Commit 4cef0e98 authored by Josh Bleecher Snyder's avatar Josh Bleecher Snyder

cmd/compile: don't generate algs for [0]T and [1]T

All [0]T values are equal.
[1]T values are equal iff their sole components are.

This types show up most frequently as a by-product of variadic
function calls, such as fmt.Printf("abc") or fmt.Printf("%v", x).

Cuts 12k off cmd/go and 22k off golang.org/x/tools/cmd/godoc, approx 0.1% each.

For #6853 and #9930

Change-Id: Ic9b7aeb8cc945804246340f6f5e67bbf6008773e
Reviewed-on: https://go-review.googlesource.com/19766Reviewed-by: default avatarDavid Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
parent 9ad41f62
......@@ -465,6 +465,15 @@ func algtype1(t *Type, bad **Type) int {
return a
}
switch t.Bound {
case 0:
// We checked above that the element type is comparable.
return AMEM
case 1:
// Single-element array is same as its lone element.
return a
}
return -1 // needs special compare
case TSTRUCT:
......
......@@ -3193,6 +3193,21 @@ func walkcompare(np **Node, init **NodeList) {
return
}
if t.Etype == TARRAY {
// Zero- or single-element array, of any type.
switch t.Bound {
case 0:
finishcompare(np, n, Nodbool(n.Op == OEQ), init)
return
case 1:
l0 := Nod(OINDEX, l, Nodintconst(0))
r0 := Nod(OINDEX, r, Nodintconst(0))
a := Nod(n.Op, l0, r0)
finishcompare(np, n, a, init)
return
}
}
if t.Etype == TSTRUCT && countfield(t) <= 4 {
// Struct of four or fewer fields.
// Inline comparisons.
......
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