[llvm] [LLVM][DWARF] Refactor code for generating DWARF V5 .debug_names acce… (PR #82264)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-binary-utilities

Author: None (cmtice)

<details>
<summary>Changes</summary>

…lerator table.

Refactor the code that uniques the entries and computes the bucket count for the DWARF V5 .debug_names accelerator table. This will make it easier to share this bit of code wtih other tools such as LLD.

---
Full diff: https://github.com/llvm/llvm-project/pull/82264.diff


5 Files Affected:

- (modified) llvm/include/llvm/ADT/GenericUniformityImpl.h (+1-4) 
- (modified) llvm/include/llvm/ADT/STLExtras.h (+4) 
- (modified) llvm/include/llvm/BinaryFormat/Dwarf.h (+18) 
- (modified) llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp (+2-12) 
- (modified) llvm/unittests/ADT/STLExtrasTest.cpp (+13) 


``````````diff
diff --git a/llvm/include/llvm/ADT/GenericUniformityImpl.h b/llvm/include/llvm/ADT/GenericUniformityImpl.h
index d397b937d78ccc..6b744384051b56 100644
--- a/llvm/include/llvm/ADT/GenericUniformityImpl.h
+++ b/llvm/include/llvm/ADT/GenericUniformityImpl.h
@@ -46,6 +46,7 @@
 
 #include "llvm/ADT/GenericUniformityInfo.h"
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SparseBitVector.h"
 #include "llvm/ADT/StringExtras.h"
@@ -57,10 +58,6 @@
 
 namespace llvm {
 
-template <typename Range> auto unique(Range &&R) {
-  return std::unique(adl_begin(R), adl_end(R));
-}
-
 /// Construct a specially modified post-order traversal of cycles.
 ///
 /// The ModifiedPO is contructed using a virtually modified CFG as follows:
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index a136eeb0ff1bd7..3d2f4bb40b6b79 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1994,6 +1994,10 @@ auto unique(Range &&R, Predicate P) {
   return std::unique(adl_begin(R), adl_end(R), P);
 }
 
+template <typename Range> auto unique(Range &&R) {
+  return std::unique(adl_begin(R), adl_end(R));
+}
+
 /// Wrapper function around std::equal to detect if pair-wise elements between
 /// two ranges are the same.
 template <typename L, typename R> bool equal(L &&LRange, R &&RRange) {
diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.h b/llvm/include/llvm/BinaryFormat/Dwarf.h
index 869352b35e3235..3a245972a2aa93 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.h
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.h
@@ -613,6 +613,24 @@ enum AcceleratorTable {
   DW_hash_function_djb = 0u
 };
 
+// Uniquify the string hashes and calculate the bucket count for the
+// DWARF v5 Accelerator Table.
+inline uint32_t
+ComputeDebugNamesUniqueHashes(SmallVector<uint32_t, 0> &hashes) {
+  uint32_t BucketCount = 0;
+
+  llvm::sort(hashes);
+  uint32_t uniqueHashCount = llvm::unique(hashes) - hashes.begin();
+  if (uniqueHashCount > 1024)
+    BucketCount = uniqueHashCount / 4;
+  else if (uniqueHashCount > 16)
+    BucketCount = uniqueHashCount / 2;
+  else
+    BucketCount = std::max<uint32_t>(uniqueHashCount, 1);
+
+  return BucketCount;
+}
+
 // Constants for the GNU pubnames/pubtypes extensions supporting gdb index.
 enum GDBIndexEntryKind {
   GIEK_NONE,
diff --git a/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp b/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
index 22d995a9cc3c56..7dce65d668a6de 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
@@ -33,22 +33,12 @@ using namespace llvm;
 
 void AccelTableBase::computeBucketCount() {
   // First get the number of unique hashes.
-  std::vector<uint32_t> Uniques;
+  SmallVector<uint32_t, 0> Uniques;
   Uniques.reserve(Entries.size());
   for (const auto &E : Entries)
     Uniques.push_back(E.second.HashValue);
-  array_pod_sort(Uniques.begin(), Uniques.end());
-  std::vector<uint32_t>::iterator P =
-      std::unique(Uniques.begin(), Uniques.end());
 
-  UniqueHashCount = std::distance(Uniques.begin(), P);
-
-  if (UniqueHashCount > 1024)
-    BucketCount = UniqueHashCount / 4;
-  else if (UniqueHashCount > 16)
-    BucketCount = UniqueHashCount / 2;
-  else
-    BucketCount = std::max<uint32_t>(UniqueHashCount, 1);
+  BucketCount = llvm::dwarf::ComputeDebugNamesUniqueHashes(Uniques);
 }
 
 void AccelTableBase::finalize(AsmPrinter *Asm, StringRef Prefix) {
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
index 7db339e4ef31cd..cafef5b5fad512 100644
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -1004,6 +1004,19 @@ TEST(STLExtras, Unique) {
   EXPECT_EQ(3, V[3]);
 }
 
+TEST(STLExtras, UniqueNoPred) {
+  std::vector<uint32_t> V = {1, 5, 5, 4, 3, 3, 3};
+
+  auto I = llvm::unique(V);
+
+  EXPECT_EQ(I, V.begin() + 4);
+
+  EXPECT_EQ(1, V[0]);
+  EXPECT_EQ(5, V[1]);
+  EXPECT_EQ(4, V[2]);
+  EXPECT_EQ(3, V[3]);
+}
+
 TEST(STLExtrasTest, MakeVisitorOneCallable) {
   auto IdentityLambda = [](auto X) { return X; };
   auto IdentityVisitor = makeVisitor(IdentityLambda);

``````````

</details>


https://github.com/llvm/llvm-project/pull/82264