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cmd/compile: fix FMA negative commutativity of riscv64

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According to RISCV manual 11.6:

FMADD x,y,z computes x*y+z and
FNMADD x,y,z => -x*y-z
FMSUB x,y,z => x*y-z
FNMSUB x,y,z => -x*y+z respectively

However our implement of SSA convert FMADD -x,y,z to FNMADD x,y,z which
is wrong and should be convert to FNMSUB according to manual.

Change-Id: Ib297bc83824e121fd7dda171ed56ea9694a4e575
Reviewed-on: https://go-review.googlesource.com/c/go/+/506575
Run-TryBot: M Zhuo <mzh@golangcn.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Joedian Reid <joedian@golang.org>
Reviewed-by: Michael Munday <mike.munday@lowrisc.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Meng Zhuo 2023-06-27 23:22:04 +08:00 committed by Keith Randall
parent c8dad424bf
commit 3fce111535
3 changed files with 17 additions and 17 deletions
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10
src/cmd/compile/internal/ssa/_gen/RISCV64.rules
View file

@ -836,11 +836,11 @@
//
// Key:
//
// [+ -](x * y) [+ -] z.
// _ N A S
// D U
// D B
// [+ -](x * y [+ -] z).
// _ N A S
// D U
// D B
//
// Note: multiplication commutativity handled by rule generator.
(F(MADD|NMADD|MSUB|NMSUB)D neg:(FNEGD x) y z) && neg.Uses == 1 => (F(NMADD|MADD|NMSUB|MSUB)D x y z)
(F(MADD|NMADD|MSUB|NMSUB)D neg:(FNEGD x) y z) && neg.Uses == 1 => (F(NMSUB|MSUB|NMADD|MADD)D x y z)
(F(MADD|NMADD|MSUB|NMSUB)D x y neg:(FNEGD z)) && neg.Uses == 1 => (F(MSUB|NMSUB|MADD|NMADD)D x y z)

16
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View file

@ -3322,7 +3322,7 @@ func rewriteValueRISCV64_OpRISCV64FMADDD(v *Value) bool {
v_0 := v.Args[0]
// match: (FMADDD neg:(FNEGD x) y z)
// cond: neg.Uses == 1
// result: (FNMADDD x y z)
// result: (FNMSUBD x y z)
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
neg := v_0
@ -3335,7 +3335,7 @@ func rewriteValueRISCV64_OpRISCV64FMADDD(v *Value) bool {
if !(neg.Uses == 1) {
continue
}
v.reset(OpRISCV64FNMADDD)
v.reset(OpRISCV64FNMSUBD)
v.AddArg3(x, y, z)
return true
}
@ -3367,7 +3367,7 @@ func rewriteValueRISCV64_OpRISCV64FMSUBD(v *Value) bool {
v_0 := v.Args[0]
// match: (FMSUBD neg:(FNEGD x) y z)
// cond: neg.Uses == 1
// result: (FNMSUBD x y z)
// result: (FNMADDD x y z)
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
neg := v_0
@ -3380,7 +3380,7 @@ func rewriteValueRISCV64_OpRISCV64FMSUBD(v *Value) bool {
if !(neg.Uses == 1) {
continue
}
v.reset(OpRISCV64FNMSUBD)
v.reset(OpRISCV64FNMADDD)
v.AddArg3(x, y, z)
return true
}
@ -3412,7 +3412,7 @@ func rewriteValueRISCV64_OpRISCV64FNMADDD(v *Value) bool {
v_0 := v.Args[0]
// match: (FNMADDD neg:(FNEGD x) y z)
// cond: neg.Uses == 1
// result: (FMADDD x y z)
// result: (FMSUBD x y z)
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
neg := v_0
@ -3425,7 +3425,7 @@ func rewriteValueRISCV64_OpRISCV64FNMADDD(v *Value) bool {
if !(neg.Uses == 1) {
continue
}
v.reset(OpRISCV64FMADDD)
v.reset(OpRISCV64FMSUBD)
v.AddArg3(x, y, z)
return true
}
@ -3457,7 +3457,7 @@ func rewriteValueRISCV64_OpRISCV64FNMSUBD(v *Value) bool {
v_0 := v.Args[0]
// match: (FNMSUBD neg:(FNEGD x) y z)
// cond: neg.Uses == 1
// result: (FMSUBD x y z)
// result: (FMADDD x y z)
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
neg := v_0
@ -3470,7 +3470,7 @@ func rewriteValueRISCV64_OpRISCV64FNMSUBD(v *Value) bool {
if !(neg.Uses == 1) {
continue
}
v.reset(OpRISCV64FMSUBD)
v.reset(OpRISCV64FMADDD)
v.AddArg3(x, y, z)
return true
}

8
test/codegen/math.go
View file

@ -143,13 +143,13 @@ func fms(x, y, z float64) float64 {
return math.FMA(x, y, -z)
}
func fnma(x, y, z float64) float64 {
// riscv64:"FNMADDD"
func fnms(x, y, z float64) float64 {
// riscv64:"FNMSUBD",-"FNMADDD"
return math.FMA(-x, y, z)
}
func fnms(x, y, z float64) float64 {
// riscv64:"FNMSUBD"
func fnma(x, y, z float64) float64 {
// riscv64:"FNMADDD",-"FNMSUBD"
return math.FMA(x, -y, -z)
}