout &DL,
                     const TargetLibraryInfo *TLI);
 
+  /// Emit a call to the wcslen function to the builder, for the specified
+  /// pointer. Ptr is required to be wchar pointer type, and the return value
+  /// has 'intptr_t' type.
+  Value *emitWcsLen(Value *Ptr, IRBuilderBase &B, const DataLayout &DL,
+                    const TargetLibraryInfo *TLI);
+
   /// Emit a call to the strdup function to the builder, for the specified
   /// pointer. Ptr is required to be some pointer type, and the return value has
   /// 'i8*' type.
   Value *emitStrDup(Value *Ptr, IRBuilderBase &B, const TargetLibraryInfo *TLI);
 
   /// Emit a call to the strnlen function to the builder, for the specified
   /// pointer. Ptr is required to be some pointer type, MaxLen must be of size_t
   /// type, and the return value has 'intptr_t' type.

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

 
 Value *llvm::emitStrLen(Value *Ptr, IRBuilderBase &B, const DataLayout &DL,
                         const TargetLibraryInfo *TLI) {
   LLVMContext &Context = B.GetInsertBlock()->getContext();
   return emitLibCall(LibFunc_strlen, DL.getIntPtrType(Context),
                      B.getInt8PtrTy(), castToCStr(Ptr, B), B, TLI);
 }
 
+Value *llvm::emitWcsLen(Value *Ptr, IRBuilderBase &B, const DataLayout &DL,
+                        const TargetLibraryInfo *TLI) {
+  LLVMContext &Context = B.GetInsertBlock()->getContext();
+
+  // know the wchar size before emiting the call to wcslen
+  Module &M = *B.GetInsertBlock()->getModule();
+  unsigned WCharSize = TLI->getWCharSize(M);
+
+  assert(Ptr->getType()->getPointerElementType()->isIntegerTy(WCharSize * 8) &&
+         "Pointer parameter must be of WChar type");
+
+  Type *PtrTy = nullptr;
+  switch (WCharSize) {
+  default:
+    // We cannot perform this optimization without wchar_size metadata.
+    return nullptr;
+  case 2:
+    PtrTy = Type::getInt16PtrTy(Context);
+    break;
+  case 4:
+    PtrTy = Type::getInt32PtrTy(Context);
+    break;
+  }
+
+  // emit the appropriate wcslen call
+  return emitLibCall(LibFunc_wcslen, DL.getIntPtrType(Context), PtrTy, Ptr, B,
+                     TLI);
+}
+
 Value *llvm::emitStrDup(Value *Ptr, IRBuilderBase &B,
                         const TargetLibraryInfo *TLI) {
   return emitLibCall(LibFunc_strdup, B.getInt8PtrTy(), B.getInt8PtrTy(),
                      castToCStr(Ptr, B), B, TLI);
 }
 
 Value *llvm::emitStrChr(Value *Ptr, char C, IRBuilderBase &B,
                         const TargetLibraryInfo *TLI) {