llvm: Add support for "-fno-delete-null-pointer-checks"

Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.

More details : https://lkml.org/lkml/2018/4/4/601

GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.

-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.

This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.

Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv

Reviewed By: efriedma, george.burgess.iv

Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits

Differential Revision: https://reviews.llvm.org/D47895

llvm-svn: 336613

1 files changed, 9 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 38e018f6db0..a49007ee499 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1589,7 +1589,8 @@ double getValueAsDouble(ConstantFP *Op) {
 
 Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
                                  ArrayRef<Constant *> Operands,
-                                 const TargetLibraryInfo *TLI) {
+                                 const TargetLibraryInfo *TLI,
+                                 ImmutableCallSite CS) {
   if (Operands.size() == 1) {
     if (isa<UndefValue>(Operands[0])) {
       // cosine(arg) is between -1 and 1. cosine(invalid arg) is NaN
@@ -1603,7 +1604,8 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
     }
 
     if (isa<ConstantPointerNull>(Operands[0]) &&
-        Operands[0]->getType()->getPointerAddressSpace() == 0) {
+        !NullPointerIsDefined(
+            CS.getCaller(), Operands[0]->getType()->getPointerAddressSpace())) {
       // launder(null) == null == strip(null) iff in addrspace 0
       if (IntrinsicID == Intrinsic::launder_invariant_group ||
           IntrinsicID == Intrinsic::strip_invariant_group)
@@ -2007,7 +2009,8 @@ Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID, Type *Ty,
 Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID,
                                  VectorType *VTy, ArrayRef<Constant *> Operands,
                                  const DataLayout &DL,
-                                 const TargetLibraryInfo *TLI) {
+                                 const TargetLibraryInfo *TLI,
+                                 ImmutableCallSite CS) {
   SmallVector<Constant *, 4> Result(VTy->getNumElements());
   SmallVector<Constant *, 4> Lane(Operands.size());
   Type *Ty = VTy->getElementType();
@@ -2070,7 +2073,7 @@ Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID,
     }
 
     // Use the regular scalar folding to simplify this column.
-    Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI);
+    Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI, CS);
     if (!Folded)
       return nullptr;
     Result[I] = Folded;
@@ -2095,9 +2098,9 @@ llvm::ConstantFoldCall(ImmutableCallSite CS, Function *F,
 
   if (auto *VTy = dyn_cast<VectorType>(Ty))
     return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands,
-                                  F->getParent()->getDataLayout(), TLI);
+                                  F->getParent()->getDataLayout(), TLI, CS);
 
-  return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI);
+  return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI, CS);
 }
 
 bool llvm::isMathLibCallNoop(CallSite CS, const TargetLibraryInfo *TLI) {