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cmd/internal/obj/ppc64: on Power10, use xxspltidp for float constants

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Any normal float32 constant can be generated by this instruction;
use xxspltidp when possible. This prefixed instruction is much
faster than the two instruction load sequence from the
float32/float64 constant pool.

Change-Id: Id751d9ffdae71463adbde66427b986f0b2ef74c2
Reviewed-on: https://go-review.googlesource.com/c/go/+/575555
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Paul Murphy <murp@ibm.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
This commit is contained in:
Paul E. Murphy 2024-03-29 16:11:36 -05:00 committed by Paul Murphy
parent 0f10ffec13
commit ebf7747dbe
3 changed files with 60 additions and 3 deletions
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28
src/cmd/internal/obj/ppc64/obj9.go
View file

@ -37,6 +37,7 @@ import (
"internal/abi"
"internal/buildcfg"
"log"
"math"
"math/bits"
"strings"
)
@ -90,6 +91,29 @@ func isNOTOCfunc(name string) bool {
}
}
// Try converting FMOVD/FMOVS to XXSPLTIDP. If it is converted,
// return true.
func convertFMOVtoXXSPLTIDP(p *obj.Prog) bool {
if p.From.Type != obj.TYPE_FCONST || buildcfg.GOPPC64 < 10 {
return false
}
v := p.From.Val.(float64)
if float64(float32(v)) != v {
return false
}
// Secondly, is this value a normal value?
ival := int64(math.Float32bits(float32(v)))
isDenorm := ival&0x7F800000 == 0 && ival&0x007FFFFF != 0
if !isDenorm {
p.As = AXXSPLTIDP
p.From.Type = obj.TYPE_CONST
p.From.Offset = ival
// Convert REG_Fx into equivalent REG_VSx
p.To.Reg = REG_VS0 + (p.To.Reg & 31)
}
return !isDenorm
}
func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
p.From.Class = 0
p.To.Class = 0
@ -111,7 +135,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
// Rewrite float constants to values stored in memory.
switch p.As {
case AFMOVS:
if p.From.Type == obj.TYPE_FCONST {
if p.From.Type == obj.TYPE_FCONST && !convertFMOVtoXXSPLTIDP(p) {
f32 := float32(p.From.Val.(float64))
p.From.Type = obj.TYPE_MEM
p.From.Sym = ctxt.Float32Sym(f32)
@ -123,7 +147,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
if p.From.Type == obj.TYPE_FCONST {
f64 := p.From.Val.(float64)
// Constant not needed in memory for float +/- 0
if f64 != 0 {
if f64 != 0 && !convertFMOVtoXXSPLTIDP(p) {
p.From.Type = obj.TYPE_MEM
p.From.Sym = ctxt.Float64Sym(f64)
p.From.Name = obj.NAME_EXTERN

31
test/codegen/floats.go
View file

@ -196,3 +196,34 @@ func Float32Max(a, b float32) float32 {
// ppc64/power10:"XSMAXJDP"
return max(a, b)
}
// ------------------------ //
// Constant Optimizations //
// ------------------------ //
func Float32Constant() float32 {
// ppc64x/power8:"FMOVS\t[$]f32\\.42440000\\(SB\\)"
// ppc64x/power9:"FMOVS\t[$]f32\\.42440000\\(SB\\)"
// ppc64x/power10:"XXSPLTIDP\t[$]1111752704,"
return 49.0
}
func Float64Constant() float64 {
// ppc64x/power8:"FMOVD\t[$]f64\\.4048800000000000\\(SB\\)"
// ppc64x/power9:"FMOVD\t[$]f64\\.4048800000000000\\(SB\\)"
// ppc64x/power10:"XXSPLTIDP\t[$]1111752704,"
return 49.0
}
func Float32DenormalConstant() float32 {
// ppc64x:"FMOVS\t[$]f32\\.00400000\\(SB\\)"
return 0x1p-127
}
// A float64 constant which can be exactly represented as a
// denormal float32 value. On ppc64x, denormal values cannot
// be used with XXSPLTIDP.
func Float64DenormalFloat32Constant() float64 {
// ppc64x:"FMOVD\t[$]f64\\.3800000000000000\\(SB\\)"
return 0x1p-127
}

4
test/codegen/math.go
View file

@ -204,7 +204,9 @@ func constantCheck32() bool {
func constantConvert32(x float32) float32 {
// amd64:"MOVSS\t[$]f32.3f800000\\(SB\\)"
// s390x:"FMOVS\t[$]f32.3f800000\\(SB\\)"
// ppc64x:"FMOVS\t[$]f32.3f800000\\(SB\\)"
// ppc64x/power8:"FMOVS\t[$]f32.3f800000\\(SB\\)"
// ppc64x/power9:"FMOVS\t[$]f32.3f800000\\(SB\\)"
// ppc64x/power10:"XXSPLTIDP\t[$]1065353216, VS0"
// arm64:"FMOVS\t[$]\\(1.0\\)"
if x > math.Float32frombits(0x3f800000) {
return -x