A similar change was made in 6g recently.

LEALs in cmd/go: 31440 before, 27867 after.

benchmark                 old ns/op    new ns/op    delta
BenchmarkBinaryTree17    7065794000   6723617000   -4.84%
BenchmarkFannkuch11      7767395000   7477945000   -3.73%
BenchmarkGobDecode         34708140     34857820   +0.43%
BenchmarkGobEncode         10998780     10960060   -0.35%
BenchmarkGzip            1603630000   1471052000   -8.27%
BenchmarkGunzip           242573900    240650400   -0.79%
BenchmarkJSONEncode       120842200    117966100   -2.38%
BenchmarkJSONDecode       247254900    249103100   +0.75%
BenchmarkMandelbrot200     29237330     29241790   +0.02%
BenchmarkParse              8111320      8096865   -0.18%
BenchmarkRevcomp         2595780000   2694153000   +3.79%
BenchmarkTemplate         276679600    264497000   -4.40%

benchmark                              old ns/op    new ns/op    delta
BenchmarkAppendFloatDecimal                  429          416   -3.03%
BenchmarkAppendFloat                         780          740   -5.13%
BenchmarkAppendFloatExp                      746          700   -6.17%
BenchmarkAppendFloatNegExp                   752          694   -7.71%
BenchmarkAppendFloatBig                     1228         1108   -9.77%
BenchmarkAppendFloat32Integer                457          416   -8.97%
BenchmarkAppendFloat32ExactFraction          662          631   -4.68%
BenchmarkAppendFloat32Point                  771          735   -4.67%
BenchmarkAppendFloat32Exp                    722          672   -6.93%
BenchmarkAppendFloat32NegExp                 724          659   -8.98%
BenchmarkAppendFloat64Fixed1                 429          400   -6.76%
BenchmarkAppendFloat64Fixed2                 463          442   -4.54%

Update #1914.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://golang.org/cl/6574043