From a34fddf46c47a86e7a7cab32be858f7e8d0feb70 Mon Sep 17 00:00:00 2001 From: Philip Hofer Date: Mon, 14 Nov 2016 17:05:46 -0800 Subject: [PATCH] cmd/compile: in cse, allow for new ssa values The table of rewrites in ssa/cse is not sized appropriately for ssa IDs that are created during copying of selects into new blocks. Fixes #17918 Change-Id: I65fe86c6aab5efa679aa473aadc4ee6ea882cd41 Reviewed-on: https://go-review.googlesource.com/33240 Reviewed-by: Cherry Zhang Reviewed-by: David Chase Run-TryBot: Cherry Zhang TryBot-Result: Gobot Gobot --- src/cmd/compile/internal/ssa/cse.go | 5 +++- test/fixedbugs/issue17918.go | 41 +++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+), 1 deletion(-) create mode 100644 test/fixedbugs/issue17918.go diff --git a/src/cmd/compile/internal/ssa/cse.go b/src/cmd/compile/internal/ssa/cse.go index 9410433325..4e07c89b88 100644 --- a/src/cmd/compile/internal/ssa/cse.go +++ b/src/cmd/compile/internal/ssa/cse.go @@ -188,7 +188,10 @@ func cse(f *Func) { for _, b := range f.Blocks { out: for _, v := range b.Values { - if rewrite[v.ID] != nil { + // New values are created when selectors are copied to + // a new block. We can safely ignore those new values, + // since they have already been copied (issue 17918). + if int(v.ID) >= len(rewrite) || rewrite[v.ID] != nil { continue } if v.Op != OpSelect0 && v.Op != OpSelect1 { diff --git a/test/fixedbugs/issue17918.go b/test/fixedbugs/issue17918.go new file mode 100644 index 0000000000..88ede6f7b7 --- /dev/null +++ b/test/fixedbugs/issue17918.go @@ -0,0 +1,41 @@ +// compile + +// Copyright 2016 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 17918: slice out-of-bounds in ssa/cse + +package dead + +import ( + "fmt" + "time" +) + +var ( + units = []struct { + divisor time.Duration + unit rune + }{ + {1000000, 's'}, + {60, 'm'}, + {60, 'h'}, + {24, 'd'}, + {7, 'w'}, + } +) + +func foobar(d time.Duration) string { + d /= time.Microsecond + unit := 'u' + + for _, f := range units { + if d%f.divisor != 0 { + break + } + d /= f.divisor + unit = f.unit + } + return fmt.Sprintf("%d%c", d, unit) +} -- 2.50.0