ConstantFold: Don't fold global address vs. null for addrspace != 0

[arsenm]

Summary

Not sure why this logic seems to be repeated in 2 different places,
one called by the other.

On AMDGPU addrspace(3) globals start allocating at 0, so these
checks will be incorrect (not that real code actually tries
to compare these addresses)

[efriedma]

LGTM

[arsenm]

r335649

[manojgupta]

In D48588#1143805, @efriedma wrote:

LGTM

Thanks, updated D47895 to include these.

lib/IR/ConstantFold.cpp

if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) &&
     if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
       return areGlobalsPotentiallyEqual(GV, GV2);
     } else if (isa<BlockAddress>(V2)) {
       return ICmpInst::ICMP_NE; // Globals never equal labels.
     } else {
       assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
       // GlobalVals can never be null unless they have external weak linkage.
       // We don't try to evaluate aliases here.
-      if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV))
+      if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV) &&
+          GV->getType()->getAddressSpace() == 0)
         return ICmpInst::ICMP_NE;
     }
   } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
     if (isa<ConstantExpr>(V2)) {  // Swap as necessary.
       ICmpInst::Predicate SwappedRelation =
         evaluateICmpRelation(V2, V1, isSigned);
       if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
         return ICmpInst::getSwappedPredicate(SwappedRelation);
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
     // and ordered comparison fails.
     return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate));
   }
 
   // icmp eq/ne(null,GV) -> false/true
   if (C1->isNullValue()) {
     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
       // Don't try to evaluate aliases.  External weak GV can be null.
-      if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
+      if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage() &&
+          GV->getType()->getAddressSpace() == 0) {
         if (pred == ICmpInst::ICMP_EQ)
           return ConstantInt::getFalse(C1->getContext());
         else if (pred == ICmpInst::ICMP_NE)
           return ConstantInt::getTrue(C1->getContext());
       }
   // icmp eq/ne(GV,null) -> false/true
   } else if (C2->isNullValue()) {
     if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
       // Don't try to evaluate aliases.  External weak GV can be null.
-      if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
+      if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage() &&
+          GV->getType()->getAddressSpace() == 0) {
         if (pred == ICmpInst::ICMP_EQ)
           return ConstantInt::getFalse(C1->getContext());
         else if (pred == ICmpInst::ICMP_NE)
           return ConstantInt::getTrue(C1->getContext());
       }
   }
 
   // If the comparison is a comparison between two i1's, simplify it.

test/Assembler/ConstantExprNoFold.ll

 @weakany = weak global i32 0
 
 ; Empty globals might end up anywhere, even on top of another global.
 ; CHECK: @empty.cmp = global i1 icmp eq ([0 x i8]* @empty.1, [0 x i8]* @empty.2)
 @empty.1 = external global [0 x i8], align 1
 @empty.2 = external global [0 x i8], align 1
 @empty.cmp = global i1 icmp eq ([0 x i8]* @empty.1, [0 x i8]* @empty.2)
 
+@addrspace3 = internal addrspace(3) global i32 undef
+
+; CHECK: @no.fold.addrspace.icmp.eq.gv.null = global i1 icmp eq (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)
+; CHECK: @no.fold.addrspace.icmp.eq.null.gv = global i1 icmp eq (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)
+; CHECK: @no.fold.addrspace.icmp.ne.gv.null = global i1 icmp ne (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)
+; CHECK: @no.fold.addrspace.icmp.ne.null.gv = global i1 icmp ne (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)
[e-mail] = global i1 icmp eq (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)
[e-mail] = global i1 icmp eq (i32 addrspace(3)* null, i32 addrspace(3)* @addrspace3)
[e-mail] = global i1 icmp ne (i32 addrspace(3)* @addrspace3, i32 addrspace(3)* null)
[e-mail] = global i1 icmp ne (i32 addrspace(3)* null, i32 addrspace(3)* @addrspace3)
+
 ; Don't add an inbounds on @glob.a3, since it's not inbounds.
 ; CHECK: @glob.a3 = alias i32, getelementptr (i32, i32* @glob.a2, i32 1)
 @glob = global i32 0
 @glob.a3 = alias i32, getelementptr (i32, i32* @glob.a2, i32 1)
 @glob.a2 = alias i32, getelementptr (i32, i32* @glob.a1, i32 1)
 @glob.a1 = alias i32, i32* @glob

test/Transforms/InstCombine/constant-fold-address-space-pointer.ll

 ; CHECK-LABEL: @constant_fold_inttoptr_null(
 ; CHECK-NEXT: ret i1 false
   %x = icmp eq i32 addrspace(3)* inttoptr (i16 99 to i32 addrspace(3)*), inttoptr (i16 0 to i32 addrspace(3)*)
   ret i1 %x
 }
 
 define i1 @constant_fold_ptrtoint_null() {
 ; CHECK-LABEL: @constant_fold_ptrtoint_null(
-; CHECK-NEXT: ret i1 false
+; CHECK-NEXT: ret i1 icmp eq (i32 addrspace(3)* @g, i32 addrspace(3)* null)
   %x = icmp eq i16 ptrtoint (i32 addrspace(3)* @g to i16), ptrtoint (i32 addrspace(3)* null to i16)
   ret i1 %x
 }
 
 define i1 @constant_fold_ptrtoint_null_2() {
 ; CHECK-LABEL: @constant_fold_ptrtoint_null_2(
-; CHECK-NEXT: ret i1 false
+; CHECK-NEXT: ret i1 icmp eq (i32 addrspace(3)* @g, i32 addrspace(3)* null)
   %x = icmp eq i16 ptrtoint (i32 addrspace(3)* null to i16), ptrtoint (i32 addrspace(3)* @g to i16)
   ret i1 %x
 }
 
 define i1 @constant_fold_ptrtoint() {
 ; CHECK-LABEL: @constant_fold_ptrtoint(
 ; CHECK-NEXT: ret i1 true
   %x = icmp eq i16 ptrtoint (i32 addrspace(3)* @g to i16), ptrtoint (i32 addrspace(3)* @g to i16)