[llvm] f65cfff - dwarfdump --statistics: Use new location list api
Pavel Labath via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 21 02:53:47 PST 2019
Author: Pavel Labath
Date: 2019-11-21T11:55:21+01:00
New Revision: f65cfff605f2fd802fc337c6152474e3f3d22a1c
URL: https://github.com/llvm/llvm-project/commit/f65cfff605f2fd802fc337c6152474e3f3d22a1c
DIFF: https://github.com/llvm/llvm-project/commit/f65cfff605f2fd802fc337c6152474e3f3d22a1c.diff
LOG: dwarfdump --statistics: Use new location list api
Summary:
This patch removes manual location list handling in the statistics code
and replaces it with the new DWARFDie api, which provides access to a
"cooked" location list. This has the following effects:
- the code now properly handles split-dwarf location lists
- it will automatically support dwarf5 location lists once support for
those is added
- it properly handles location lists with base address selection entries
- it fixes a bug where the location list code was using the first
DW_AT_ranges range as a "base address" of the compile unit (it should
have used DW_AT_low_pc instead. The effect of this was that the
computation of the start address of a variable in its scope was broken
for these kinds of compile units. This only manifested itself on
linked files, since in object files the first DW_AT_ranges range
normally starts at 0.
Since pretty much every kind of location list was broken in some way,
it's hard to verify that the new implementation is correct -- the output
will be different in all non-trivial cases, and mostly with good reason.
Most of the existing statistics tests continue to pass though, and a
visual inspection of the statistics for non-trivial inputs shows that
the data is more "reasonable" now. I have updated the "dwo statistics"
test to include the new numbers, as the previous ones were completely
bogus, and I have added a targeted test for the "base address" bug.
Reviewers: dblaikie, cmtice, vsk
Subscribers: aprantl, SouraVX, JDevlieghere, djtodoro, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70444
Added:
llvm/test/tools/llvm-dwarfdump/X86/statistics-base-address.s
Modified:
llvm/test/tools/llvm-dwarfdump/X86/statistics-dwo.test
llvm/tools/llvm-dwarfdump/Statistics.cpp
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-dwarfdump/X86/statistics-base-address.s b/llvm/test/tools/llvm-dwarfdump/X86/statistics-base-address.s
new file mode 100644
index 000000000000..9d6b762c7260
--- /dev/null
+++ b/llvm/test/tools/llvm-dwarfdump/X86/statistics-base-address.s
@@ -0,0 +1,113 @@
+# This tests the computation of the scope bytes covered by local variables. In
+# particular, the case when the variable starts in the middle of the enclosing
+# scope, and the compile unit has both DW_AT_ranges and DW_AT_low_pc attributes.
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj -o %t
+# RUN: llvm-dwarfdump --statistics %t | FileCheck %s
+
+# CHECK: "vars scope bytes total":8
+# CHECK: "vars scope bytes covered":8
+
+ .text
+
+# Add padding to ensure the function does not start at address zero.
+ .zero 256
+
+f: # @f
+.Lf_begin:
+ .zero 4
+.Lx_begin:
+ .zero 8
+.Lf_end:
+
+ .section .debug_ranges,"", at progbits
+.Ldebug_ranges:
+ .quad .Lf_begin
+ .quad .Lf_end
+ .quad 0
+ .quad 0
+
+ .section .debug_loc,"", at progbits
+.Ldebug_loc:
+ .quad .Lx_begin
+ .quad .Lf_end
+ .short 1 # Loc expr size
+ .byte 85 # super-register DW_OP_reg5
+ .quad 0
+ .quad 0
+
+
+ .section .debug_abbrev,"", at progbits
+ .byte 1 # Abbreviation Code
+ .byte 17 # DW_TAG_compile_unit
+ .byte 1 # DW_CHILDREN_yes
+ .byte 37 # DW_AT_producer
+ .byte 8 # DW_FORM_string
+ .byte 17 # DW_AT_low_pc
+ .byte 1 # DW_FORM_addr
+ .byte 85 # DW_AT_ranges
+ .byte 23 # DW_FORM_sec_offset
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 2 # Abbreviation Code
+ .byte 46 # DW_TAG_subprogram
+ .byte 1 # DW_CHILDREN_yes
+ .byte 17 # DW_AT_low_pc
+ .byte 1 # DW_FORM_addr
+ .byte 18 # DW_AT_high_pc
+ .byte 6 # DW_FORM_data4
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 3 # Abbreviation Code
+ .byte 52 # DW_TAG_variable
+ .byte 0 # DW_CHILDREN_no
+ .byte 2 # DW_AT_location
+ .byte 23 # DW_FORM_sec_offset
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 73 # DW_AT_type
+ .byte 19 # DW_FORM_ref4
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 5 # Abbreviation Code
+ .byte 36 # DW_TAG_base_type
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 62 # DW_AT_encoding
+ .byte 11 # DW_FORM_data1
+ .byte 11 # DW_AT_byte_size
+ .byte 11 # DW_FORM_data1
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 0 # EOM(3)
+
+ .section .debug_info,"", at progbits
+.Lcu_begin:
+ .long .Ldebug_info_end-.Ldebug_info_start # Length of Unit
+.Ldebug_info_start:
+ .short 4 # DWARF version number
+ .long .debug_abbrev # Offset Into Abbrev. Section
+ .byte 8 # Address Size (in bytes)
+ .byte 1 # Abbrev [1] 0xb:0x64 DW_TAG_compile_unit
+ .asciz "Hand-written DWARF" # DW_AT_producer
+ .quad 0 # DW_AT_low_pc
+ .long .Ldebug_ranges # DW_AT_ranges
+ .byte 2 # Abbrev [2] 0x2a:0x28 DW_TAG_subprogram
+ .quad .Lf_begin # DW_AT_low_pc
+ .long .Lf_end-.Lf_begin # DW_AT_high_pc
+ .asciz "f" # DW_AT_name
+ .byte 3 # Abbrev [3] 0x43:0xe DW_TAG_variable
+ .long .Ldebug_loc # DW_AT_location
+ .asciz "x" # DW_AT_name
+ .long .Lint # DW_AT_type
+ .byte 0 # End Of Children Mark
+.Lint:
+ .byte 5 # Abbrev [5] 0x67:0x7 DW_TAG_base_type
+ .asciz "int" # DW_AT_name
+ .byte 5 # DW_AT_encoding
+ .byte 4 # DW_AT_byte_size
+ .byte 0 # End Of Children Mark
+.Ldebug_info_end:
diff --git a/llvm/test/tools/llvm-dwarfdump/X86/statistics-dwo.test b/llvm/test/tools/llvm-dwarfdump/X86/statistics-dwo.test
index 8ed3537e0da8..6f9c5ee8dbbd 100644
--- a/llvm/test/tools/llvm-dwarfdump/X86/statistics-dwo.test
+++ b/llvm/test/tools/llvm-dwarfdump/X86/statistics-dwo.test
@@ -80,8 +80,8 @@ CHECK: "source variables":30
# Ideally the value below would be 33 but currently it's not.
CHECK: "variables with location":22
CHECK: "call site entries":7
-CHECK: "scope bytes total":2817
-CHECK: "scope bytes covered":506
+CHECK: "scope bytes total":2702
+CHECK: "scope bytes covered":1160
CHECK: "total function size":594
CHECK: "total inlined function size":345
CHECK: "total formal params":12
diff --git a/llvm/tools/llvm-dwarfdump/Statistics.cpp b/llvm/tools/llvm-dwarfdump/Statistics.cpp
index 8b92aab194dd..fa39e76cd4e7 100644
--- a/llvm/tools/llvm-dwarfdump/Statistics.cpp
+++ b/llvm/tools/llvm-dwarfdump/Statistics.cpp
@@ -176,7 +176,7 @@ static void collectLocStats(uint64_t BytesCovered, uint64_t BytesInScope,
}
/// Collect debug info quality metrics for one DIE.
-static void collectStatsForDie(DWARFDie Die, uint64_t UnitLowPC, std::string FnPrefix,
+static void collectStatsForDie(DWARFDie Die, std::string FnPrefix,
std::string VarPrefix, uint64_t ScopeLowPC,
uint64_t BytesInScope, uint32_t InlineDepth,
StringMap<PerFunctionStats> &FnStatMap,
@@ -243,41 +243,35 @@ static void collectStatsForDie(DWARFDie Die, uint64_t UnitLowPC, std::string FnP
return;
}
// Handle variables and function arguments.
- auto FormValue = Die.find(dwarf::DW_AT_location);
- HasLoc = FormValue.hasValue();
- if (HasLoc) {
+ Expected<std::vector<DWARFLocationExpression>> Loc =
+ Die.getLocations(dwarf::DW_AT_location);
+ if (!Loc) {
+ consumeError(Loc.takeError());
+ } else {
+ HasLoc = true;
// Get PC coverage.
- if (auto DebugLocOffset = FormValue->getAsSectionOffset()) {
- auto *DebugLoc = Die.getDwarfUnit()->getContext().getDebugLoc();
- // TODO: This code does not handle DWARF5 nor DWARF4 base address
- // selection entries. This should use a higher-level API which abstracts
- // these away.
- if (auto List = DebugLoc->getLocationListAtOffset(*DebugLocOffset)) {
- ArrayRef<DWARFLocationEntry> Entries = List->Entries;
- // Ignore end-of-list entries
- Entries = Entries.drop_back();
-
- for (auto Entry : Entries) {
- uint64_t BytesEntryCovered = Entry.Value1 - Entry.Value0;
- BytesCovered += BytesEntryCovered;
- if (IsEntryValue(Entry.Loc))
- BytesEntryValuesCovered += BytesEntryCovered;
- }
- if (Entries.size()) {
- uint64_t FirstDef = Entries[0].Value0;
- uint64_t UnitOfs = UnitLowPC;
- // Ranges sometimes start before the lexical scope.
- if (UnitOfs + FirstDef >= ScopeLowPC)
- OffsetToFirstDefinition = UnitOfs + FirstDef - ScopeLowPC;
- // Or even after it. Count that as a failure.
- if (OffsetToFirstDefinition > BytesInScope)
- OffsetToFirstDefinition = 0;
- }
- }
- assert(BytesInScope);
- } else {
+ auto Default = find_if(
+ *Loc, [](const DWARFLocationExpression &L) { return !L.Range; });
+ if (Default != Loc->end()) {
// Assume the entire range is covered by a single location.
BytesCovered = BytesInScope;
+ } else {
+ for (auto Entry : *Loc) {
+ uint64_t BytesEntryCovered = Entry.Range->HighPC - Entry.Range->LowPC;
+ BytesCovered += BytesEntryCovered;
+ if (IsEntryValue(Entry.Expr))
+ BytesEntryValuesCovered += BytesEntryCovered;
+ }
+ if (!Loc->empty()) {
+ uint64_t FirstDef = Loc->front().Range->LowPC;
+ // Ranges sometimes start before the lexical scope.
+ if (FirstDef >= ScopeLowPC)
+ OffsetToFirstDefinition = FirstDef - ScopeLowPC;
+ // Or even after it. Count that as a failure.
+ if (OffsetToFirstDefinition > BytesInScope)
+ OffsetToFirstDefinition = 0;
+ }
+ assert(BytesInScope);
}
}
}
@@ -356,7 +350,7 @@ static void collectStatsForDie(DWARFDie Die, uint64_t UnitLowPC, std::string FnP
}
/// Recursively collect debug info quality metrics.
-static void collectStatsRecursive(DWARFDie Die, uint64_t UnitLowPC, std::string FnPrefix,
+static void collectStatsRecursive(DWARFDie Die, std::string FnPrefix,
std::string VarPrefix, uint64_t ScopeLowPC,
uint64_t BytesInScope, uint32_t InlineDepth,
StringMap<PerFunctionStats> &FnStatMap,
@@ -429,7 +423,7 @@ static void collectStatsRecursive(DWARFDie Die, uint64_t UnitLowPC, std::string
}
} else {
// Not a scope, visit the Die itself. It could be a variable.
- collectStatsForDie(Die, UnitLowPC, FnPrefix, VarPrefix, ScopeLowPC, BytesInScope,
+ collectStatsForDie(Die, FnPrefix, VarPrefix, ScopeLowPC, BytesInScope,
InlineDepth, FnStatMap, GlobalStats, LocStats);
}
@@ -447,7 +441,7 @@ static void collectStatsRecursive(DWARFDie Die, uint64_t UnitLowPC, std::string
if (Child.getTag() == dwarf::DW_TAG_lexical_block)
ChildVarPrefix += toHex(LexicalBlockIndex++) + '.';
- collectStatsRecursive(Child, UnitLowPC, FnPrefix, ChildVarPrefix, ScopeLowPC,
+ collectStatsRecursive(Child, FnPrefix, ChildVarPrefix, ScopeLowPC,
BytesInScope, InlineDepth, FnStatMap, GlobalStats,
LocStats);
Child = Child.getSibling();
@@ -502,8 +496,8 @@ bool collectStatsForObjectFile(ObjectFile &Obj, DWARFContext &DICtx,
StringMap<PerFunctionStats> Statistics;
for (const auto &CU : static_cast<DWARFContext *>(&DICtx)->compile_units())
if (DWARFDie CUDie = CU->getNonSkeletonUnitDIE(false))
- collectStatsRecursive(CUDie, getLowPC(CUDie), "/", "g", 0, 0, 0,
- Statistics, GlobalStats, LocStats);
+ collectStatsRecursive(CUDie, "/", "g", 0, 0, 0, Statistics, GlobalStats,
+ LocStats);
/// The version number should be increased every time the algorithm is changed
/// (including bug fixes). New metrics may be added without increasing the
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