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| author | David Chase <drchase@google.com> | 2018-02-13 17:39:38 -0500 |
|---|---|---|
| committer | David Chase <drchase@google.com> | 2018-04-04 22:14:29 +0000 |
| commit | dead03b7947c79112ef6c2a91843d7b10e5ebcfe (patch) | |
| tree | c86730b5e32fe6bac28ab9d3d94c5b56ee8f1f11 /src/cmd/internal/objabi | |
| parent | 619679a3971fad8ff4aa231d7942c95579ceff23 (diff) | |
| download | go-dead03b7947c79112ef6c2a91843d7b10e5ebcfe.tar.xz | |
cmd/link: process is_stmt data into dwarf line tables
To improve debugging, instructions should be annotated with
DWARF is_stmt. The DWARF default before was is_stmt=1, and
to remove "jumpy" stepping the optimizer was tagging
instructions with a no-position position, which interferes
with the accuracy of profiling information. This allows
that to be corrected, and also allows more "jumpy" positions
to be annotated with is_stmt=0 (these changes were not made
for 1.10 because of worries about further messing up
profiling).
The is_stmt values are placed in a pc-encoded table and
passed through a symbol derived from the name of the
function and processed in the linker alongside its
processing of each function's pc/line tables.
The only change in binary size is in the .debug_line tables
measured with "objdump -h --section=.debug_line go1.test"
For go1.test, these are 2614 bytes larger,
or 0.72% of the size of .debug_line,
or 0.025% of the file size.
This will increase in proportion to how much the is_stmt
flag is used (toggled).
Change-Id: Ic1f1aeccff44591ad0494d29e1a0202a3c506a7a
Reviewed-on: https://go-review.googlesource.com/93664
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Diffstat (limited to 'src/cmd/internal/objabi')
| -rw-r--r-- | src/cmd/internal/objabi/symkind.go | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/src/cmd/internal/objabi/symkind.go b/src/cmd/internal/objabi/symkind.go index ea180d0bf8..b95a0d3c70 100644 --- a/src/cmd/internal/objabi/symkind.go +++ b/src/cmd/internal/objabi/symkind.go @@ -34,6 +34,7 @@ package objabi type SymKind uint8 // Defined SymKind values. +// These are used to index into cmd/link/internal/sym/AbiSymKindToSymKind // // TODO(rsc): Give idiomatic Go names. //go:generate stringer -type=SymKind @@ -58,4 +59,7 @@ const ( SDWARFINFO SDWARFRANGE SDWARFLOC + SDWARFMISC + // Update cmd/link/internal/sym/AbiSymKindToSymKind for new SymKind values. + ) |