cmd/compile: allow floating point Ops to produce flags on s390x

On s390x, some floating point arithmetic instructions (FSUB, FADD)  generate flag.
This patch allows those related SSA ops to return a tuple, where the second argument of
the tuple is the generated flag. We can use the flag and remove the
subsequent comparison instruction (e.g: LTDBR).

This CL also reduces the .text section for math.test binary by 0.4KB.

Benchmarks:
name                    old time/op  new time/op  delta
Acos-18                 12.1ns ± 0%  12.1ns ± 0%     ~     (all equal)
Acosh-18                18.5ns ± 0%  18.5ns ± 0%     ~     (all equal)
Asin-18                 13.1ns ± 0%  13.1ns ± 0%     ~     (all equal)
Asinh-18                19.4ns ± 0%  19.5ns ± 1%     ~     (p=0.444 n=5+5)
Atan-18                 10.0ns ± 0%  10.0ns ± 0%     ~     (all equal)
Atanh-18                19.1ns ± 1%  19.2ns ± 2%     ~     (p=0.841 n=5+5)
Atan2-18                16.4ns ± 0%  16.4ns ± 0%     ~     (all equal)
Cbrt-18                 14.8ns ± 0%  14.8ns ± 0%     ~     (all equal)
Ceil-18                 0.78ns ± 0%  0.78ns ± 0%     ~     (all equal)
Copysign-18             0.80ns ± 0%  0.80ns ± 0%     ~     (all equal)
Cos-18                  7.19ns ± 0%  7.19ns ± 0%     ~     (p=0.556 n=4+5)
Cosh-18                 12.4ns ± 0%  12.4ns ± 0%     ~     (all equal)
Erf-18                  10.8ns ± 0%  10.8ns ± 0%     ~     (all equal)
Erfc-18                 11.0ns ± 0%  11.0ns ± 0%     ~     (all equal)
Erfinv-18               23.0ns ±16%  26.8ns ± 1%  +16.90%  (p=0.008 n=5+5)
Erfcinv-18              23.3ns ±15%  26.1ns ± 7%     ~     (p=0.087 n=5+5)
Exp-18                  8.67ns ± 0%  8.67ns ± 0%     ~     (p=1.000 n=4+4)
ExpGo-18                50.8ns ± 3%  52.4ns ± 2%     ~     (p=0.063 n=5+5)
Expm1-18                9.49ns ± 1%  9.47ns ± 0%     ~     (p=1.000 n=5+5)
Exp2-18                 52.7ns ± 1%  50.5ns ± 3%   -4.10%  (p=0.024 n=5+5)
Exp2Go-18               50.6ns ± 1%  48.4ns ± 3%   -4.39%  (p=0.008 n=5+5)
Abs-18                  0.67ns ± 0%  0.67ns ± 0%     ~     (p=0.444 n=5+5)
Dim-18                  1.02ns ± 0%  1.03ns ± 0%   +0.98%  (p=0.008 n=5+5)
Floor-18                0.78ns ± 0%  0.78ns ± 0%     ~     (all equal)
Max-18                  3.09ns ± 1%  3.05ns ± 0%   -1.42%  (p=0.008 n=5+5)
Min-18                  3.32ns ± 1%  3.30ns ± 0%   -0.72%  (p=0.016 n=5+4)
Mod-18                  62.3ns ± 1%  65.8ns ± 3%   +5.55%  (p=0.008 n=5+5)
Frexp-18                5.05ns ± 2%  4.98ns ± 0%     ~     (p=0.683 n=5+5)
Gamma-18                24.4ns ± 0%  24.1ns ± 0%   -1.23%  (p=0.008 n=5+5)
Hypot-18                10.3ns ± 0%  10.3ns ± 0%     ~     (all equal)
HypotGo-18              10.2ns ± 0%  10.2ns ± 0%     ~     (all equal)
Ilogb-18                3.56ns ± 1%  3.54ns ± 0%     ~     (p=0.595 n=5+5)
J0-18                    113ns ± 0%   108ns ± 1%   -4.42%  (p=0.016 n=4+5)
J1-18                    115ns ± 0%   109ns ± 1%   -4.87%  (p=0.016 n=4+5)
Jn-18                    240ns ± 0%   230ns ± 2%   -4.41%  (p=0.008 n=5+5)
Ldexp-18                6.19ns ± 0%  6.19ns ± 0%     ~     (p=0.444 n=5+5)
Lgamma-18               32.2ns ± 0%  32.2ns ± 0%     ~     (all equal)
Log-18                  13.1ns ± 0%  13.1ns ± 0%     ~     (all equal)
Logb-18                 4.23ns ± 0%  4.22ns ± 0%     ~     (p=0.444 n=5+5)
Log1p-18                12.7ns ± 0%  12.7ns ± 0%     ~     (all equal)
Log10-18                18.1ns ± 0%  18.2ns ± 0%     ~     (p=0.167 n=5+5)
Log2-18                 14.0ns ± 0%  14.0ns ± 0%     ~     (all equal)
Modf-18                 10.4ns ± 0%  10.5ns ± 0%   +0.96%  (p=0.016 n=4+5)
Nextafter32-18          11.3ns ± 0%  11.3ns ± 0%     ~     (all equal)
Nextafter64-18          4.01ns ± 1%  3.97ns ± 0%     ~     (p=0.333 n=5+4)
PowInt-18               32.7ns ± 0%  32.7ns ± 0%     ~     (all equal)
PowFrac-18              33.2ns ± 0%  33.1ns ± 0%     ~     (p=0.095 n=4+5)
Pow10Pos-18             1.58ns ± 0%  1.58ns ± 0%     ~     (all equal)
Pow10Neg-18             5.81ns ± 0%  5.81ns ± 0%     ~     (all equal)
Round-18                0.78ns ± 0%  0.78ns ± 0%     ~     (all equal)
RoundToEven-18          0.78ns ± 0%  0.78ns ± 0%     ~     (all equal)
Remainder-18            40.6ns ± 0%  40.7ns ± 0%     ~     (p=0.238 n=5+4)
Signbit-18              1.57ns ± 0%  1.57ns ± 0%     ~     (all equal)
Sin-18                  6.75ns ± 0%  6.74ns ± 0%     ~     (p=0.333 n=5+4)
Sincos-18               29.5ns ± 0%  29.5ns ± 0%     ~     (all equal)
Sinh-18                 14.4ns ± 0%  14.4ns ± 0%     ~     (all equal)
SqrtIndirect-18         3.97ns ± 0%  4.15ns ± 0%   +4.59%  (p=0.008 n=5+5)
SqrtLatency-18          8.01ns ± 0%  8.01ns ± 0%     ~     (all equal)
SqrtIndirectLatency-18  11.6ns ± 0%  11.6ns ± 0%     ~     (all equal)
SqrtGoLatency-18        44.7ns ± 0%  45.0ns ± 0%   +0.67%  (p=0.008 n=5+5)
SqrtPrime-18            1.26µs ± 0%  1.27µs ± 0%   +0.63%  (p=0.029 n=4+4)
Tan-18                  11.1ns ± 0%  11.1ns ± 0%     ~     (all equal)
Tanh-18                 15.8ns ± 0%  15.8ns ± 0%     ~     (all equal)
Trunc-18                0.78ns ± 0%  0.78ns ± 0%     ~     (all equal)
Y0-18                    113ns ± 2%   108ns ± 3%   -5.11%  (p=0.008 n=5+5)
Y1-18                    112ns ± 3%   107ns ± 0%   -4.29%  (p=0.000 n=5+4)
Yn-18                    229ns ± 0%   220ns ± 1%   -3.76%  (p=0.016 n=4+5)
Float64bits-18          1.09ns ± 0%  1.09ns ± 0%     ~     (all equal)
Float64frombits-18      0.55ns ± 0%  0.55ns ± 0%     ~     (all equal)
Float32bits-18          0.96ns ±16%  0.86ns ± 0%     ~     (p=0.563 n=5+5)
Float32frombits-18      1.03ns ±28%  0.84ns ± 0%     ~     (p=0.167 n=5+5)
FMA-18                  1.60ns ± 0%  1.60ns ± 0%     ~     (all equal)
[Geo mean]              10.0ns        9.9ns        -0.41%
Change-Id: Ief7e63ea5a8ba404b0a4696e12b9b7e0b05a9a03
Reviewed-on: https://go-review.googlesource.com/c/go/+/209160
Reviewed-by: Michael Munday <mike.munday@ibm.com>
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 0 insertions, 4 deletions

diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index ee5e1bd063..2168d262aa 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -26944,7 +26944,6 @@ var opcodeTable = [...]opInfo{
 		argLen:       2,
 		commutative:  true,
 		resultInArg0: true,
-		clobberFlags: true,
 		asm:          s390x.AFADDS,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -26961,7 +26960,6 @@ var opcodeTable = [...]opInfo{
 		argLen:       2,
 		commutative:  true,
 		resultInArg0: true,
-		clobberFlags: true,
 		asm:          s390x.AFADD,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -26977,7 +26975,6 @@ var opcodeTable = [...]opInfo{
 		name:         "FSUBS",
 		argLen:       2,
 		resultInArg0: true,
-		clobberFlags: true,
 		asm:          s390x.AFSUBS,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -26993,7 +26990,6 @@ var opcodeTable = [...]opInfo{
 		name:         "FSUB",
 		argLen:       2,
 		resultInArg0: true,
-		clobberFlags: true,
 		asm:          s390x.AFSUB,
 		reg: regInfo{
 			inputs: []inputInfo{