Commit 05a47706 authored by Nikita Popov's avatar Nikita Popov
Browse files

[ConstantFold] Fix incorrect type assumptions 

If a pointer isn't a constant expression, global or block address,
it's not guaranteed to be a null pointer. It can also be a no_cfi
or dso_local_equivalent constant.
parent 236197a0

llvm/lib/IR/ConstantFold.cpp

+4 −10
Original line number Diff line number Diff line
@@ -1172,30 +1172,24 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2) { 
  }



  if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {

    // Now we know that the RHS is a BlockAddress or simple

    // constant (which, since the types must match, means that it is a

    // ConstantPointerNull).

    // Now we know that the RHS is a BlockAddress or simple constant.

    if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {

      // Block address in another function can't equal this one, but block

      // addresses in the current function might be the same if blocks are

      // empty.

      if (BA2->getFunction() != BA->getFunction())

        return ICmpInst::ICMP_NE;

    } else {

      // Block addresses aren't null.

      assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");

    } else if (isa<ConstantPointerNull>(V2)) {

      return ICmpInst::ICMP_NE;

    }

  } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {

    // Now we know that the RHS is a GlobalValue, BlockAddress or simple

    // constant (which, since the types must match, means that it's a

    // ConstantPointerNull).

    // constant.

    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!");

    } else if (isa<ConstantPointerNull>(V2)) {

      // GlobalVals can never be null unless they have external weak linkage.

      // We don't try to evaluate aliases here.

      // NOTE: We should not be doing this constant folding if null pointer

llvm/test/Transforms/InstSimplify/ConstProp/icmp-global.ll

+23 −0
Original line number Diff line number Diff line
@@ -275,3 +275,26 @@ define i1 @global_gep_ugt_global_gep_complex() { 
  %cmp = icmp ugt ptr %gep3, @g

  ret i1 %cmp

}



declare void @func()



define i1 @global_no_cfi() {

; CHECK-LABEL: @global_no_cfi(

; CHECK-NEXT:    ret i1 icmp eq (ptr @func, ptr no_cfi @func)

;

  %cmp = icmp eq ptr @func, no_cfi @func

  ret i1 %cmp

}



define i1 @blockaddr_no_cfi() {

; CHECK-LABEL: @blockaddr_no_cfi(

; CHECK-NEXT:    br label [[BB:%.*]]

; CHECK:       bb:

; CHECK-NEXT:    ret i1 icmp eq (ptr blockaddress(@blockaddr_no_cfi, [[BB]]), ptr no_cfi @func)

;

  br label %bb



bb:

  %cmp = icmp eq ptr blockaddress(@blockaddr_no_cfi, %bb), no_cfi @func

  ret i1 %cmp

}