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cmd/compile: use innermost line number for -S

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When functions are inlined, for instructions in the inlined body, does
-S print the location of the call, or the location of the body? Right
now, we do the former. I'd like to do the latter by default, it makes
much more sense when reading disassembly. With mid-stack inlining
enabled in more cases, this quandry will come up more often.

The original behavior is still available with -S=2. Some tests
use this mode (so they can find assembly generated by a particular
source line).

This helped me with understanding what the compiler was doing
while fixing #29007.

Change-Id: Id14a3a41e1b18901e7c5e460aa4caf6d940ed064
Reviewed-on: https://go-review.googlesource.com/c/153241
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Keith Randall 2018-12-07 10:00:36 -08:00 • committed by Keith Randall
parent ec51004567
commit 01a1eaa10c
8 changed files with 40 additions and 21 deletions
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10
src/cmd/compile/internal/gc/main.go
View file

@ -39,7 +39,6 @@ var (
var (
Debug_append int
Debug_asm bool
Debug_closure int
Debug_compilelater int
debug_dclstack int
@ -195,7 +194,7 @@ func Main(archInit func(*Arch)) {
objabi.Flagcount("K", "debug missing line numbers", &Debug['K'])
objabi.Flagcount("L", "show full file names in error messages", &Debug['L'])
objabi.Flagcount("N", "disable optimizations", &Debug['N'])
flag.BoolVar(&Debug_asm, "S", false, "print assembly listing")
objabi.Flagcount("S", "print assembly listing", &Debug['S'])
objabi.AddVersionFlag() // -V
objabi.Flagcount("W", "debug parse tree after type checking", &Debug['W'])
flag.StringVar(&asmhdr, "asmhdr", "", "write assembly header to `file`")
@ -265,7 +264,7 @@ func Main(archInit func(*Arch)) {
Ctxt.Flag_dynlink = flag_dynlink
Ctxt.Flag_optimize = Debug['N'] == 0
Ctxt.Debugasm = Debug_asm
Ctxt.Debugasm = Debug['S']
Ctxt.Debugvlog = Debug_vlog
if flagDWARF {
Ctxt.DebugInfo = debuginfo
@ -1330,6 +1329,7 @@ var concurrentFlagOK = [256]bool{
'l': true, // disable inlining
'w': true, // all printing happens before compilation
'W': true, // all printing happens before compilation
'S': true, // printing disassembly happens at the end (but see concurrentBackendAllowed below)
}
func concurrentBackendAllowed() bool {
@ -1338,9 +1338,9 @@ func concurrentBackendAllowed() bool {
return false
}
}
// Debug_asm by itself is ok, because all printing occurs
// Debug['S'] by itself is ok, because all printing occurs
// while writing the object file, and that is non-concurrent.
// Adding Debug_vlog, however, causes Debug_asm to also print
// Adding Debug_vlog, however, causes Debug['S'] to also print
// while flushing the plist, which happens concurrently.
if Debug_vlog || debugstr != "" || debuglive > 0 {
return false