[llvm] r309933 - [LiveDebugVariables] Use lexical scope to trim debug value live intervals
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 15 20:16:51 PDT 2017
Thanks! Sounds good :)
On Tue, Aug 15, 2017 at 3:52 PM Robert Lougher <rob.lougher at gmail.com>
wrote:
> Sorry for the delay, I've only just seen your reply... If the lexical
> scope is fragmented it will have more than one instruction range. The
> debug value intervals are checked against all of the ranges. Any which
> overlap the start or end of a range are trimmed to the start or end. If a
> DBG_VALUE starts outside of any range, but was live within the lexical
> scope, it must overlap the start of one of the ranges - its trimmed live
> interval would then start at the start of the range.
>
> Rob.
>
>
> On 7 August 2017 at 22:44, David Blaikie <dblaikie at gmail.com> wrote:
>
>> Out of curiosity - how does this handle cases of fragmented lexical
>> scopes? (& what if, say, the DBG_VALUE starts outside any of the fragments
>> of the lexical scope, but is live within it?)
>>
>>
>> On Thu, Aug 3, 2017 at 4:54 AM Robert Lougher via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: rlougher
>>> Date: Thu Aug 3 04:54:02 2017
>>> New Revision: 309933
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=309933&view=rev
>>> Log:
>>> [LiveDebugVariables] Use lexical scope to trim debug value live intervals
>>>
>>> The debug value live intervals computed by Live Debug Variables may
>>> extend
>>> beyond the range of the debug location's lexical scope. In this case,
>>> splitting of an interval can result in an interval outside of the scope
>>> being
>>> created, causing extra unnecessary DBG_VALUEs to be emitted. To prevent
>>> this,
>>> trim the intervals to the lexical scope.
>>>
>>> This resolves PR33730.
>>>
>>> Reviewers: aprantl
>>>
>>> Differential Revision: https://reviews.llvm.org/D35953
>>>
>>> Added:
>>> llvm/trunk/test/DebugInfo/X86/live-debug-variables.ll
>>> Modified:
>>> llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp
>>> llvm/trunk/test/DebugInfo/X86/dbg-value-dag-combine.ll
>>>
>>> Modified: llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp?rev=309933&r1=309932&r2=309933&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp (original)
>>> +++ llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp Thu Aug 3 04:54:02
>>> 2017
>>> @@ -21,7 +21,9 @@
>>>
>>> #include "LiveDebugVariables.h"
>>> #include "llvm/ADT/IntervalMap.h"
>>> +#include "llvm/ADT/SmallSet.h"
>>> #include "llvm/ADT/Statistic.h"
>>> +#include "llvm/CodeGen/LexicalScopes.h"
>>> #include "llvm/CodeGen/LiveIntervalAnalysis.h"
>>> #include "llvm/CodeGen/MachineDominators.h"
>>> #include "llvm/CodeGen/MachineFunction.h"
>>> @@ -101,6 +103,10 @@ class UserValue {
>>> /// Map of slot indices where this value is live.
>>> LocMap locInts;
>>>
>>> + /// Set of interval start indexes that have been trimmed to the
>>> + /// lexical scope.
>>> + SmallSet<SlotIndex, 2> trimmedDefs;
>>> +
>>> /// coalesceLocation - After LocNo was changed, check if it has become
>>> /// identical to another location, and coalesce them. This may cause
>>> LocNo or
>>> /// a later location to be erased, but no earlier location will be
>>> erased.
>>> @@ -229,7 +235,7 @@ public:
>>> /// computeIntervals - Compute the live intervals of all locations
>>> after
>>> /// collecting all their def points.
>>> void computeIntervals(MachineRegisterInfo &MRI, const
>>> TargetRegisterInfo &TRI,
>>> - LiveIntervals &LIS);
>>> + LiveIntervals &LIS, LexicalScopes &LS);
>>>
>>> /// splitRegister - Replace OldReg ranges with NewRegs ranges where
>>> NewRegs is
>>> /// live. Returns true if any changes were made.
>>> @@ -627,10 +633,9 @@ UserValue::addDefsFromCopies(LiveInterva
>>> }
>>> }
>>>
>>> -void
>>> -UserValue::computeIntervals(MachineRegisterInfo &MRI,
>>> - const TargetRegisterInfo &TRI,
>>> - LiveIntervals &LIS) {
>>> +void UserValue::computeIntervals(MachineRegisterInfo &MRI,
>>> + const TargetRegisterInfo &TRI,
>>> + LiveIntervals &LIS, LexicalScopes &LS)
>>> {
>>> SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
>>>
>>> // Collect all defs to be extended (Skipping undefs).
>>> @@ -672,17 +677,88 @@ UserValue::computeIntervals(MachineRegis
>>> extendDef(Idx, LocNo, LR, VNI, nullptr, LIS);
>>> }
>>>
>>> - // Finally, erase all the undefs.
>>> + // Erase all the undefs.
>>> for (LocMap::iterator I = locInts.begin(); I.valid();)
>>> if (I.value() == ~0u)
>>> I.erase();
>>> else
>>> ++I;
>>> +
>>> + // The computed intervals may extend beyond the range of the debug
>>> + // location's lexical scope. In this case, splitting of an interval
>>> + // can result in an interval outside of the scope being created,
>>> + // causing extra unnecessary DBG_VALUEs to be emitted. To prevent
>>> + // this, trim the intervals to the lexical scope.
>>> +
>>> + LexicalScope *Scope = LS.findLexicalScope(dl);
>>> + if (!Scope)
>>> + return;
>>> +
>>> + SlotIndex PrevEnd;
>>> + LocMap::iterator I = locInts.begin();
>>> +
>>> + // Iterate over the lexical scope ranges. Each time round the loop
>>> + // we check the intervals for overlap with the end of the previous
>>> + // range and the start of the next. The first range is handled as
>>> + // a special case where there is no PrevEnd.
>>> + for (const InsnRange &Range : Scope->getRanges()) {
>>> + SlotIndex RStart = LIS.getInstructionIndex(*Range.first);
>>> + SlotIndex REnd = LIS.getInstructionIndex(*Range.second);
>>> +
>>> + // At the start of each iteration I has been advanced so that
>>> + // I.stop() >= PrevEnd. Check for overlap.
>>> + if (PrevEnd && I.start() < PrevEnd) {
>>> + SlotIndex IStop = I.stop();
>>> + unsigned LocNo = I.value();
>>> +
>>> + // Stop overlaps previous end - trim the end of the interval to
>>> + // the scope range.
>>> + I.setStopUnchecked(PrevEnd);
>>> + ++I;
>>> +
>>> + // If the interval also overlaps the start of the "next" (i.e.
>>> + // current) range create a new interval for the remainder (which
>>> + // may be further trimmed).
>>> + if (RStart < IStop)
>>> + I.insert(RStart, IStop, LocNo);
>>> + }
>>> +
>>> + // Advance I so that I.stop() >= RStart, and check for overlap.
>>> + I.advanceTo(RStart);
>>> + if (!I.valid())
>>> + return;
>>> +
>>> + if (I.start() < RStart) {
>>> + // Interval start overlaps range - trim to the scope range.
>>> + I.setStartUnchecked(RStart);
>>> + // Remember that this interval was trimmed.
>>> + trimmedDefs.insert(RStart);
>>> + }
>>> +
>>> + // The end of a lexical scope range is the last instruction in the
>>> + // range. To convert to an interval we need the index of the
>>> + // instruction after it.
>>> + REnd = REnd.getNextIndex();
>>> +
>>> + // Advance I to first interval outside current range.
>>> + I.advanceTo(REnd);
>>> + if (!I.valid())
>>> + return;
>>> +
>>> + PrevEnd = REnd;
>>> + }
>>> +
>>> + // Check for overlap with end of final range.
>>> + if (PrevEnd && I.start() < PrevEnd)
>>> + I.setStopUnchecked(PrevEnd);
>>> }
>>>
>>> void LDVImpl::computeIntervals() {
>>> + LexicalScopes LS;
>>> + LS.initialize(*MF);
>>> +
>>> for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
>>> - userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS);
>>> + userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, LS);
>>> userValues[i]->mapVirtRegs(this);
>>> }
>>> }
>>> @@ -957,6 +1033,13 @@ void UserValue::emitDebugValues(VirtRegM
>>> SlotIndex Start = I.start();
>>> SlotIndex Stop = I.stop();
>>> unsigned LocNo = I.value();
>>> +
>>> + // If the interval start was trimmed to the lexical scope insert the
>>> + // DBG_VALUE at the previous index (otherwise it appears after the
>>> + // first instruction in the range).
>>> + if (trimmedDefs.count(Start))
>>> + Start = Start.getPrevIndex();
>>> +
>>> DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
>>> MachineFunction::iterator MBB =
>>> LIS.getMBBFromIndex(Start)->getIterator();
>>> SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
>>>
>>> Modified: llvm/trunk/test/DebugInfo/X86/dbg-value-dag-combine.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/dbg-value-dag-combine.ll?rev=309933&r1=309932&r2=309933&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/DebugInfo/X86/dbg-value-dag-combine.ll (original)
>>> +++ llvm/trunk/test/DebugInfo/X86/dbg-value-dag-combine.ll Thu Aug 3
>>> 04:54:02 2017
>>> @@ -5,10 +5,11 @@ target triple = "i686-apple-darwin"
>>>
>>> ; There should be a DEBUG_VALUE for each call to llvm.dbg.value
>>>
>>> -; CHECK: ##DEBUG_VALUE: __OpenCL_test_kernel:ip <-
>>> -; CHECK: ##DEBUG_VALUE: xxx <- 0
>>> -; CHECK: ##DEBUG_VALUE: gid <- %E{{..$}}
>>> -; CHECK: ##DEBUG_VALUE: idx <- %E{{..$}}
>>> +; CHECK-LABEL: __OpenCL_test_kernel:
>>> +; CHECK-DAG: ##DEBUG_VALUE: __OpenCL_test_kernel:ip <-
>>> +; CHECK-DAG: ##DEBUG_VALUE: xxx <- 0
>>> +; CHECK-DAG: ##DEBUG_VALUE: gid <- %E{{..$}}
>>> +; CHECK-DAG: ##DEBUG_VALUE: idx <- %E{{..$}}
>>> ; CHECK-NOT: ##DEBUG_VALUE:
>>>
>>> declare <4 x i32> @__amdil_get_global_id_int()
>>>
>>> Added: llvm/trunk/test/DebugInfo/X86/live-debug-variables.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/live-debug-variables.ll?rev=309933&view=auto
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/DebugInfo/X86/live-debug-variables.ll (added)
>>> +++ llvm/trunk/test/DebugInfo/X86/live-debug-variables.ll Thu Aug 3
>>> 04:54:02 2017
>>> @@ -0,0 +1,77 @@
>>> +; RUN: llc -mtriple=x86_64-linux-gnu -filetype=obj -o - %s |
>>> llvm-dwarfdump -debug-dump=loc - | FileCheck %s
>>> +
>>> +; The test inlines the function F four times, with each inlined
>>> variable for
>>> +; "i4" sharing the same virtual register. This means the live interval
>>> of the
>>> +; register spans all of the inlined callsites, extending beyond the
>>> lexical
>>> +; scope of each. Later during register allocation the live interval is
>>> split
>>> +; into multiple intervals. Check that this does not generate multiple
>>> entries
>>> +; within the debug location (see PR33730).
>>> +;
>>> +; Generated from:
>>> +;
>>> +; extern int foobar(int, int, int, int, int);
>>> +;
>>> +; int F(int i1, int i2, int i3, int i4, int i5) {
>>> +; return foobar(i1, i2, i3, i4, i5);
>>> +; }
>>> +;
>>> +; int foo(int a, int b, int c, int d, int e) {
>>> +; return F(a,b,c,d,e) +
>>> +; F(a,b,c,d,e) +
>>> +; F(a,b,c,d,e) +
>>> +; F(a,b,c,d,e);
>>> +; }
>>> +
>>> +; CHECK: Beginning address offset
>>> +; CHECK-NOT: Beginning address offset
>>> +
>>> +declare i32 @foobar(i32, i32, i32, i32, i32)
>>> +
>>> +define i32 @foo(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e) !dbg !25 {
>>> +entry:
>>> + tail call void @llvm.dbg.value(metadata i32 %d, i64 0, metadata !15,
>>> metadata !17) #3, !dbg !41
>>> + %call.i = tail call i32 @foobar(i32 %a, i32 %b, i32 %c, i32 %d, i32
>>> %e) #3, !dbg !43
>>> + %call.i21 = tail call i32 @foobar(i32 %a, i32 %b, i32 %c, i32 %d, i32
>>> %e) #3, !dbg !50
>>> + %add = add nsw i32 %call.i21, %call.i, !dbg !51
>>> + %call.i22 = tail call i32 @foobar(i32 %a, i32 %b, i32 %c, i32 %d, i32
>>> %e) #3, !dbg !58
>>> + %add3 = add nsw i32 %add, %call.i22, !dbg !59
>>> + %call.i23 = tail call i32 @foobar(i32 %a, i32 %b, i32 %c, i32 %d, i32
>>> %e) #3, !dbg !66
>>> + %add5 = add nsw i32 %add3, %call.i23, !dbg !67
>>> + ret i32 %add5, !dbg !68
>>> +}
>>> +
>>> +declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
>>> +
>>> +!llvm.dbg.cu = !{!0}
>>> +!llvm.module.flags = !{!3, !4, !5}
>>> +!llvm.ident = !{!6}
>>> +
>>> +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer:
>>> "clang version 6.0.0 (trunk 308976)", isOptimized: true, runtimeVersion: 0,
>>> emissionKind: FullDebug, enums: !2)
>>> +!1 = !DIFile(filename: "foo.c", directory: "")
>>> +!2 = !{}
>>> +!3 = !{i32 2, !"Dwarf Version", i32 4}
>>> +!4 = !{i32 2, !"Debug Info Version", i32 3}
>>> +!5 = !{i32 1, !"wchar_size", i32 4}
>>> +!6 = !{!"clang version 6.0.0 (trunk 308976)"}
>>> +!7 = distinct !DISubprogram(name: "F", scope: !1, file: !1, line: 3,
>>> type: !8, isLocal: false, isDefinition: true, scopeLine: 3, flags:
>>> DIFlagPrototyped, isOptimized: true, unit: !0, variables: !11)
>>> +!8 = !DISubroutineType(types: !9)
>>> +!9 = !{!10, !10, !10, !10, !10, !10}
>>> +!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
>>> +!11 = !{!15}
>>> +!15 = !DILocalVariable(name: "i4", arg: 4, scope: !7, file: !1, line:
>>> 3, type: !10)
>>> +!17 = !DIExpression()
>>> +!25 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 7,
>>> type: !8, isLocal: false, isDefinition: true, scopeLine: 7, flags:
>>> DIFlagPrototyped, isOptimized: true, unit: !0, variables: !26)
>>> +!26 = !{}
>>> +!38 = distinct !DILocation(line: 8, column: 10, scope: !25)
>>> +!41 = !DILocation(line: 3, column: 35, scope: !7, inlinedAt: !38)
>>> +!43 = !DILocation(line: 4, column: 10, scope: !7, inlinedAt: !38)
>>> +!45 = distinct !DILocation(line: 9, column: 10, scope: !25)
>>> +!50 = !DILocation(line: 4, column: 10, scope: !7, inlinedAt: !45)
>>> +!51 = !DILocation(line: 8, column: 23, scope: !25)
>>> +!53 = distinct !DILocation(line: 10, column: 10, scope: !25)
>>> +!58 = !DILocation(line: 4, column: 10, scope: !7, inlinedAt: !53)
>>> +!59 = !DILocation(line: 9, column: 23, scope: !25)
>>> +!61 = distinct !DILocation(line: 11, column: 10, scope: !25)
>>> +!66 = !DILocation(line: 4, column: 10, scope: !7, inlinedAt: !61)
>>> +!67 = !DILocation(line: 10, column: 23, scope: !25)
>>> +!68 = !DILocation(line: 8, column: 3, scope: !25)
>>>
>>>
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>>
>
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