| commit | c8e7c53b40023c92c9d7fa6beb1ca4223bd461ae | [log] [tgz] |
|---|---|---|
| author | David Chase <drchase@google.com> | Mon Sep 30 15:16:54 2019 -0400 |
| committer | David Chase <drchase@google.com> | Fri Oct 04 17:09:10 2019 +0000 |
| tree | ab8d11a83e72d494297adb17910e6138ee2b6bbf | |
| parent | 33ab6ccba066d94f8b8f9f502fddf04df90ea8cd [diff] |
cmd/compile: preserve statement mark in rematerialized values Statement markers on rematerializable values were getting lost in register allocation. This checks for that case (rematerializable input and using value share line number, but mark is on the input) and preserves the mark. When combined with other CLs in this series, this CL reduces the "nostmt" count (a line appears in the assembly, but no statement marker) for cmd/go from 413 to 277. The rematerialized input is usually a LEAQ (on AMD64). The cause is "complicated"; for example, a NilCheck originally has the statement mark (a good thing, if the NilCheck remains) but the NilCheck is removed and the mark floats to a Block end, then to a SliceMake. The SliceMake decomposes and goes dead without preserving its marker (its component values are elided in other rewrites and may target inputs with different line numbers), but before deadcode removes it from the graph it moves the mark to an input, which at that time happens to be a LocalAddr. This eventually transforms to a LEAQ. Change-Id: Iff91fc2a934357fb59ec46ac87b4a9b1057d9160 Reviewed-on: https://go-review.googlesource.com/c/go/+/198480 Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Jeremy Faller <jeremy@golang.org>
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