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cmd/compile: eliminate dead code

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During walkexpr, we were assessing whether shifts were bounded.
However, that information was dropped on the floor during SSA conversion.
The SSA backend already finds all bounded shifts that walkexpr could have,
and at negligible extra cost (0.02% in alloc, CPU undetectable).

Change-Id: Ieda1af1a2a3ec99bfdc2b0b704c9b80ce8a34486
Reviewed-on: https://go-review.googlesource.com/c/148897
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2018-11-09 11:45:04 -08:00
parent 4ae49b5921
commit 78c0e1f81d
1 changed files with 1 additions and 10 deletions
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11
src/cmd/compile/internal/gc/walk.go
View file

@ -486,7 +486,7 @@ opswitch:
OIND, OSPTR, OITAB, OIDATA, OADDR:
n.Left = walkexpr(n.Left, init)
case OEFACE, OAND, OSUB, OMUL, OADD, OOR, OXOR:
case OEFACE, OAND, OSUB, OMUL, OADD, OOR, OXOR, OLSH, ORSH:
n.Left = walkexpr(n.Left, init)
n.Right = walkexpr(n.Right, init)
@ -538,15 +538,6 @@ opswitch:
n.SetTypecheck(1)
}
case OLSH, ORSH:
n.Left = walkexpr(n.Left, init)
n.Right = walkexpr(n.Right, init)
t := n.Left.Type
n.SetBounded(bounded(n.Right, 8*t.Width))
if Debug['m'] != 0 && n.Bounded() && !Isconst(n.Right, CTINT) {
Warn("shift bounds check elided")
}
case OCOMPLEX:
// Use results from call expression as arguments for complex.
if n.Left == nil && n.Right == nil {