[Attributor] Fix callsite check in AAUndefinedBehavior

[okura]

Summary

This is the next patch of D86842
When we check noundef attribute violation at callsites, we do not have to require nonnull in the following two cases.

1. An argument is known to be simplified to undef
2. An argument is known to be dead

[okura]

delete unnecessary brackets

[okura]

add test

[jdoerfert]

LGTM

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

2050

While you are here, move the isa into the conditional above. No need to create/query an AA if it's not a nullptr.

[okura]

address comment

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

auto InspectCallSiteForUB = [&](Instruction &I) {
         // corresponding argument position is known to have nonnull attribute,
         // the argument is poison. Furthermore, if the argument is poison and
         // the position is known to have noundef attriubte, this callsite is
         // considered UB.
         // TODO: Check also nopoison attribute if it is introduced.
         if (idx >= Callee->arg_size())
           break;
         Value *ArgVal = CB.getArgOperand(idx);
-        if (!ArgVal || !ArgVal->getType()->isPointerTy())
+        if (!ArgVal)
           continue;
+        // Here, we handle three cases.
+        //   (1) Not having a value means it is dead. (we can replace the value
+        //       with undef)
+        //   (2) Simplified to undef. The argument violate noundef attriubte.
+        //   (3) Simplified to null pointer where known to be nonnull.
+        //       The argument is a poison value and violate noundef attribute.
         IRPosition CalleeArgumentIRP = IRPosition::callsite_argument(CB, idx);
         if (!CalleeArgumentIRP.hasAttr({Attribute::NoUndef}))
           continue;
-        auto &NonNullAA = A.getAAFor<AANonNull>(*this, CalleeArgumentIRP,
-                                                /* TrackDependence */ false);
-        if (!NonNullAA.isKnownNonNull())
-          continue;
-        const auto &ValueSimplifyAA = A.getAAFor<AAValueSimplify>(
+        auto &ValueSimplifyAA = A.getAAFor<AAValueSimplify>(
             *this, IRPosition::value(*ArgVal), /* TrackDependence */ false);
-        Optional<Value *> SimplifiedVal =
-            ValueSimplifyAA.getAssumedSimplifiedValue(A);
-
         if (!ValueSimplifyAA.isKnown())
           continue;
-        // Here, we handle three cases.
-        //   (1) Not having a value means it is dead. (we can replace the value
-        //       with undef)
-        //   (2) Simplified to null pointer. The argument is a poison value and
-        //       violate noundef attribute.
-        //   (3) Simplified to undef. The argument violate noundef attriubte.
+        Optional<Value *> SimplifiedVal =
+            ValueSimplifyAA.getAssumedSimplifiedValue(A);
         if (!SimplifiedVal.hasValue() ||
-            isa<ConstantPointerNull>(*SimplifiedVal.getValue()) ||
             isa<UndefValue>(*SimplifiedVal.getValue())) {
           KnownUBInsts.insert(&I);
-          return true;
+          continue;
         }
+        if (!ArgVal->getType()->isPointerTy() ||
+            !isa<ConstantPointerNull>(*SimplifiedVal.getValue()))
+          continue;
+        auto &NonNullAA = A.getAAFor<AANonNull>(*this, CalleeArgumentIRP,
+                                                /* TrackDependence */ false);
+        if (NonNullAA.isKnownNonNull())
+          KnownUBInsts.insert(&I);
       }
       return true;
     };
 
     auto InspectReturnInstForUB =
         [&](Value &V, const SmallSetVector<ReturnInst *, 4> RetInsts) {
           // Check if a return instruction always cause UB or not
           // Note: It is guaranteed that the returned position of the anchor

llvm/test/Transforms/Attributor/undefined_behavior.ll

 
 define void @callsite_noundef_2() {
 ; CHECK-LABEL: define {{[^@]+}}@callsite_noundef_2() {
 ; CHECK-NEXT:    unreachable
 ;
   call void @callee_ptr_arg(i32* noundef undef)
   ret void
 }
+
+define i32 @argument_noundef1(i32 noundef %c) {
+; IS__TUNIT____: Function Attrs: nofree nosync nounwind readnone willreturn
+; IS__TUNIT____-LABEL: define {{[^@]+}}@argument_noundef1
+; IS__TUNIT____-SAME: (i32 noundef returned [[C:%.*]]) [[ATTR0]] {
+; IS__TUNIT____-NEXT:    ret i32 [[C]]
+;
+; IS__CGSCC____: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
+; IS__CGSCC____-LABEL: define {{[^@]+}}@argument_noundef1
+; IS__CGSCC____-SAME: (i32 noundef returned [[C:%.*]]) [[ATTR0]] {
+; IS__CGSCC____-NEXT:    ret i32 [[C]]
+;
+  ret i32 %c
+}
+
+define i32 @violate_noundef_nonpointer() {
+; IS__TUNIT____: Function Attrs: nofree nosync nounwind readnone willreturn
+; IS__TUNIT____-LABEL: define {{[^@]+}}@violate_noundef_nonpointer
+; IS__TUNIT____-SAME: () [[ATTR0]] {
+; IS__TUNIT____-NEXT:    unreachable
+;
+; IS__CGSCC____: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
+; IS__CGSCC____-LABEL: define {{[^@]+}}@violate_noundef_nonpointer
+; IS__CGSCC____-SAME: () [[ATTR0]] {
+; IS__CGSCC____-NEXT:    unreachable
+;
+  %ret = call i32 @argument_noundef1(i32 undef)
+  ret i32 %ret
+}
+
+define i32* @argument_noundef2(i32* noundef %c) {
+; IS__TUNIT____: Function Attrs: nofree nosync nounwind readnone willreturn
+; IS__TUNIT____-LABEL: define {{[^@]+}}@argument_noundef2
+; IS__TUNIT____-SAME: (i32* nofree noundef readnone returned "no-capture-maybe-returned" [[C:%.*]]) [[ATTR0]] {
+; IS__TUNIT____-NEXT:    ret i32* [[C]]
+;
+; IS__CGSCC____: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
+; IS__CGSCC____-LABEL: define {{[^@]+}}@argument_noundef2
+; IS__CGSCC____-SAME: (i32* nofree noundef readnone returned "no-capture-maybe-returned" [[C:%.*]]) [[ATTR0]] {
+; IS__CGSCC____-NEXT:    ret i32* [[C]]
+;
+  ret i32* %c
+}
+
+define i32* @violate_noundef_pointer() {
+; IS__TUNIT____: Function Attrs: nofree nosync nounwind readnone willreturn
+; IS__TUNIT____-LABEL: define {{[^@]+}}@violate_noundef_pointer
+; IS__TUNIT____-SAME: () [[ATTR0]] {
+; IS__TUNIT____-NEXT:    unreachable
+;
+; IS__CGSCC____: Function Attrs: nofree norecurse nosync nounwind readnone willreturn
+; IS__CGSCC____-LABEL: define {{[^@]+}}@violate_noundef_pointer
+; IS__CGSCC____-SAME: () [[ATTR0]] {
+; IS__CGSCC____-NEXT:    unreachable
+;
+  %ret = call i32* @argument_noundef2(i32* undef)
+  ret i32* %ret
+}