[PATCH] D137028: [llvm][utils] Add DenseMap data formatters (WIP)

[Dave Lee via Phabricator via llvm-commits]

kastiglione updated this revision to Diff 474637.
kastiglione added a comment.

Fix summary provider by working with the non-synthetic value


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137028/new/

https://reviews.llvm.org/D137028

Files:
  llvm/utils/lldbDataFormatters.py


Index: llvm/utils/lldbDataFormatters.py
===================================================================
--- llvm/utils/lldbDataFormatters.py
+++ llvm/utils/lldbDataFormatters.py
@@ -4,8 +4,11 @@
 Load into LLDB with 'command script import /path/to/lldbDataFormatters.py'
 """
 
+import collections
 import lldb
 import json
+from typing import Optional
+
 
 def __lldb_init_module(debugger, internal_dict):
     debugger.HandleCommand('type category define -e llvm -l c++')
@@ -48,6 +51,12 @@
     debugger.HandleCommand('type synthetic add -w llvm '
                            '-l lldbDataFormatters.PointerUnionSynthProvider '
                            '-x "^llvm::PointerUnion<.+>$"')
+    debugger.HandleCommand('type summary add -w llvm '
+                           '-e -F lldbDataFormatters.DenseMapSummary '
+                           '-x "^llvm::DenseMap<.+>$"')
+    debugger.HandleCommand('type synthetic add -w llvm '
+                           '-l lldbDataFormatters.DenseMapSynthetic '
+                           '-x "^llvm::DenseMap<.+>$"')
 
 
 # Pretty printer for llvm::SmallVector/llvm::SmallVectorImpl
@@ -291,3 +300,68 @@
         self.val_expr_path = get_expression_path(self.valobj.GetChildMemberWithName('Val'))
         self.active_type_tag = self.valobj.CreateValueFromExpression('', f'(int){self.val_expr_path}.getInt()').GetValueAsSigned()
         self.template_args = parse_template_parameters(self.valobj.GetType().name)
+
+
+def DenseMapSummary(valobj: lldb.SBValue, _) -> str:
+    num_entries = valobj.GetNonSyntheticValue().GetChildMemberWithName("NumEntries")
+    return f"size={num_entries.unsigned}"
+
+
+class DenseMapSynthetic:
+    valobj: lldb.SBValue
+
+    # The bucket indexes containing child values.
+    child_buckets: list[int]
+
+    def __init__(self, valobj: lldb.SBValue, _) -> None:
+        self.valobj = valobj
+
+    def num_children(self) -> int:
+        return len(self.child_buckets)
+
+    def get_child_at_index(self, child_index: int) -> Optional[lldb.SBValue]:
+        bucket_index = self.child_buckets[child_index]
+        entry = self.valobj.GetValueForExpressionPath(f".Buckets[{bucket_index}]")
+
+        # By default, DenseMap instances use DenseMapPair to hold key-value
+        # entries. This type can be customized (it's a template parameter). If
+        # the entry is a DenseMapPair, unwrap it to expose the child entries as
+        # simple std::pair values. Otherwise, use the entry as is.
+        if entry.type.name.startswith("llvm::detail::DenseMapPair<"):
+            entry = entry.GetChildAtIndex(0)
+
+        return entry.Clone(f"[{child_index}]")
+
+    def update(self) -> bool:
+        self.child_buckets = []
+
+        num_entries = self.valobj.GetChildMemberWithName("NumEntries").unsigned
+        if num_entries == 0:
+            return
+
+        buckets = self.valobj.GetChildMemberWithName("Buckets")
+        num_buckets = self.valobj.GetChildMemberWithName("NumBuckets").unsigned
+
+        # Bucket entries contain one of the following:
+        #   1. Valid key-value
+        #   2. Empty key
+        #   3. Tombstone key (marks a deleted value)
+        #
+        # NumBuckets is always greater than NumEntries. The empty key, and
+        # potentially the tombstone key, will occur multiple times. A key that
+        # is repeated is either the empty key or the tombstone key.
+
+        # For each key, collect a list of buckets it appears in.
+        key_buckets: dict[str, list[int]] = collections.defaultdict(list)
+        for index in range(num_buckets):
+            key = buckets.GetValueForExpressionPath(f"[{index}].first")
+            key_buckets[str(key.data)].append(index)
+
+        # Heuristic: Repeated (non-unique) keys are either the the empty key or
+        # the tombstone key. Populate child_buckets with the bucket indexes of
+        # entries containing unique keys.
+        for indexes in key_buckets.values():
+            if len(indexes) == 1:
+                self.child_buckets.append(indexes[0])
+
+        return True


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