cmd/compile: don't nilcheck newobject and return values from mapaccess{1,2}
They are guaranteed to be non-nil, no point in inserting
nil checks for them.
Fixes #15390
Change-Id: I3b9a0f2319affc2139dcc446d0a56c6785ae5a86
Reviewed-on: https://go-review.googlesource.com/22291
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index ad665fb..218f720 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -1938,8 +1938,7 @@
return s.newValue2(ssa.OpLoad, n.Type, addr, s.mem())
case OIND:
- p := s.expr(n.Left)
- s.nilCheck(p)
+ p := s.exprPtr(n.Left, false, n.Lineno)
return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
case ODOT:
@@ -1952,8 +1951,7 @@
return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
case ODOTPTR:
- p := s.expr(n.Left)
- s.nilCheck(p)
+ p := s.exprPtr(n.Left, false, n.Lineno)
p = s.newValue1I(ssa.OpOffPtr, p.Type, n.Xoffset, p)
return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
@@ -2778,19 +2776,12 @@
return s.newValue2(ssa.OpPtrIndex, Ptrto(n.Left.Type.Elem()), a, i)
}
case OIND:
- p := s.expr(n.Left)
- if !bounded {
- s.nilCheck(p)
- }
- return p
+ return s.exprPtr(n.Left, bounded, n.Lineno)
case ODOT:
p := s.addr(n.Left, bounded)
return s.newValue1I(ssa.OpOffPtr, t, n.Xoffset, p)
case ODOTPTR:
- p := s.expr(n.Left)
- if !bounded {
- s.nilCheck(p)
- }
+ p := s.exprPtr(n.Left, bounded, n.Lineno)
return s.newValue1I(ssa.OpOffPtr, t, n.Xoffset, p)
case OCLOSUREVAR:
return s.newValue1I(ssa.OpOffPtr, t, n.Xoffset,
@@ -2892,6 +2883,19 @@
}
}
+// exprPtr evaluates n to a pointer and nil-checks it.
+func (s *state) exprPtr(n *Node, bounded bool, lineno int32) *ssa.Value {
+ p := s.expr(n)
+ if bounded || n.NonNil {
+ if s.f.Config.Debug_checknil() && lineno > 1 {
+ s.f.Config.Warnl(lineno, "removed nil check")
+ }
+ return p
+ }
+ s.nilCheck(p)
+ return p
+}
+
// nilCheck generates nil pointer checking code.
// Starts a new block on return, unless nil checks are disabled.
// Used only for automatically inserted nil checks,
