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cmd/compile: simplify OpSlicemask optimization

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The previous CL introduced isConstDelta. Use it to simplify the
OpSlicemask optimization in the prove pass. This passes toolstash
-cmp.

Change-Id: If2aa762db4cdc0cd1c581a536340530a9831081b
Reviewed-on: https://go-review.googlesource.com/87481
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Austin Clements 2018-01-11 16:50:09 -05:00
parent 6436270dad
commit da022da900
1 changed files with 3 additions and 14 deletions
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17
src/cmd/compile/internal/ssa/prove.go
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@ -748,19 +748,8 @@ func simplifyBlock(sdom SparseTree, ft *factsTable, b *Block) {
if v.Op != OpSlicemask {
continue
}
add := v.Args[0]
if add.Op != OpAdd64 && add.Op != OpAdd32 {
continue
}
// Note that the arg of slicemask was originally a sub, but
// was rewritten to an add by generic.rules (if the thing
// being subtracted was a constant).
x := add.Args[0]
y := add.Args[1]
if x.Op == OpConst64 || x.Op == OpConst32 {
x, y = y, x
}
if y.Op != OpConst64 && y.Op != OpConst32 {
x, delta := isConstDelta(v.Args[0])
if x == nil {
continue
}
// slicemask(x + y)
@ -769,7 +758,7 @@ func simplifyBlock(sdom SparseTree, ft *factsTable, b *Block) {
if !ok {
continue
}
if lim.umin > uint64(-y.AuxInt) {
if lim.umin > uint64(-delta) {
if v.Args[0].Op == OpAdd64 {
v.reset(OpConst64)
} else {