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cmd/compile: adjust is-statement on Pos's to improve debugging

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Stores to auto tmp variables can be hoisted to places
where the line numbers make debugging look "jumpy".
Turning those instructions into ones with is_stmt = 0 in
the DWARF (accomplished by marking ssa nodes with NotStmt)
makes debugging look better while still attributing the
instructions with the correct line number.

The same is true for certain register allocator spills and
reloads.

Change-Id: I97a394eb522d4911cc40b4bf5bf76d3d7221f6c0
Reviewed-on: https://go-review.googlesource.com/98415
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
David Chase 2018-03-02 20:33:15 -05:00
parent dead03b794
commit b9a365681f
4 changed files with 34 additions and 38 deletions
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10
src/cmd/compile/internal/ssa/regalloc.go
View file

@ -444,7 +444,7 @@ func (s *regAllocState) makeSpill(v *Value, b *Block) *Value {
// *Value which is either v or a copy of v allocated to the chosen register.
func (s *regAllocState) allocValToReg(v *Value, mask regMask, nospill bool, pos src.XPos) *Value {
vi := &s.values[v.ID]
pos = pos.WithNotStmt()
// Check if v is already in a requested register.
if mask&vi.regs != 0 {
r := pickReg(mask & vi.regs)
@ -1893,18 +1893,20 @@ func (e *edgeState) process() {
fmt.Printf("breaking cycle with v%d in %s:%s\n", vid, loc, c)
}
e.erase(r)
pos := d.pos.WithNotStmt()
if _, isReg := loc.(*Register); isReg {
c = e.p.NewValue1(d.pos, OpCopy, c.Type, c)
c = e.p.NewValue1(pos, OpCopy, c.Type, c)
} else {
c = e.p.NewValue1(d.pos, OpLoadReg, c.Type, c)
c = e.p.NewValue1(pos, OpLoadReg, c.Type, c)
}
e.set(r, vid, c, false, d.pos)
e.set(r, vid, c, false, pos)
}
}
// processDest generates code to put value vid into location loc. Returns true
// if progress was made.
func (e *edgeState) processDest(loc Location, vid ID, splice **Value, pos src.XPos) bool {
pos = pos.WithNotStmt()
occupant := e.contents[loc]
if occupant.vid == vid {
// Value is already in the correct place.