cmd/compile: add s390x intrinsics for Ceil, Floor, Round and Trunc
Ceil, Floor and Trunc are pre-existing intrinsics. Round is a new
function and has been added as an intrinsic in this CL. All of the
functions can be implemented as a single 'LOAD FP INTEGER'
instruction, FIDBR, on s390x.
name old time/op new time/op delta
Ceil 2.34ns ± 0% 0.85ns ± 0% -63.74% (p=0.000 n=5+4)
Floor 2.33ns ± 0% 0.85ns ± 1% -63.35% (p=0.008 n=5+5)
Round 4.23ns ± 0% 0.85ns ± 0% -79.89% (p=0.000 n=5+4)
Trunc 2.35ns ± 0% 0.85ns ± 0% -63.83% (p=0.029 n=4+4)
Change-Id: Idee7ba24a2899d12bf9afee4eedd6b4aaad3c510
Reviewed-on: https://go-review.googlesource.com/63890
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/cmd/compile/internal/ssa/gen/genericOps.go b/src/cmd/compile/internal/ssa/gen/genericOps.go
index 6f8d10a..2967d29 100644
--- a/src/cmd/compile/internal/ssa/gen/genericOps.go
+++ b/src/cmd/compile/internal/ssa/gen/genericOps.go
@@ -255,10 +255,23 @@
{name: "PopCount32", argLength: 1}, // Count bits in arg[0]
{name: "PopCount64", argLength: 1}, // Count bits in arg[0]
- {name: "Sqrt", argLength: 1}, // sqrt(arg0), float64 only
- {name: "Floor", argLength: 1}, // floor(arg0), float64 only
- {name: "Ceil", argLength: 1}, // ceil(arg0), float64 only
- {name: "Trunc", argLength: 1}, // trunc(arg0), float64 only
+ // Square root, float64 only.
+ // Special cases:
+ // +∞ → +∞
+ // ±0 → ±0 (sign preserved)
+ // x<0 → NaN
+ // NaN → NaN
+ {name: "Sqrt", argLength: 1}, // √arg0
+
+ // Round to integer, float64 only.
+ // Special cases:
+ // ±∞ → ±∞ (sign preserved)
+ // ±0 → ±0 (sign preserved)
+ // NaN → NaN
+ {name: "Floor", argLength: 1}, // round arg0 toward -∞
+ {name: "Ceil", argLength: 1}, // round arg0 toward +∞
+ {name: "Trunc", argLength: 1}, // round arg0 toward 0
+ {name: "Round", argLength: 1}, // round arg0 to nearest, ties away from 0
// Data movement, max argument length for Phi is indefinite so just pick
// a really large number
