From 66ed93eb73b04e7e6a91671912d0845c36b781f0 Mon Sep 17 00:00:00 2001
From: David Srbecky <dsrbecky@google.com>
Date: Wed, 14 Mar 2018 21:30:25 +0000
Subject: Cache DWARF location rules for a given pc.

Decoding the DWARF opcodes is expensive so make sure we cache it.

This speeds unwinding in simpleperf by over a factor of 3x.

Add unit tests for this new behavior.

Bug: 77258731

Test: libbacktrace/libunwindstack unit tests on host and target.
Test: Ran debuggerd -b on various processes on target.
Change-Id: Ia516c0fa5d3e5f76746190bb4b6fdf49fd1c9388
---
 libunwindstack/include/unwindstack/DwarfLocation.h | 10 +++++++++-
 libunwindstack/include/unwindstack/DwarfSection.h  |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

(limited to 'libunwindstack/include')

diff --git a/libunwindstack/include/unwindstack/DwarfLocation.h b/libunwindstack/include/unwindstack/DwarfLocation.h
index 0881182..3d50ccf 100644
--- a/libunwindstack/include/unwindstack/DwarfLocation.h
+++ b/libunwindstack/include/unwindstack/DwarfLocation.h
@@ -23,6 +23,8 @@
 
 namespace unwindstack {
 
+struct DwarfCie;
+
 enum DwarfLocationEnum : uint8_t {
   DWARF_LOCATION_INVALID = 0,
   DWARF_LOCATION_UNDEFINED,
@@ -38,7 +40,13 @@ struct DwarfLocation {
   uint64_t values[2];
 };
 
-typedef std::unordered_map<uint32_t, DwarfLocation> dwarf_loc_regs_t;
+struct DwarfLocations : public std::unordered_map<uint32_t, DwarfLocation> {
+  const DwarfCie* cie;
+  // The range of PCs where the locations are valid (end is exclusive).
+  uint64_t pc_start = 0;
+  uint64_t pc_end = 0;
+};
+typedef DwarfLocations dwarf_loc_regs_t;
 
 }  // namespace unwindstack
 
diff --git a/libunwindstack/include/unwindstack/DwarfSection.h b/libunwindstack/include/unwindstack/DwarfSection.h
index da91fd0..209c54a 100644
--- a/libunwindstack/include/unwindstack/DwarfSection.h
+++ b/libunwindstack/include/unwindstack/DwarfSection.h
@@ -20,6 +20,7 @@
 #include <stdint.h>
 
 #include <iterator>
+#include <map>
 #include <unordered_map>
 
 #include <unwindstack/DwarfError.h>
@@ -112,6 +113,7 @@ class DwarfSection {
   std::unordered_map<uint64_t, DwarfFde> fde_entries_;
   std::unordered_map<uint64_t, DwarfCie> cie_entries_;
   std::unordered_map<uint64_t, dwarf_loc_regs_t> cie_loc_regs_;
+  std::map<uint64_t, dwarf_loc_regs_t> loc_regs_;  // Single row indexed by pc_end.
 };
 
 template <typename AddressType>
-- 
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