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cmd/compile: add ellipsis syntax for op-only rewrite rules

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This change introduces a new syntax for rewrite rules
that only change a Value's Op. See #36380 for more discussion.

Updating rewrite rules to use ellipses will happen
in follow-up CLs.

Change-Id: I8c56e85de24607579d79729575c89ca80805ba5c
Reviewed-on: https://go-review.googlesource.com/c/go/+/213898
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2020-01-07 17:18:33 -08:00
parent 0f7088ade5
commit 8484d409ac
1 changed files with 40 additions and 1 deletions
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41
src/cmd/compile/internal/ssa/gen/rulegen.go
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@ -176,6 +176,15 @@ func genRulesSuffix(arch arch, suff string) {
sw := &Switch{expr: exprf("v.Op")}
for _, op := range ops {
eop, ok := parseEllipsisRules(oprules[op], arch)
if ok {
swc := &Case{expr: exprf(op)}
swc.add(stmtf("v.Op = %s", eop))
swc.add(stmtf("return true"))
sw.add(swc)
continue
}
var ors []string
for chunk := 0; chunk < len(oprules[op]); chunk += chunkSize {
ors = append(ors, fmt.Sprintf("rewriteValue%s%s_%s_%d(v)", arch.name, suff, op, chunk))
@ -192,6 +201,11 @@ func genRulesSuffix(arch arch, suff string) {
// because it is too big for some compilers.
for _, op := range ops {
rules := oprules[op]
_, ok := parseEllipsisRules(oprules[op], arch)
if ok {
continue
}
// rr is kept between chunks, so that a following chunk checks
// that the previous one ended with a rule that wasn't
// unconditional.
@ -1240,7 +1254,7 @@ func parseValue(val string, arch arch, loc string) (op opData, oparch, typ, auxi
if x.name != s {
return false
}
if x.argLength != -1 && int(x.argLength) != len(args) {
if x.argLength != -1 && int(x.argLength) != len(args) && (len(args) != 1 || args[0] != "...") {
if strict {
return false
}
@ -1507,3 +1521,28 @@ func normalizeMatch(m string, arch arch) string {
}
return s.String()
}
func parseEllipsisRules(rules []Rule, arch arch) (newop string, ok bool) {
if len(rules) != 1 {
return "", false
}
rule := rules[0]
match, cond, result := rule.parse()
if cond != "" || !isEllipsisValue(match) || !isEllipsisValue(result) {
return "", false
}
op, oparch, _, _, _, _ := parseValue(result, arch, rule.loc)
return fmt.Sprintf("Op%s%s", oparch, op.name), true
}
// isEllipsisValue reports whether s is of the form (OpX ...).
func isEllipsisValue(s string) bool {
if len(s) < 2 || s[0] != '(' || s[len(s)-1] != ')' {
return false
}
c := split(s[1 : len(s)-1])
if len(c) != 2 || c[1] != "..." {
return false
}
return true
}