[AppleAccelTable] Keep track of the size of each hash data entry

In a future patch, it will be desirable to skip over all hash data entries for a
particular string. In order to do so, we must know how many bytes each of those
entries have.

In its full specification, Apple tables allow for variable length entries, which
would make the above impossible without reading the data of each entry. However,
this is largely unsupported today (as a FIXME in the code indicates, there is a
bug with hash collisions exactly because we don't know how to skip over data),
and the documentation[1] states that:

> For the current implementations of the “.apple_names” (all functions +
> globals), the “.apple_types” (names of all types that are defined), and the
> “.apple_namespaces” (all namespaces), we currently set the Atom array to be:
> [...]
> This defines the contents to be the DIE offset (eAtomTypeDIEOffset) that is
> encoded as a 32 bit value (DW_FORM_data4).

In other words, we only produce fixed sized entries.

A few tests containing invalid dwarf had to be updated, as the error is now
detected earlier (when the accelerator table is being parsed, instead of inside
the explicit call to "verify").

[1]: https://llvm.org/docs/SourceLevelDebugging.html#fixed-lookup

Depends on D152156

Differential Revision: https://reviews.llvm.org/D152157

diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
index a1f5011..c85fca4 100644 (file)
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
@@ -106,6 +106,7 @@ class AppleAcceleratorTable : public DWARFAcceleratorTable {
   Header Hdr;
   HeaderData HdrData;
   dwarf::FormParams FormParams;
+  uint32_t HashDataEntryLength;
   bool IsValid = false;
 
   /// Returns true if we should continue scanning for entries or false if we've
@@ -261,6 +262,9 @@ public:
   uint32_t getSizeHdr() const;
   uint32_t getHeaderDataLength() const;
 
+  /// Returns the size of one HashData entry.
+  uint32_t getHashDataEntryLength() const { return HashDataEntryLength; }
+
   /// Return the Atom description, which can be used to interpret the raw values
   /// of the Accelerator Entries in this table.
   ArrayRef<std::pair<HeaderData::AtomType, HeaderData::Form>> getAtomsDesc();

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
index 89b4cb9..a4aa50d 100644 (file)
--- a/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp
@@ -66,10 +66,23 @@ Error AppleAcceleratorTable::extract() {
   HdrData.DIEOffsetBase = AccelSection.getU32(&Offset);
   uint32_t NumAtoms = AccelSection.getU32(&Offset);
 
+  HashDataEntryLength = 0;
+  auto MakeUnsupportedFormError = [](dwarf::Form Form) {
+    return createStringError(errc::not_supported,
+                             "Unsupported form:" +
+                                 dwarf::FormEncodingString(Form));
+  };
+
   for (unsigned i = 0; i < NumAtoms; ++i) {
     uint16_t AtomType = AccelSection.getU16(&Offset);
     auto AtomForm = static_cast<dwarf::Form>(AccelSection.getU16(&Offset));
     HdrData.Atoms.push_back(std::make_pair(AtomType, AtomForm));
+
+    std::optional<uint8_t> FormSize =
+        dwarf::getFixedFormByteSize(AtomForm, FormParams);
+    if (!FormSize)
+      return MakeUnsupportedFormError(AtomForm);
+    HashDataEntryLength += *FormSize;
   }
 
   IsValid = true;
@@ -207,6 +220,7 @@ LLVM_DUMP_METHOD void AppleAcceleratorTable::dump(raw_ostream &OS) const {
 
   W.printNumber("DIE offset base", HdrData.DIEOffsetBase);
   W.printNumber("Number of atoms", uint64_t(HdrData.Atoms.size()));
+  W.printNumber("Size of each hash data entry", getHashDataEntryLength());
   SmallVector<DWARFFormValue, 3> AtomForms;
   {
     ListScope AtomsScope(W, "Atoms");

diff --git a/llvm/test/tools/dsymutil/X86/basic-lto-dw4-linking-x86.test b/llvm/test/tools/dsymutil/X86/basic-lto-dw4-linking-x86.test
index 867d822..15c3d87 100644 (file)
--- a/llvm/test/tools/dsymutil/X86/basic-lto-dw4-linking-x86.test
+++ b/llvm/test/tools/dsymutil/X86/basic-lto-dw4-linking-x86.test
@@ -193,6 +193,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset
@@ -286,6 +287,7 @@ CHECK-NEXT:   HeaderData length: 24
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 4
+CHECK-NEXT: Size of each hash data entry: 11
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset
@@ -342,6 +344,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset
@@ -363,6 +366,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset

diff --git a/llvm/test/tools/dsymutil/X86/basic-lto-linking-x86.test b/llvm/test/tools/dsymutil/X86/basic-lto-linking-x86.test
index 4e5d142..3fdb3bf 100644 (file)
--- a/llvm/test/tools/dsymutil/X86/basic-lto-linking-x86.test
+++ b/llvm/test/tools/dsymutil/X86/basic-lto-linking-x86.test
@@ -192,6 +192,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset
@@ -285,6 +286,7 @@ CHECK-NEXT:   HeaderData length: 24
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 4
+CHECK-NEXT: Size of each hash data entry: 11
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset
@@ -341,6 +343,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset
@@ -362,6 +365,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset

diff --git a/llvm/test/tools/dsymutil/X86/objc.test b/llvm/test/tools/dsymutil/X86/objc.test
index 47dfef5..25b02e0 100644 (file)
--- a/llvm/test/tools/dsymutil/X86/objc.test
+++ b/llvm/test/tools/dsymutil/X86/objc.test
@@ -21,6 +21,7 @@ CHECK-NEXT:   HeaderData length: 12
 CHECK-NEXT: }
 CHECK-NEXT: DIE offset base: 0
 CHECK-NEXT: Number of atoms: 1
+CHECK-NEXT: Size of each hash data entry: 4
 CHECK-NEXT: Atoms [
 CHECK-NEXT:   Atom 0 {
 CHECK-NEXT:     Type: DW_ATOM_die_offset

diff --git a/llvm/test/tools/llvm-dwarfdump/X86/apple_names_verify_form.s b/llvm/test/tools/llvm-dwarfdump/X86/apple_names_verify_form.s
index c3cc871..cf72bdc 100644 (file)
--- a/llvm/test/tools/llvm-dwarfdump/X86/apple_names_verify_form.s
+++ b/llvm/test/tools/llvm-dwarfdump/X86/apple_names_verify_form.s
@@ -3,7 +3,7 @@
 # RUN: | FileCheck %s
 
 # CHECK: Verifying .apple_names...
-# CHECK-NEXT:  error: Unsupported form: failed to read HashData.
+# CHECK-NEXT:  error: Unsupported form:
 
 # This test is meant to verify that the -verify option
 # in llvm-dwarfdump, correctly identifies that Atom[0].form is unsupported.
@@ -34,7 +34,7 @@ Lnames_begin:
        .long   0                       ## HeaderData Die Offset Base
        .long   1                       ## HeaderData Atom Count
        .short  1                       ## DW_ATOM_die_offset
-       .short  400                     ## DW_FORM_data4 -- error: unsupported form; failed to read HashData.
+       .short  400                     ## not a valid form -- error: unsupported form; failed to read HashData.
        .long   0                       ## Bucket 0
        .long   1                       ## Bucket 1
        .long   177678                  ## Hash in Bucket 0