[BuildLibCalls] Introduce getOrInsertLibFunc() for use when building libcalls.

A new set of overloaded functions named getOrInsertLibFunc() are now supposed
to be used instead of getOrInsertFunction() when building a libcall from
within an LLVM optimizer(). The idea is that this new function also makes
sure that any mandatory argument attributes are added to the function
prototype (after calling getOrInsertFunction()).

inferLibFuncAttributes() is renamed to inferNonMandatoryLibFuncAttrs() as it
only adds attributes that are not necessary for correctness but merely
helping with later optimizations.

Generally, the front end is responsible for building a correct function
prototype with the needed argument attributes. If the middle end however is
the one creating the call, e.g. when replacing one libcall with another, it
then must take this responsibility.

This continues the work of properly handling argument extension if required
by the target ABI when building a lib call. getOrInsertLibFunc() now does
this for all libcalls currently built by any LLVM optimizer. It is expected
that when in the future a new optimization builds a new libcall with an
integer argument it is to be added to getOrInsertLibFunc() with the proper
handling. Note that not all targets have it in their ABI to sign/zero extend
integer arguments to the full register width, but this will be done
selectively as determined by getExtAttrForI32Param().

Review: Eli Friedman, Nikita Popov, Dávid Bolvanský

Differential Revision: https://reviews.llvm.org/D123198

Author: JonPsson

llvm/include/llvm/IR/Module.h

@@ -363,6 +363,8 @@ class LLVM_EXTERNAL_VISIBILITY Module {
   /// In all cases, the returned value is a FunctionCallee wrapper around the
   /// 'FunctionType *T' passed in, as well as a 'Value*' either of the Function or
   /// the bitcast to the function.
+  ///
+  /// Note: For library calls getOrInsertLibFunc() should be used instead.
   FunctionCallee getOrInsertFunction(StringRef Name, FunctionType *T,
                                      AttributeList AttributeList);
 

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

@@ -22,23 +22,56 @@ namespace llvm {
   class IRBuilderBase;
 
   /// Analyze the name and prototype of the given function and set any
-  /// applicable attributes.
+  /// applicable attributes. Note that this merely helps optimizations on an
+  /// already existing function but does not consider mandatory attributes.
+  ///
   /// If the library function is unavailable, this doesn't modify it.
   ///
   /// Returns true if any attributes were set and false otherwise.
-  bool inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI);
-  bool inferLibFuncAttributes(Module *M, StringRef Name, const TargetLibraryInfo &TLI);
+  bool inferNonMandatoryLibFuncAttrs(Module *M, StringRef Name,
+                                     const TargetLibraryInfo &TLI);
+  bool inferNonMandatoryLibFuncAttrs(Function &F, const TargetLibraryInfo &TLI);
+
+  /// Calls getOrInsertFunction() and then makes sure to add mandatory
+  /// argument attributes.
+  FunctionCallee getOrInsertLibFunc(Module *M, const TargetLibraryInfo &TLI,
+                                    LibFunc TheLibFunc, FunctionType *T,
+                                    AttributeList AttributeList);
+  FunctionCallee getOrInsertLibFunc(Module *M, const TargetLibraryInfo &TLI,
+                                    LibFunc TheLibFunc, FunctionType *T);
+  template <typename... ArgsTy>
+  FunctionCallee getOrInsertLibFunc(Module *M, const TargetLibraryInfo &TLI,
+                               LibFunc TheLibFunc, AttributeList AttributeList,
+                               Type *RetTy, ArgsTy... Args) {
+    SmallVector<Type*, sizeof...(ArgsTy)> ArgTys{Args...};
+    return getOrInsertLibFunc(M, TLI, TheLibFunc,
+                              FunctionType::get(RetTy, ArgTys, false),
+                              AttributeList);
+  }
+  /// Same as above, but without the attributes.
+  template <typename... ArgsTy>
+  FunctionCallee getOrInsertLibFunc(Module *M, const TargetLibraryInfo &TLI,
+                             LibFunc TheLibFunc, Type *RetTy, ArgsTy... Args) {
+    return getOrInsertLibFunc(M, TLI, TheLibFunc, AttributeList{}, RetTy,
+                              Args...);
+  }
+  // Avoid an incorrect ordering that'd otherwise compile incorrectly.
+  template <typename... ArgsTy>
+  FunctionCallee
+  getOrInsertLibFunc(Module *M, const TargetLibraryInfo &TLI,
+                     LibFunc TheLibFunc, AttributeList AttributeList,
+                     FunctionType *Invalid, ArgsTy... Args) = delete;
 
   /// Check whether the overloaded floating point function
   /// corresponding to \a Ty is available.
   bool hasFloatFn(const TargetLibraryInfo *TLI, Type *Ty,
                   LibFunc DoubleFn, LibFunc FloatFn, LibFunc LongDoubleFn);
 
   /// Get the name of the overloaded floating point function
-  /// corresponding to \a Ty.
-  StringRef getFloatFnName(const TargetLibraryInfo *TLI, Type *Ty,
-                           LibFunc DoubleFn, LibFunc FloatFn,
-                           LibFunc LongDoubleFn);
+  /// corresponding to \a Ty. Return the LibFunc in \a TheLibFunc.
+  StringRef getFloatFn(const TargetLibraryInfo *TLI, Type *Ty,
+                       LibFunc DoubleFn, LibFunc FloatFn,
+                       LibFunc LongDoubleFn, LibFunc &TheLibFunc);
 
   /// Return V if it is an i8*, otherwise cast it to i8*.
   Value *castToCStr(Value *V, IRBuilderBase &B);
@@ -148,7 +181,8 @@ namespace llvm {
   /// function is known to take a single of type matching 'Op' and returns one
   /// value with the same type. If 'Op' is a long double, 'l' is added as the
   /// suffix of name, if 'Op' is a float, we add a 'f' suffix.
-  Value *emitUnaryFloatFnCall(Value *Op, StringRef Name, IRBuilderBase &B,
+  Value *emitUnaryFloatFnCall(Value *Op, const TargetLibraryInfo *TLI,
+                              StringRef Name, IRBuilderBase &B,
                               const AttributeList &Attrs);
 
   /// Emit a call to the unary function DoubleFn, FloatFn or LongDoubleFn,
@@ -162,8 +196,10 @@ namespace llvm {
   /// function is known to take type matching 'Op1' and 'Op2' and return one
   /// value with the same type. If 'Op1/Op2' are long double, 'l' is added as
   /// the suffix of name, if 'Op1/Op2' are float, we add a 'f' suffix.
-  Value *emitBinaryFloatFnCall(Value *Op1, Value *Op2, StringRef Name,
-                               IRBuilderBase &B, const AttributeList &Attrs);
+  Value *emitBinaryFloatFnCall(Value *Op1, Value *Op2,
+                               const TargetLibraryInfo *TLI,
+                               StringRef Name, IRBuilderBase &B,
+                               const AttributeList &Attrs);
 
   /// Emit a call to the binary function DoubleFn, FloatFn or LongDoubleFn,
   /// depending of the type of Op1.

llvm/lib/Transforms/IPO/InferFunctionAttrs.cpp

@@ -29,7 +29,7 @@ static bool inferAllPrototypeAttributes(
     // explicitly visited by CGSCC passes in the new pass manager.)
     if (F.isDeclaration() && !F.hasOptNone()) {
       if (!F.hasFnAttribute(Attribute::NoBuiltin))
-        Changed |= inferLibFuncAttributes(F, GetTLI(F));
+        Changed |= inferNonMandatoryLibFuncAttrs(F, GetTLI(F));
       Changed |= inferAttributesFromOthers(F);
     }
 

llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

@@ -1188,9 +1188,9 @@ bool LoopIdiomRecognize::processLoopStridedStore(
 
     Module *M = TheStore->getModule();
     StringRef FuncName = "memset_pattern16";
-    FunctionCallee MSP = M->getOrInsertFunction(FuncName, Builder.getVoidTy(),
-                                                Int8PtrTy, Int8PtrTy, IntIdxTy);
-    inferLibFuncAttributes(M, FuncName, *TLI);
+    FunctionCallee MSP = getOrInsertLibFunc(M, *TLI, LibFunc_memset_pattern16,
+                            Builder.getVoidTy(), Int8PtrTy, Int8PtrTy, IntIdxTy);
+    inferNonMandatoryLibFuncAttrs(M, FuncName, *TLI);
 
     // Otherwise we should form a memset_pattern16.  PatternValue is known to be
     // an constant array of 16-bytes.  Plop the value into a mergable global.