Blocks dominated by "if false" should be retained in the
initial SSA form so they remain visible to subsequent source
code analysis tools.
In any case, true compilers already need a stronger version of
this optimization so they can simplify CFGs such as this:
const x, y = ...
switch x {case y:...}
where a branch is constant but the comparison of constants
does not occur within an expression.
LGTM=gri
R=gri
CC=golang-codereviews, pcc
https://golang.org/cl/101250043
An identifier X in anonymous struct field struct{X} is both a
definition of a field (*Var) and reference to a type
(*TypeName). Now that we have split the map, we can capture
both of these aspects.
Interestingly, every client but one was going to extra effort
to iterate over just the uses or just the defs; this
simplifies them.
Also, fix two bug related to tagless switches:
- An entry was being recorded in the Object map for a piece of
synthetic syntax.
- The "true" identifier was being looked up in the current scope,
which allowed perverse users to locally redefine it. Now
we use the bool (not untyped boolean) constant true, per the
consequent clarification of the spec (issue 7404).
+ tests.
Fixesgolang/go#7276
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/68270044
Alan Donovan