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cmd/compile: add compiler debug flag to disable range func iterator checking

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E.g.
`GOEXPERIMENT=rangefunc go test -v -gcflags=-d=rangefunccheck=0 rangefunc_test.go`
will turn off the checking and fail.

The benchmarks, which do not use pathological iterators, run slightly faster.

Change-Id: Ia3e175e86d67ef74bbae9bcc5d2def6a2cdf519d
Reviewed-on: https://go-review.googlesource.com/c/go/+/541995
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
David Chase 2023-11-11 15:32:45 -05:00
parent d6ef98b8fa
commit d411b3197c
3 changed files with 40 additions and 11 deletions
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1
src/cmd/compile/internal/base/debug.go
View File

@ -60,6 +60,7 @@ type DebugFlags struct {
PGOInlineCDFThreshold string `help:"cumulative threshold percentage for determining call sites as hot candidates for inlining" concurrent:"ok"`
PGOInlineBudget int `help:"inline budget for hot functions" concurrent:"ok"`
PGODevirtualize int `help:"enable profile-guided devirtualization" concurrent:"ok"`
RangeFuncCheck int `help:"insert code to check behavior of range iterator functions" concurrent:"ok"`
WrapGlobalMapDbg int `help:"debug trace output for global map init wrapping"`
WrapGlobalMapCtl int `help:"global map init wrap control (0 => default, 1 => off, 2 => stress mode, no size cutoff)"`
ZeroCopy int `help:"enable zero-copy string->[]byte conversions" concurrent:"ok"`

1
src/cmd/compile/internal/base/flag.go
View File

@ -182,6 +182,7 @@ func ParseFlags() {
Debug.PGODevirtualize = 1
Debug.SyncFrames = -1 // disable sync markers by default
Debug.ZeroCopy = 1
Debug.RangeFuncCheck = 1
Debug.Checkptr = -1 // so we can tell whether it is set explicitly

49
src/cmd/compile/internal/rangefunc/rewrite.go
View File

@ -554,6 +554,11 @@ func rewriteFunc(pkg *types2.Package, info *types2.Info, typ *syntax.FuncType, b
}
}
// checkFuncMisuse reports whether to check for misuse of iterator callbacks functions.
func (r *rewriter) checkFuncMisuse() bool {
return base.Debug.RangeFuncCheck != 0
}
// inspect is a callback for syntax.Inspect that drives the actual rewriting.
// If it sees a func literal, it kicks off a separate rewrite for that literal.
// Otherwise, it maintains a stack of range-over-func loops and
@ -621,7 +626,10 @@ func (r *rewriter) startLoop(loop *forLoop) {
r.false = types2.Universe.Lookup("false")
r.rewritten = make(map[*syntax.ForStmt]syntax.Stmt)
}
loop.exitFlag, loop.exitFlagDecl = r.exitVar(loop.nfor.Pos())
if r.checkFuncMisuse() {
// declare the exit flag for this loop's body
loop.exitFlag, loop.exitFlagDecl = r.exitVar(loop.nfor.Pos())
}
}
// editStmt returns the replacement for the statement x,
@ -714,8 +722,11 @@ func (r *rewriter) editReturn(x *syntax.ReturnStmt) syntax.Stmt {
bl.List = append(bl.List, &syntax.AssignStmt{Lhs: r.useList(r.retVars), Rhs: x.Results})
}
bl.List = append(bl.List, &syntax.AssignStmt{Lhs: r.next(), Rhs: r.intConst(next)})
for i := 0; i < len(r.forStack); i++ {
bl.List = append(bl.List, r.setExitedAt(i))
if r.checkFuncMisuse() {
// mark all enclosing loop bodies as exited
for i := 0; i < len(r.forStack); i++ {
bl.List = append(bl.List, r.setExitedAt(i))
}
}
bl.List = append(bl.List, &syntax.ReturnStmt{Results: r.useVar(r.false)})
setPos(bl, x.Pos())
@ -811,8 +822,14 @@ func (r *rewriter) editBranch(x *syntax.BranchStmt) syntax.Stmt {
// If this is a simple break, mark this loop as exited and return false.
// No adjustments to #next.
if depth == 0 {
var stmts []syntax.Stmt
if r.checkFuncMisuse() {
stmts = []syntax.Stmt{r.setExited(), ret}
} else {
stmts = []syntax.Stmt{ret}
}
bl := &syntax.BlockStmt{
List: []syntax.Stmt{r.setExited(), ret},
List: stmts,
}
setPos(bl, x.Pos())
return bl
@ -846,9 +863,11 @@ func (r *rewriter) editBranch(x *syntax.BranchStmt) syntax.Stmt {
List: []syntax.Stmt{as},
}
// Set #exitK for this loop and those exited by the control flow.
for i := exitFrom; i < len(r.forStack); i++ {
bl.List = append(bl.List, r.setExitedAt(i))
if r.checkFuncMisuse() {
// Set #exitK for this loop and those exited by the control flow.
for i := exitFrom; i < len(r.forStack); i++ {
bl.List = append(bl.List, r.setExitedAt(i))
}
}
bl.List = append(bl.List, ret)
@ -953,12 +972,18 @@ func (r *rewriter) endLoop(loop *forLoop) {
}
// declare the exitFlag here so it has proper scope and zeroing
exitFlagDecl := &syntax.DeclStmt{DeclList: []syntax.Decl{loop.exitFlagDecl}}
block.List = append(block.List, exitFlagDecl)
if r.checkFuncMisuse() {
exitFlagDecl := &syntax.DeclStmt{DeclList: []syntax.Decl{loop.exitFlagDecl}}
block.List = append(block.List, exitFlagDecl)
}
// iteratorFunc(bodyFunc)
block.List = append(block.List, call)
block.List = append(block.List, r.setExited())
if r.checkFuncMisuse() {
// iteratorFunc has exited, mark the exit flag for the body
block.List = append(block.List, r.setExited())
}
block.List = append(block.List, checks...)
if len(r.forStack) == 1 { // ending an outermost loop
@ -1037,7 +1062,9 @@ func (r *rewriter) bodyFunc(body []syntax.Stmt, lhs []syntax.Expr, def bool, fty
loop := r.forStack[len(r.forStack)-1]
bodyFunc.Body.List = append(bodyFunc.Body.List, r.assertNotExited(start, loop))
if r.checkFuncMisuse() {
bodyFunc.Body.List = append(bodyFunc.Body.List, r.assertNotExited(start, loop))
}
// Original loop body (already rewritten by editStmt during inspect).
bodyFunc.Body.List = append(bodyFunc.Body.List, body...)