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cmd/compile: use load and test instructions on s390x 

The load and test instructions compare the given value
against zero and will produce a condition code indicating
one of the following scenarios:

0: Result is zero
1: Result is less than zero
2: Result is greater than zero
3: Result is not a number (NaN)

The instruction can be used to simplify floating point comparisons
against zero, which can enable further optimizations.

This CL also reduces the size of .text section of math.test binary by around
0.7 KB (in hexadecimal, from 1358f0 to 135620).

Change-Id: I33cb714f0c6feebac7a1c46dfcc735e7daceff9c
Reviewed-on: https://go-review.googlesource.com/c/go/+/209159
Reviewed-by: Michael Munday <mike.munday@ibm.com>
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Ruixin(Peter) Bao 2019-11-26 15:33:37 -05:00 committed by Michael Munday
parent 6b6414cab4
commit 16cfab8d89
6 changed files with 129 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/cmd/compile/internal/s390x/ssa.go
View File

@ -605,6 +605,8 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
p.From.Reg = v.Args[0].Reg()
p.To.Type = obj.TYPE_REG
p.To.Reg = v.Reg()
case ssa.OpS390XLTDBR, ssa.OpS390XLTEBR:
opregreg(s, v.Op.Asm(), v.Args[0].Reg(), v.Args[0].Reg())
case ssa.OpS390XInvertFlags:
v.Fatalf("InvertFlags should never make it to codegen %v", v.LongString())
case ssa.OpS390XFlagEQ, ssa.OpS390XFlagLT, ssa.OpS390XFlagGT, ssa.OpS390XFlagOV:

6
src/cmd/compile/internal/ssa/gen/S390X.rules
View File

@ -1220,6 +1220,12 @@
(FSUB (FMUL y z) x) -> (FMSUB x y z)
(FSUBS (FMULS y z) x) -> (FMSUBS x y z)
// Convert floating point comparisons against zero into 'load and test' instructions.
(FCMP x (FMOVDconst [c])) && auxTo64F(c) == 0 -> (LTDBR x)
(FCMPS x (FMOVSconst [c])) && auxTo32F(c) == 0 -> (LTEBR x)
(FCMP (FMOVDconst [c]) x) && auxTo64F(c) == 0 -> (InvertFlags (LTDBR <v.Type> x))
(FCMPS (FMOVSconst [c]) x) && auxTo32F(c) == 0 -> (InvertFlags (LTEBR <v.Type> x))
// Fold memory operations into operations.
// Exclude global data (SB) because these instructions cannot handle relative addresses.
// TODO(mundaym): use LARL in the assembler to handle SB?

7
src/cmd/compile/internal/ssa/gen/S390XOps.go
View File

@ -181,6 +181,7 @@ func init() {
fpgp = regInfo{inputs: fponly, outputs: gponly}
gpfp = regInfo{inputs: gponly, outputs: fponly}
fp11 = regInfo{inputs: fponly, outputs: fponly}
fp1flags = regInfo{inputs: []regMask{fp}}
fp11clobber = regInfo{inputs: fponly, outputs: fponly}
fp2flags = regInfo{inputs: []regMask{fp, fp}}
@ -324,8 +325,10 @@ func init() {
{name: "CMPUconst", argLength: 1, reg: gp1flags, asm: "CMPU", typ: "Flags", aux: "Int32"}, // arg0 compare to auxint
{name: "CMPWUconst", argLength: 1, reg: gp1flags, asm: "CMPWU", typ: "Flags", aux: "Int32"}, // arg0 compare to auxint
{name: "FCMPS", argLength: 2, reg: fp2flags, asm: "CEBR", typ: "Flags"}, // arg0 compare to arg1, f32
{name: "FCMP", argLength: 2, reg: fp2flags, asm: "FCMPU", typ: "Flags"}, // arg0 compare to arg1, f64
{name: "FCMPS", argLength: 2, reg: fp2flags, asm: "CEBR", typ: "Flags"}, // arg0 compare to arg1, f32
{name: "FCMP", argLength: 2, reg: fp2flags, asm: "FCMPU", typ: "Flags"}, // arg0 compare to arg1, f64
{name: "LTDBR", argLength: 1, reg: fp1flags, asm: "LTDBR", typ: "Flags"}, // arg0 compare to 0, f64
{name: "LTEBR", argLength: 1, reg: fp1flags, asm: "LTEBR", typ: "Flags"}, // arg0 compare to 0, f32
{name: "SLD", argLength: 2, reg: sh21, asm: "SLD"}, // arg0 << arg1, shift amount is mod 64
{name: "SLW", argLength: 2, reg: sh21, asm: "SLW"}, // arg0 << arg1, shift amount is mod 32

22
src/cmd/compile/internal/ssa/opGen.go
View File

@ -2094,6 +2094,8 @@ const (
OpS390XCMPWUconst
OpS390XFCMPS
OpS390XFCMP
OpS390XLTDBR
OpS390XLTEBR
OpS390XSLD
OpS390XSLW
OpS390XSLDconst
@ -27998,6 +28000,26 @@ var opcodeTable = [...]opInfo{
},
},
},
{
name: "LTDBR",
argLen: 1,
asm: s390x.ALTDBR,
reg: regInfo{
inputs: []inputInfo{
{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
},
},
},
{
name: "LTEBR",
argLen: 1,
asm: s390x.ALTEBR,
reg: regInfo{
inputs: []inputInfo{
{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
},
},
},
{
name: "SLD",
argLen: 2,

84
src/cmd/compile/internal/ssa/rewriteS390X.go
View File

@ -612,6 +612,10 @@ func rewriteValueS390X(v *Value) bool {
return rewriteValueS390X_OpS390XFADD(v)
case OpS390XFADDS:
return rewriteValueS390X_OpS390XFADDS(v)
case OpS390XFCMP:
return rewriteValueS390X_OpS390XFCMP(v)
case OpS390XFCMPS:
return rewriteValueS390X_OpS390XFCMPS(v)
case OpS390XFMOVDload:
return rewriteValueS390X_OpS390XFMOVDload(v)
case OpS390XFMOVDloadidx:
@ -7230,6 +7234,86 @@ func rewriteValueS390X_OpS390XFADDS(v *Value) bool {
}
return false
}
func rewriteValueS390X_OpS390XFCMP(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
// match: (FCMP x (FMOVDconst [c]))
// cond: auxTo64F(c) == 0
// result: (LTDBR x)
for {
x := v_0
if v_1.Op != OpS390XFMOVDconst {
break
}
c := v_1.AuxInt
if !(auxTo64F(c) == 0) {
break
}
v.reset(OpS390XLTDBR)
v.AddArg(x)
return true
}
// match: (FCMP (FMOVDconst [c]) x)
// cond: auxTo64F(c) == 0
// result: (InvertFlags (LTDBR <v.Type> x))
for {
if v_0.Op != OpS390XFMOVDconst {
break
}
c := v_0.AuxInt
x := v_1
if !(auxTo64F(c) == 0) {
break
}
v.reset(OpS390XInvertFlags)
v0 := b.NewValue0(v.Pos, OpS390XLTDBR, v.Type)
v0.AddArg(x)
v.AddArg(v0)
return true
}
return false
}
func rewriteValueS390X_OpS390XFCMPS(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
// match: (FCMPS x (FMOVSconst [c]))
// cond: auxTo32F(c) == 0
// result: (LTEBR x)
for {
x := v_0
if v_1.Op != OpS390XFMOVSconst {
break
}
c := v_1.AuxInt
if !(auxTo32F(c) == 0) {
break
}
v.reset(OpS390XLTEBR)
v.AddArg(x)
return true
}
// match: (FCMPS (FMOVSconst [c]) x)
// cond: auxTo32F(c) == 0
// result: (InvertFlags (LTEBR <v.Type> x))
for {
if v_0.Op != OpS390XFMOVSconst {
break
}
c := v_0.AuxInt
x := v_1
if !(auxTo32F(c) == 0) {
break
}
v.reset(OpS390XInvertFlags)
v0 := b.NewValue0(v.Pos, OpS390XLTEBR, v.Type)
v0.AddArg(x)
v.AddArg(v0)
return true
}
return false
}
func rewriteValueS390X_OpS390XFMOVDload(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]

10
test/codegen/floats.go
View File

@ -122,6 +122,16 @@ func Cmp(f float64) bool {
return f > 4 || f < -4
}
func CmpZero64(f float64) bool {
// s390x:"LTDBR",-"FCMPU"
return f <= 0
}
func CmpZero32(f float32) bool {
// s390x:"LTEBR",-"CEBR"
return f <= 0
}
// ---------------- //
// Non-floats //
// ---------------- //