[MemoryBuiltins] Remove isOperatorNewLike by consolidating non-null i…

…nference handling

This patch removes the isOperatorNewLike predicate since it was only being used to establish a non-null return value and we have attributes specifically for that purpose with generic handling. To keep approximate the same behaviour for existing frontends, I added the various operator new like (i.e. instances of operator new) to InferFunctionAttrs. It's not really clear to me why this isn't handled in Clang, but I didn't want to break existing code and any subtle assumptions it might have.

Once this patch is in, I'm going to start separating the isAllocLike family of predicates. These appear to be being used for a mixture of things which should be more clearly separated and documented. Today, they're being used to indicate (at least) aliasing facts, CSE-ability, and default values from an allocation site.

Differential Revision: http://reviews.llvm.org/D15820



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256787 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/MemoryBuiltins.h

@@ -59,11 +59,6 @@ bool isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 bool isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                    bool LookThroughBitCast = false);
 
-/// \brief Tests if a value is a call or invoke to a library function that
-/// allocates memory and never returns null (such as operator new).
-bool isOperatorNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
-                         bool LookThroughBitCast = false);
-
 //===----------------------------------------------------------------------===//
 //  malloc Call Utility Functions.
 //

lib/Analysis/MemoryBuiltins.cpp

@@ -187,13 +187,6 @@ bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
   return getAllocationData(V, AllocLike, TLI, LookThroughBitCast);
 }
 
-/// \brief Tests if a value is a call or invoke to a library function that
-/// allocates memory and never returns null (such as operator new).
-bool llvm::isOperatorNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
-                               bool LookThroughBitCast) {
-  return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast);
-}
-
 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 /// ignore InvokeInst here.

lib/Analysis/ValueTracking.cpp

@@ -3480,10 +3480,6 @@ bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
     if (CS.isReturnNonNull())
       return true;
 
-  // operator new never returns null.
-  if (isOperatorNewLikeFn(V, TLI, /*LookThroughBitCast=*/true))
-    return true;
-
   return false;
 }
 

lib/Transforms/IPO/InferFunctionAttrs.cpp

@@ -10,6 +10,7 @@
 #include "llvm/Transforms/IPO/InferFunctionAttrs.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
@@ -25,6 +26,7 @@ STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
 STATISTIC(NumNoCapture, "Number of arguments inferred as nocapture");
 STATISTIC(NumReadOnlyArg, "Number of arguments inferred as readonly");
 STATISTIC(NumNoAlias, "Number of function returns inferred as noalias");
+STATISTIC(NumNonNull, "Number of function returns inferred as nonnull returns");
 
 static bool setDoesNotAccessMemory(Function &F) {
   if (F.doesNotAccessMemory())
@@ -74,6 +76,17 @@ static bool setDoesNotAlias(Function &F, unsigned n) {
   return true;
 }
 
+static bool setNonNull(Function &F, unsigned n) {
+  assert((n != AttributeSet::ReturnIndex ||
+          F.getReturnType()->isPointerTy()) &&
+         "nonnull applies only to pointers");
+  if (F.getAttributes().hasAttribute(n, Attribute::NonNull))
+    return false;
+  F.addAttribute(n, Attribute::NonNull);
+  ++NumNonNull;
+  return true;
+}
+
 /// Analyze the name and prototype of the given function and set any applicable
 /// attributes.
 ///
@@ -89,7 +102,6 @@ static bool inferPrototypeAttributes(Function &F,
     return false;
 
   bool Changed = false;
-
   switch (TheLibFunc) {
   case LibFunc::strlen:
     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
@@ -873,6 +885,21 @@ static bool inferPrototypeAttributes(Function &F,
     Changed |= setDoesNotCapture(F, 2);
     return Changed;
 
+  case LibFunc::Znwj: // new(unsigned int)
+  case LibFunc::Znwm: // new(unsigned long)
+  case LibFunc::Znaj: // new[](unsigned int)
+  case LibFunc::Znam: // new[](unsigned long)
+  case LibFunc::msvc_new_int: // new(unsigned int)
+  case LibFunc::msvc_new_longlong: // new(unsigned long long)
+  case LibFunc::msvc_new_array_int: // new[](unsigned int)
+  case LibFunc::msvc_new_array_longlong: // new[](unsigned long long)
+    if (FTy->getNumParams() != 1)
+      return false;
+    // Operator new always returns a nonnull noalias pointer
+    Changed |= setNonNull(F, AttributeSet::ReturnIndex);
+    Changed |= setDoesNotAlias(F, AttributeSet::ReturnIndex);
+    return Changed;
+
   default:
     // FIXME: It'd be really nice to cover all the library functions we're
     // aware of here.

test/Transforms/InferFunctionAttrs/annotate.ll

@@ -16,6 +16,12 @@ declare i32* @realloc(i32*, i32)
 declare i32 @strcpy(...)
 ; CHECK: declare i32 @strcpy(...)
 
+; operator new routines
+declare i8* @_Znwj(i64)
+; CHECK: declare noalias nonnull i8* @_Znwj(i64)
+declare i8* @_Znwm(i64)
+; CHECK: declare noalias nonnull i8* @_Znwm(i64)
+
 declare i32 @gettimeofday(i8*, i8*)
 ; CHECK-POSIX: declare i32 @gettimeofday(i8* nocapture, i8* nocapture) [[G0:#[0-9]+]]
 

test/Transforms/InstSimplify/call.ll

@@ -144,7 +144,7 @@ cast.end:                                         ; preds = %cast.notnull, %entr
 ; CHECK: br i1 false, label %cast.end, label %cast.notnull
 }
 
-declare noalias i8* @_Znwm(i64)
+declare nonnull noalias i8* @_Znwm(i64)
 
 %"struct.std::nothrow_t" = type { i8 }
 @_ZSt7nothrow = external global %"struct.std::nothrow_t"