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DwarfDebug: Emit number of bytes in .debug_loc entry directly

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Emit the number of bytes in a `.debug_loc` entry directly.  The old code
created temp labels (expensive), emitted the difference between them,
and then emitted one on each side of the relevant bytes.

(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`
(the optimized version of ld64's `-save-temps` when linking the
`verify-uselistorder` executable in an LTO bootstrap).  I've hacked
`MCContext::Allocate()` to just call `malloc()` instead of using the
`BumpPtrAllocator` so that the heap profile is easier to read.  As far
as peak memory is concerned, `MCContext::Allocate()` is equivalent to a
leak, since it only gets freed at process teardown.

In my heap profile, this patch drops memory usage of
`DwarfDebug::emitDebugLoc()` from 132.56 MB (11.4%) down to 29.86 MB
(2.7%) at peak memory.  Some of that must be noise from `SmallVector`
(or other) allocations -- peak memory only dropped from 1160 MB down to
1100 MB -- but this nevertheless shaves 5% off the top.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236629 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2015-05-06 19:11:20 +00:00
parent 4e21d7aff9
commit 7838051bda
4 changed files with 7 additions and 20 deletions
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9
lib/CodeGen/AsmPrinter/DwarfDebug.cpp
View File

@ -1545,16 +1545,13 @@ void DebugLocEntry::finalize(const AsmPrinter &AP, DebugLocStream &Locs,
}
void DwarfDebug::emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry) {
// Emit the size.
Asm->OutStreamer->AddComment("Loc expr size");
MCSymbol *begin = Asm->OutStreamer->getContext().CreateTempSymbol();
MCSymbol *end = Asm->OutStreamer->getContext().CreateTempSymbol();
Asm->EmitLabelDifference(end, begin, 2);
Asm->OutStreamer->EmitLabel(begin);
Asm->EmitInt16(DebugLocs.getBytes(Entry).size());
// Emit the entry.
APByteStreamer Streamer(*Asm);
emitDebugLocEntry(Streamer, Entry);
// Close the range.
Asm->OutStreamer->EmitLabel(end);
}
// Emit locations into the debug loc section.

3
test/CodeGen/X86/2010-05-25-DotDebugLoc.ll
View File

@ -2,8 +2,7 @@
; RUN: llc -mtriple=x86_64-pc-linux -O2 -regalloc=basic < %s | FileCheck %s
; Test to check .debug_loc support. This test case emits many debug_loc entries.
; CHECK: .short {{.*}} # Loc expr size
; CHECK-NEXT: .Ltmp
; CHECK: .short 1 # Loc expr size
; CHECK-NEXT: DW_OP_reg
%0 = type { double }

10
test/CodeGen/X86/2010-05-26-DotDebugLoc.ll
View File

@ -77,18 +77,12 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
; CHECK-NEXT: .quad [[SET1]]
; CHECK-NEXT: [[SET2:.*]] = [[LABEL]]-Lfunc_begin0
; CHECK-NEXT: .quad [[SET2]]
; CHECK-NEXT: Lset{{.*}} = Ltmp{{.*}}-Ltmp{{.*}} ## Loc expr size
; CHECK-NEXT: .short Lset{{.*}}
; CHECK-NEXT: Ltmp{{.*}}:
; CHECK-NEXT: .short 1 ## Loc expr size
; CHECK-NEXT: .byte 85
; CHECK-NEXT: Ltmp{{.*}}:
; CHECK-NEXT: [[SET3:.*]] = [[LABEL]]-Lfunc_begin0
; CHECK-NEXT: .quad [[SET3]]
; CHECK-NEXT: [[SET4:.*]] = [[CLOBBER]]-Lfunc_begin0
; CHECK-NEXT: .quad [[SET4]]
; CHECK-NEXT: Lset{{.*}} = Ltmp{{.*}}-Ltmp{{.*}} ## Loc expr size
; CHECK-NEXT: .short Lset{{.*}}
; CHECK-NEXT: Ltmp{{.*}}:
; CHECK-NEXT: .short 1 ## Loc expr size
; CHECK-NEXT: .byte 83
; CHECK-NEXT: Ltmp{{.*}}:
!38 = !{i32 1, !"Debug Info Version", i32 3}

5
test/DebugInfo/X86/dbg-value-range.ll
View File

@ -55,11 +55,8 @@ declare void @llvm.dbg.value(metadata, i64, metadata, metadata) nounwind readnon
;CHECK-NEXT: .quad
;CHECK-NEXT: [[CLOBBER_OFF:Lset.*]] = [[CLOBBER]]-{{.*}}
;CHECK-NEXT: .quad [[CLOBBER_OFF]]
;CHECK-NEXT: Lset{{.*}} = Ltmp{{.*}}-Ltmp{{.*}}
;CHECK-NEXT: .short Lset
;CHECK-NEXT: Ltmp
;CHECK-NEXT: .short 1 ## Loc expr size
;CHECK-NEXT: .byte 85 ## DW_OP_reg
;CHECK-NEXT: Ltmp
;CHECK-NEXT: .quad 0
;CHECK-NEXT: .quad 0
!24 = !{i32 1, !"Debug Info Version", i32 3}