Automerge: [CaptureTracking] Handle ptrtoaddr

Unlike ptrtoint, ptrtoaddr does not capture provenance, only the address.
Note: As defined by the LangRef, we always treat `ptrtoaddr` as a
location-independent address capture since it is a direct inspection of the
pointer address.

Reviewed By: nikic

Pull Request: llvm/llvm-project#152221

Author: arichardson

llvm/lib/Analysis/CaptureTracking.cpp

@@ -359,6 +359,12 @@ UseCaptureInfo llvm::DetermineUseCaptureKind(const Use &U, const Value *Base) {
   case Instruction::AddrSpaceCast:
     // The original value is not captured via this if the new value isn't.
     return UseCaptureInfo::passthrough();
+  case Instruction::PtrToAddr:
+    // We treat ptrtoaddr as a location-independent capture of the address even
+    // if it is ultimately not used. Continuing recursive analysis after
+    // ptrtoaddr would be possible, but we'd need logic to do that correctly,
+    // which is not the same as the current pointer following logic.
+    return CaptureComponents::Address;
   case Instruction::ICmp: {
     unsigned Idx = U.getOperandNo();
     unsigned OtherIdx = 1 - Idx;

llvm/test/Transforms/FunctionAttrs/nocapture.ll

@@ -1082,6 +1082,65 @@ define i64 @captures_not_ret_only(ptr %p) {
   ret i64 %int
 }
 
+@gi = global i64 0
+
+;; Unlike ptrtoint, ptrtoaddr only captures the address
+define i64 @captures_ptrtoaddr_stored(ptr %p) {
+; FNATTRS: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(write, argmem: none, inaccessiblemem: none)
+; FNATTRS-LABEL: define noundef i64 @captures_ptrtoaddr_stored
+; FNATTRS-SAME: (ptr captures(address) [[P:%.*]]) #[[ATTR1]] {
+; FNATTRS-NEXT:    [[INT:%.*]] = ptrtoaddr ptr [[P]] to i64
+; FNATTRS-NEXT:    store i64 [[INT]], ptr @gi, align 8
+; FNATTRS-NEXT:    ret i64 0
+;
+; ATTRIBUTOR: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(write)
+; ATTRIBUTOR-LABEL: define i64 @captures_ptrtoaddr_stored
+; ATTRIBUTOR-SAME: (ptr nofree writeonly [[P:%.*]]) #[[ATTR1]] {
+; ATTRIBUTOR-NEXT:    [[INT:%.*]] = ptrtoaddr ptr [[P]] to i64
+; ATTRIBUTOR-NEXT:    store i64 [[INT]], ptr @gi, align 8
+; ATTRIBUTOR-NEXT:    ret i64 0
+;
+  %int = ptrtoaddr ptr %p to i64
+  store i64 %int, ptr @gi, align 8
+  ret i64 0
+}
+
+;; Note: ptrtoaddr is a location-independent capture, so we don't get captures(ret: address) here.
+define i64 @captures_ptrtoaddr_ret(ptr %p) {
+; FNATTRS: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; FNATTRS-LABEL: define i64 @captures_ptrtoaddr_ret
+; FNATTRS-SAME: (ptr captures(address) [[P:%.*]]) #[[ATTR0]] {
+; FNATTRS-NEXT:    [[INT:%.*]] = ptrtoaddr ptr [[P]] to i64
+; FNATTRS-NEXT:    ret i64 [[INT]]
+;
+; ATTRIBUTOR: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; ATTRIBUTOR-LABEL: define i64 @captures_ptrtoaddr_ret
+; ATTRIBUTOR-SAME: (ptr nofree readnone [[P:%.*]]) #[[ATTR0]] {
+; ATTRIBUTOR-NEXT:    [[INT:%.*]] = ptrtoaddr ptr [[P]] to i64
+; ATTRIBUTOR-NEXT:    ret i64 [[INT]]
+;
+  %int = ptrtoaddr ptr %p to i64
+  ret i64 %int
+}
+
+;; Note: ptrtoaddr is a location-independent capture, so we don't get captures(none) here.
+define i64 @captures_ptrtoaddr_ignored(ptr %p) {
+; FNATTRS: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; FNATTRS-LABEL: define noundef i64 @captures_ptrtoaddr_ignored
+; FNATTRS-SAME: (ptr captures(address) [[P:%.*]]) #[[ATTR0]] {
+; FNATTRS-NEXT:    [[INT:%.*]] = ptrtoaddr ptr [[P]] to i64
+; FNATTRS-NEXT:    ret i64 0
+;
+; ATTRIBUTOR: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn memory(none)
+; ATTRIBUTOR-LABEL: define i64 @captures_ptrtoaddr_ignored
+; ATTRIBUTOR-SAME: (ptr nofree readnone [[P:%.*]]) #[[ATTR0]] {
+; ATTRIBUTOR-NEXT:    [[INT:%.*]] = ptrtoaddr ptr [[P]] to i64
+; ATTRIBUTOR-NEXT:    ret i64 0
+;
+  %int = ptrtoaddr ptr %p to i64
+  ret i64 0
+}
+
 define void @captures_read_provenance(ptr %p) {
 ; FNATTRS-LABEL: define void @captures_read_provenance
 ; FNATTRS-SAME: (ptr captures(address, read_provenance) [[P:%.*]]) {