From 66ce8aa88d144338868b0d3ab8c895608a460750 Mon Sep 17 00:00:00 2001 From: Than McIntosh Date: Tue, 4 May 2021 16:18:56 -0400 Subject: [PATCH] cmd/compile: handle degenerate entry blocks in -N debug gen The code that created DWARF debug var locations for input parameters in the non-optimized case for regabi was not doing the right thing for degenerate functions with infinite loops. Detect these cases and don't try to emit the normal location data. Fixes #45948. Change-Id: I2717fc4bac2e03d5d850a6ec8a09ed05fed0c896 Reviewed-on: https://go-review.googlesource.com/c/go/+/316752 Trust: Than McIntosh Run-TryBot: Than McIntosh Reviewed-by: Cherry Zhang TryBot-Result: Go Bot --- src/cmd/compile/internal/ssa/debug.go | 12 +++++++++--- test/fixedbugs/issue45948.go | 16 ++++++++++++++++ 2 files changed, 25 insertions(+), 3 deletions(-) create mode 100644 test/fixedbugs/issue45948.go diff --git a/src/cmd/compile/internal/ssa/debug.go b/src/cmd/compile/internal/ssa/debug.go index ee522f41ef..2f379c9e2c 100644 --- a/src/cmd/compile/internal/ssa/debug.go +++ b/src/cmd/compile/internal/ssa/debug.go @@ -1362,9 +1362,6 @@ func BuildFuncDebugNoOptimized(ctxt *obj.Link, f *Func, loggingEnabled bool, sta // Locate the value corresponding to the last spill of // an input register. afterPrologVal := locatePrologEnd(f) - if afterPrologVal == ID(-1) { - panic(fmt.Sprintf("internal error: f=%s: can't locate after prolog value", f.Name)) - } // Walk the input params again and process the register-resident elements. pidx := 0 @@ -1381,6 +1378,15 @@ func BuildFuncDebugNoOptimized(ctxt *obj.Link, f *Func, loggingEnabled bool, sta slid := len(fd.VarSlots) fd.VarSlots = append(fd.VarSlots, []SlotID{SlotID(slid)}) + if afterPrologVal == ID(-1) { + // This can happen for degenerate functions with infinite + // loops such as that in issue 45948. In such cases, leave + // the var/slot set up for the param, but don't try to + // emit a location list. + pidx++ + continue + } + // Param is arriving in one or more registers. We need a 2-element // location expression for it. First entry in location list // will correspond to lifetime in input registers. diff --git a/test/fixedbugs/issue45948.go b/test/fixedbugs/issue45948.go new file mode 100644 index 0000000000..37f8e70e2b --- /dev/null +++ b/test/fixedbugs/issue45948.go @@ -0,0 +1,16 @@ +// compile -N + +// Copyright 2021 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Issue 45948: assert in debug generation for degenerate +// function with infinite loop. + +package p + +func f(p int) { +L: + goto L + +} -- 2.48.1