[llvm] 02e8eb1 - Split getCompileUnitFor{Data,Code}Address.

[Mitch Phillips via llvm-commits]

Author: Mitch Phillips
Date: 2023-03-07T12:04:33-08:00
New Revision: 02e8eb1a438bdb1dc9a97aea75a8c9c748048039

URL: https://github.com/llvm/llvm-project/commit/02e8eb1a438bdb1dc9a97aea75a8c9c748048039
DIFF: https://github.com/llvm/llvm-project/commit/02e8eb1a438bdb1dc9a97aea75a8c9c748048039.diff

LOG: Split getCompileUnitFor{Data,Code}Address.

Getting compile units for data addresses is much slower, as it often
requires a slow fallback path to walk every DWARF entry, as
data addresses don't fall into the compilation unit ranges.

Most lookups are code addresses, and don't need this logic. Split the
functionality out so that we restore the fast-path behaviour for the
code lookups.

More context at:
https://discourse.llvm.org/t/llvm-symbolizer-has-gotten-extremely-slow/67262

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D145009

Added: 
    

Modified: 
    llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h
    llvm/lib/DebugInfo/DWARF/DWARFContext.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h
index df903b967ef68..4eba79a7215f7 100644
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h
@@ -445,7 +445,16 @@ class DWARFContext : public DIContext {
   /// address.
   /// TODO: change input parameter from "uint64_t Address"
   ///       into "SectionedAddress Address"
-  DWARFCompileUnit *getCompileUnitForAddress(uint64_t Address);
+  DWARFCompileUnit *getCompileUnitForCodeAddress(uint64_t Address);
+
+  /// Return the compile unit which contains data with the provided address.
+  /// Note: This is more expensive than `getCompileUnitForAddress`, as if
+  /// `Address` isn't found in the CU ranges (which is cheap), then it falls
+  /// back to an expensive O(n) walk of all CU's looking for data that spans the
+  /// address.
+  /// TODO: change input parameter from "uint64_t Address" into
+  ///       "SectionedAddress Address"
+  DWARFCompileUnit *getCompileUnitForDataAddress(uint64_t Address);
 
   /// Returns whether CU/TU should be populated manually. TU Index populated
   /// manually only for DWARF5.

diff  --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index dd86144d16e08..f648ef8ff7707 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -1118,14 +1118,17 @@ DWARFCompileUnit *DWARFContext::getCompileUnitForOffset(uint64_t Offset) {
       NormalUnits.getUnitForOffset(Offset));
 }
 
-DWARFCompileUnit *DWARFContext::getCompileUnitForAddress(uint64_t Address) {
-  // First, get the offset of the compile unit.
+DWARFCompileUnit *DWARFContext::getCompileUnitForCodeAddress(uint64_t Address) {
+  uint64_t CUOffset = getDebugAranges()->findAddress(Address);
+  return getCompileUnitForOffset(CUOffset);
+}
+
+DWARFCompileUnit *DWARFContext::getCompileUnitForDataAddress(uint64_t Address) {
   uint64_t CUOffset = getDebugAranges()->findAddress(Address);
-  // Retrieve the compile unit.
   if (DWARFCompileUnit *OffsetCU = getCompileUnitForOffset(CUOffset))
     return OffsetCU;
 
-  // Global variables are often not found by the above search, for one of two
+  // Global variables are often missed by the above search, for one of two
   // reasons:
   //   1. .debug_aranges may not include global variables. On clang, it seems we
   //      put the globals in the aranges, but this isn't true for gcc.
@@ -1146,7 +1149,7 @@ DWARFCompileUnit *DWARFContext::getCompileUnitForAddress(uint64_t Address) {
 DWARFContext::DIEsForAddress DWARFContext::getDIEsForAddress(uint64_t Address) {
   DIEsForAddress Result;
 
-  DWARFCompileUnit *CU = getCompileUnitForAddress(Address);
+  DWARFCompileUnit *CU = getCompileUnitForCodeAddress(Address);
   if (!CU)
     return Result;
 
@@ -1297,7 +1300,7 @@ void DWARFContext::addLocalsForDie(DWARFCompileUnit *CU, DWARFDie Subprogram,
 std::vector<DILocal>
 DWARFContext::getLocalsForAddress(object::SectionedAddress Address) {
   std::vector<DILocal> Result;
-  DWARFCompileUnit *CU = getCompileUnitForAddress(Address.Address);
+  DWARFCompileUnit *CU = getCompileUnitForCodeAddress(Address.Address);
   if (!CU)
     return Result;
 
@@ -1310,7 +1313,7 @@ DWARFContext::getLocalsForAddress(object::SectionedAddress Address) {
 DILineInfo DWARFContext::getLineInfoForAddress(object::SectionedAddress Address,
                                                DILineInfoSpecifier Spec) {
   DILineInfo Result;
-  DWARFCompileUnit *CU = getCompileUnitForAddress(Address.Address);
+  DWARFCompileUnit *CU = getCompileUnitForCodeAddress(Address.Address);
   if (!CU)
     return Result;
 
@@ -1331,7 +1334,7 @@ DILineInfo DWARFContext::getLineInfoForAddress(object::SectionedAddress Address,
 DILineInfo
 DWARFContext::getLineInfoForDataAddress(object::SectionedAddress Address) {
   DILineInfo Result;
-  DWARFCompileUnit *CU = getCompileUnitForAddress(Address.Address);
+  DWARFCompileUnit *CU = getCompileUnitForDataAddress(Address.Address);
   if (!CU)
     return Result;
 
@@ -1346,7 +1349,7 @@ DWARFContext::getLineInfoForDataAddress(object::SectionedAddress Address) {
 DILineInfoTable DWARFContext::getLineInfoForAddressRange(
     object::SectionedAddress Address, uint64_t Size, DILineInfoSpecifier Spec) {
   DILineInfoTable Lines;
-  DWARFCompileUnit *CU = getCompileUnitForAddress(Address.Address);
+  DWARFCompileUnit *CU = getCompileUnitForCodeAddress(Address.Address);
   if (!CU)
     return Lines;
 
@@ -1402,7 +1405,7 @@ DWARFContext::getInliningInfoForAddress(object::SectionedAddress Address,
                                         DILineInfoSpecifier Spec) {
   DIInliningInfo InliningInfo;
 
-  DWARFCompileUnit *CU = getCompileUnitForAddress(Address.Address);
+  DWARFCompileUnit *CU = getCompileUnitForCodeAddress(Address.Address);
   if (!CU)
     return InliningInfo;