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cmd/compile: Avoid and filter out zero-length location-lists.

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This change avoids creating zero length location lists by
repairing an overly aggressive change in CL146718
and by explicitly checking for and filtering out any
zero-length lists that are detected (building
compiler+runtime creates a single one).

Updates #28486.

Change-Id: I01c571fee2376474c7f3038e801bd58fd9e0b820
Reviewed-on: https://go-review.googlesource.com/c/150097
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
This commit is contained in:
David Chase 2018-11-15 14:11:19 -05:00
parent 41d0dc49d2
commit 321a3d6e85
1 changed files with 12 additions and 5 deletions
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17
src/cmd/compile/internal/ssa/debug.go
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@ -881,12 +881,11 @@ func (state *debugState) buildLocationLists(blockLocs []*BlockDebug) {
for _, b := range state.f.Blocks {
state.mergePredecessors(b, blockLocs, prevBlock)
// Handle any differences among predecessor blocks and previous block (perhaps not a predecessor)
for _, varID := range state.changedVars.contents() {
state.updateVar(VarID(varID), b, BlockStart)
}
if !blockLocs[b.ID].relevant {
// Handle any differences among predecessor blocks and previous block (perhaps not a predecessor)
for _, varID := range state.changedVars.contents() {
state.updateVar(VarID(varID), b, BlockStart)
}
continue
}
@ -1019,6 +1018,14 @@ func (state *debugState) writePendingEntry(varID VarID, endBlock, endValue ID) {
// they get incomplete debug info on 32-bit platforms.
return
}
if start == end {
if state.loggingEnabled {
// Printf not logf so not gated by GOSSAFUNC; this should fire very rarely.
fmt.Printf("Skipping empty location list for %v in %s\n", state.vars[varID], state.f.Name)
}
return
}
list := state.lists[varID]
list = appendPtr(state.ctxt, list, start)
list = appendPtr(state.ctxt, list, end)