Emit inline implementation of __builtin__wmemchr on MSVCRT platforms.

[akhuang]

Summary

The MSVC runtime library doesn't have a definition for wmemchr,
so provide an inline implementation.

[rnk]

lgtm w nit

clang/test/CodeGen/wmemchr.c

8

I'd start these off with CHECK-LABEL: define i16* @wmemchr_test as a little bit of future proofing.

[akhuang]

add CHECK line to test

clang/lib/CodeGen/CGBuiltin.cpp

if (Size.ugt(DstSize))
       break;
     Address Dest = EmitPointerWithAlignment(E->getArg(0));
     Value *ByteVal = Builder.CreateTrunc(EmitScalarExpr(E->getArg(1)),
                                          Builder.getInt8Ty());
     Value *SizeVal = llvm::ConstantInt::get(Builder.getContext(), Size);
     Builder.CreateMemSet(Dest, ByteVal, SizeVal, false);
     return RValue::get(Dest.getPointer());
   }
+  case Builtin::BI__builtin_wmemchr: {
+    // The MSVC runtime library does not provide a definition of wmemchr, so we
+    // need an inline implementation.
+    if (!getTarget().getTriple().isOSMSVCRT())
+      break;
+
+    llvm::Type *WCharTy = ConvertType(getContext().WCharTy);
+    Value *Str = EmitScalarExpr(E->getArg(0));
+    Value *Chr = EmitScalarExpr(E->getArg(1));
+    Value *Size = EmitScalarExpr(E->getArg(2));
+
+    BasicBlock *Entry = Builder.GetInsertBlock();
+    BasicBlock *CmpEq = createBasicBlock("wmemchr.eq");
+    BasicBlock *Next = createBasicBlock("wmemchr.next");
+    BasicBlock *Exit = createBasicBlock("wmemchr.exit");
+    Value *SizeEq0 = Builder.CreateICmpEQ(Size, ConstantInt::get(SizeTy, 0));
+    Builder.CreateCondBr(SizeEq0, Exit, CmpEq);
+
+    EmitBlock(CmpEq);
+    PHINode *StrPhi = Builder.CreatePHI(Str->getType(), 2);
+    StrPhi->addIncoming(Str, Entry);
+    PHINode *SizePhi = Builder.CreatePHI(SizeTy, 2);
+    SizePhi->addIncoming(Size, Entry);
+    CharUnits WCharAlign =
+        getContext().getTypeAlignInChars(getContext().WCharTy);
+    Value *StrCh = Builder.CreateAlignedLoad(WCharTy, StrPhi, WCharAlign);
+    Value *FoundChr = Builder.CreateConstInBoundsGEP1_32(WCharTy, StrPhi, 0);
+    Value *StrEqChr = Builder.CreateICmpEQ(StrCh, Chr);
+    Builder.CreateCondBr(StrEqChr, Exit, Next);
+
+    EmitBlock(Next);
+    Value *NextStr = Builder.CreateConstInBoundsGEP1_32(WCharTy, StrPhi, 1);
+    Value *NextSize = Builder.CreateSub(SizePhi, ConstantInt::get(SizeTy, 1));
+    Value *NextSizeEq0 =
+        Builder.CreateICmpEQ(NextSize, ConstantInt::get(SizeTy, 0));
+    Builder.CreateCondBr(NextSizeEq0, Exit, CmpEq);
+    StrPhi->addIncoming(NextStr, Next);
+    SizePhi->addIncoming(NextSize, Next);
+
+    EmitBlock(Exit);
+    PHINode *Ret = Builder.CreatePHI(Str->getType(), 3);
+    Ret->addIncoming(llvm::Constant::getNullValue(Str->getType()), Entry);
+    Ret->addIncoming(llvm::Constant::getNullValue(Str->getType()), Next);
+    Ret->addIncoming(FoundChr, CmpEq);
+    return RValue::get(Ret);
+  }
   case Builtin::BI__builtin_wmemcmp: {
     // The MSVC runtime library does not provide a definition of wmemcmp, so we
     // need an inline implementation.
     if (!getTarget().getTriple().isOSMSVCRT())
       break;
 
     llvm::Type *WCharTy = ConvertType(getContext().WCharTy);
 

clang/test/CodeGen/wmemchr.c

+// RUN: %clang_cc1 %s -triple x86_64-pc-win32 -emit-llvm -o - | FileCheck %s
+
+typedef __SIZE_TYPE__ size_t;
+typedef __WCHAR_TYPE__ wchar_t;
+
+const wchar_t *wmemchr_test(const wchar_t *s, const wchar_t c, size_t n) {
+  // CHECK-LABEL: define dso_local i16* @wmemchr_test
+  // CHECK: [[S:%.*]] = load
+  // CHECK: [[C:%.*]] = load
+  // CHECK: [[N:%.*]] = load
+  // CHECK: [[N0:%.*]] = icmp eq i64 [[N]], 0
+  // CHECK: br i1 [[N0]], label %[[EXIT:.*]], label %[[EQ:.*]]
+
+  // CHECK: [[EQ]]:
+  // CHECK: [[SP:%.*]] = phi i16* [ [[S]], %[[ENTRY:.*]] ], [ [[SN:.*]], %[[NEXT:.*]] ]
+  // CHECK: [[NP:%.*]] = phi i64 [ [[N]], %[[ENTRY]] ], [ [[NN:.*]], %[[NEXT]] ]
+  // CHECK: [[SL:%.*]] = load i16, i16* [[SP]], align 2
+  // CHECK: [[RES:%.*]] = getelementptr inbounds i16, i16* [[SP]], i32 0
+  // CHECK: [[CMPEQ:%.*]] = icmp eq i16 [[SL]], [[C]]
+  // CHECK: br i1 [[CMPEQ]], label %[[EXIT]], label %[[LT:.*]]
+
+  // CHECK: [[NEXT]]:
+  // CHECK: [[SN]] = getelementptr inbounds i16, i16* [[SP]], i32 1
+  // CHECK: [[NN]] = sub i64 [[NP]], 1
+  // CHECK: [[NN0:%.*]] = icmp eq i64 [[NN]], 0
+  // CHECK: br i1 [[NN0]], label %[[EXIT]], label %[[EQ]]
+  //
+  // CHECK: [[EXIT]]:
+  // CHECK: [[RV:%.*]] = phi i16* [ null, %[[ENTRY]] ], [ null, %[[NEXT]] ], [ [[RES]], %[[EQ]] ] 
+  // CHECK: ret i16* [[RV]]
+  return __builtin_wmemchr(s, c, n);
+}