[go] cmd/compile/internal/ssa: simplify riscv64 FCLASSD rewrite rules
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Michael Munday (Gerrit)
Nov 3, 2025, 6:15:47 PM (2 days ago) Nov 3
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Michael Munday has uploaded the change for review![]( "Open in Gerrit")
Commit message
cmd/compile/internal/ssa: simplify riscv64 FCLASSD rewrite rules
We don't need to check that the bit patterns of the constants
match, it is sufficient to just check the constant is equal to the
given value.
While we're here also change the FCLASSD rules to use a bit pattern
for the mask. I think this improves readability, particularly as
more uses of FCLASSD get added (e.g. CL 717560).
These changes should not affect codegen.
Change-Id: I92a6338dc71e6a71e04306f67d7d86016c6e9c47
Change diff
diff --git a/src/cmd/compile/internal/ssa/_gen/RISCV64.rules b/src/cmd/compile/internal/ssa/_gen/RISCV64.rules
index 49bdbc8..31829a5 100644
--- a/src/cmd/compile/internal/ssa/_gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/_gen/RISCV64.rules
@@ -823,16 +823,16 @@
(F(MADD|NMADD|MSUB|NMSUB)D x y neg:(FNEGD z)) && neg.Uses == 1 => (F(MSUB|NMSUB|MADD|NMADD)D x y z)
// Test for -∞ (bit 0) using 64 bit classify instruction.
-(FLTD x (FMOVDconst [c])) && float64ExactBits(c, -math.MaxFloat64) => (ANDI [1] (FCLASSD x))
-(FLED (FMOVDconst [c]) x) && float64ExactBits(c, -math.MaxFloat64) => (SNEZ (ANDI <typ.Int64> [0xff &^ 1] (FCLASSD x)))
-(FEQD x (FMOVDconst [c])) && float64ExactBits(c, math.Inf(-1)) => (ANDI [1] (FCLASSD x))
-(FNED x (FMOVDconst [c])) && float64ExactBits(c, math.Inf(-1)) => (SEQZ (ANDI <typ.Int64> [1] (FCLASSD x)))
+(FLTD x (FMOVDconst [-math.MaxFloat64])) => (ANDI [0b00_0000_0001] (FCLASSD x))
+(FLED (FMOVDconst [-math.MaxFloat64]) x) => (SNEZ (ANDI <typ.Int64> [0b00_1111_1110] (FCLASSD x)))
+(FEQD x (FMOVDconst [math.Inf(-1)])) => (ANDI [0b00_0000_0001] (FCLASSD x))
+(FNED x (FMOVDconst [math.Inf(-1)])) => (SEQZ (ANDI <typ.Int64> [0b00_0000_0001] (FCLASSD x)))
// Test for +∞ (bit 7) using 64 bit classify instruction.
-(FLTD (FMOVDconst [c]) x) && float64ExactBits(c, math.MaxFloat64) => (SNEZ (ANDI <typ.Int64> [1<<7] (FCLASSD x)))
-(FLED x (FMOVDconst [c])) && float64ExactBits(c, math.MaxFloat64) => (SNEZ (ANDI <typ.Int64> [0xff &^ (1<<7)] (FCLASSD x)))
-(FEQD x (FMOVDconst [c])) && float64ExactBits(c, math.Inf(1)) => (SNEZ (ANDI <typ.Int64> [1<<7] (FCLASSD x)))
-(FNED x (FMOVDconst [c])) && float64ExactBits(c, math.Inf(1)) => (SEQZ (ANDI <typ.Int64> [1<<7] (FCLASSD x)))
+(FLTD (FMOVDconst [math.MaxFloat64]) x) => (SNEZ (ANDI <typ.Int64> [0b00_1000_0000] (FCLASSD x)))
+(FLED x (FMOVDconst [math.MaxFloat64])) => (SNEZ (ANDI <typ.Int64> [0b00_0111_1111] (FCLASSD x)))
+(FEQD x (FMOVDconst [math.Inf(1)])) => (SNEZ (ANDI <typ.Int64> [0b00_1000_0000] (FCLASSD x)))
+(FNED x (FMOVDconst [math.Inf(1)])) => (SEQZ (ANDI <typ.Int64> [0b00_1000_0000] (FCLASSD x)))
//
// Optimisations for rva22u64 and above.
diff --git a/src/cmd/compile/internal/ssa/rewrite.go b/src/cmd/compile/internal/ssa/rewrite.go
index a822ebc..0730897 100644
--- a/src/cmd/compile/internal/ssa/rewrite.go
+++ b/src/cmd/compile/internal/ssa/rewrite.go
@@ -765,10 +765,6 @@
return i
}
-func float64ExactBits(f float64, c float64) bool {
- return math.Float64bits(f) == math.Float64bits(c)
-}
-
func flagConstantToAuxInt(x flagConstant) int64 {
return int64(x)
}
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index 8a390eb..52870fe 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -3582,21 +3582,16 @@
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
- // match: (FEQD x (FMOVDconst [c]))
- // cond: float64ExactBits(c, math.Inf(-1))
- // result: (ANDI [1] (FCLASSD x))
+ // match: (FEQD x (FMOVDconst [math.Inf(-1)]))
+ // result: (ANDI [0b00_0000_0001] (FCLASSD x))
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
x := v_0
- if v_1.Op != OpRISCV64FMOVDconst {
- continue
- }
- c := auxIntToFloat64(v_1.AuxInt)
- if !(float64ExactBits(c, math.Inf(-1))) {
+ if v_1.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_1.AuxInt) != math.Inf(-1) {
continue
}
v.reset(OpRISCV64ANDI)
- v.AuxInt = int64ToAuxInt(1)
+ v.AuxInt = int64ToAuxInt(0b00_0000_0001)
v0 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v0.AddArg(x)
v.AddArg(v0)
@@ -3604,22 +3599,17 @@
}
break
}
- // match: (FEQD x (FMOVDconst [c]))
- // cond: float64ExactBits(c, math.Inf(1))
- // result: (SNEZ (ANDI <typ.Int64> [1<<7] (FCLASSD x)))
+ // match: (FEQD x (FMOVDconst [math.Inf(1)]))
+ // result: (SNEZ (ANDI <typ.Int64> [0b00_1000_0000] (FCLASSD x)))
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
x := v_0
- if v_1.Op != OpRISCV64FMOVDconst {
- continue
- }
- c := auxIntToFloat64(v_1.AuxInt)
- if !(float64ExactBits(c, math.Inf(1))) {
+ if v_1.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_1.AuxInt) != math.Inf(1) {
continue
}
v.reset(OpRISCV64SNEZ)
v0 := b.NewValue0(v.Pos, OpRISCV64ANDI, typ.Int64)
- v0.AuxInt = int64ToAuxInt(1 << 7)
+ v0.AuxInt = int64ToAuxInt(0b00_1000_0000)
v1 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v1.AddArg(x)
v0.AddArg(v1)
@@ -3635,42 +3625,32 @@
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
- // match: (FLED (FMOVDconst [c]) x)
- // cond: float64ExactBits(c, -math.MaxFloat64)
- // result: (SNEZ (ANDI <typ.Int64> [0xff &^ 1] (FCLASSD x)))
+ // match: (FLED (FMOVDconst [-math.MaxFloat64]) x)
+ // result: (SNEZ (ANDI <typ.Int64> [0b00_1111_1110] (FCLASSD x)))
for {
- if v_0.Op != OpRISCV64FMOVDconst {
+ if v_0.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_0.AuxInt) != -math.MaxFloat64 {
break
}
- c := auxIntToFloat64(v_0.AuxInt)
x := v_1
- if !(float64ExactBits(c, -math.MaxFloat64)) {
- break
- }
v.reset(OpRISCV64SNEZ)
v0 := b.NewValue0(v.Pos, OpRISCV64ANDI, typ.Int64)
- v0.AuxInt = int64ToAuxInt(0xff &^ 1)
+ v0.AuxInt = int64ToAuxInt(0b00_1111_1110)
v1 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v1.AddArg(x)
v0.AddArg(v1)
v.AddArg(v0)
return true
}
- // match: (FLED x (FMOVDconst [c]))
- // cond: float64ExactBits(c, math.MaxFloat64)
- // result: (SNEZ (ANDI <typ.Int64> [0xff &^ (1<<7)] (FCLASSD x)))
+ // match: (FLED x (FMOVDconst [math.MaxFloat64]))
+ // result: (SNEZ (ANDI <typ.Int64> [0b00_0111_1111] (FCLASSD x)))
for {
x := v_0
- if v_1.Op != OpRISCV64FMOVDconst {
- break
- }
- c := auxIntToFloat64(v_1.AuxInt)
- if !(float64ExactBits(c, math.MaxFloat64)) {
+ if v_1.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_1.AuxInt) != math.MaxFloat64 {
break
}
v.reset(OpRISCV64SNEZ)
v0 := b.NewValue0(v.Pos, OpRISCV64ANDI, typ.Int64)
- v0.AuxInt = int64ToAuxInt(0xff &^ (1 << 7))
+ v0.AuxInt = int64ToAuxInt(0b00_0111_1111)
v1 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v1.AddArg(x)
v0.AddArg(v1)
@@ -3684,40 +3664,30 @@
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
- // match: (FLTD x (FMOVDconst [c]))
- // cond: float64ExactBits(c, -math.MaxFloat64)
- // result: (ANDI [1] (FCLASSD x))
+ // match: (FLTD x (FMOVDconst [-math.MaxFloat64]))
+ // result: (ANDI [0b00_0000_0001] (FCLASSD x))
for {
x := v_0
- if v_1.Op != OpRISCV64FMOVDconst {
- break
- }
- c := auxIntToFloat64(v_1.AuxInt)
- if !(float64ExactBits(c, -math.MaxFloat64)) {
+ if v_1.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_1.AuxInt) != -math.MaxFloat64 {
break
}
v.reset(OpRISCV64ANDI)
- v.AuxInt = int64ToAuxInt(1)
+ v.AuxInt = int64ToAuxInt(0b00_0000_0001)
v0 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v0.AddArg(x)
v.AddArg(v0)
return true
}
- // match: (FLTD (FMOVDconst [c]) x)
- // cond: float64ExactBits(c, math.MaxFloat64)
- // result: (SNEZ (ANDI <typ.Int64> [1<<7] (FCLASSD x)))
+ // match: (FLTD (FMOVDconst [math.MaxFloat64]) x)
+ // result: (SNEZ (ANDI <typ.Int64> [0b00_1000_0000] (FCLASSD x)))
for {
- if v_0.Op != OpRISCV64FMOVDconst {
+ if v_0.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_0.AuxInt) != math.MaxFloat64 {
break
}
- c := auxIntToFloat64(v_0.AuxInt)
x := v_1
- if !(float64ExactBits(c, math.MaxFloat64)) {
- break
- }
v.reset(OpRISCV64SNEZ)
v0 := b.NewValue0(v.Pos, OpRISCV64ANDI, typ.Int64)
- v0.AuxInt = int64ToAuxInt(1 << 7)
+ v0.AuxInt = int64ToAuxInt(0b00_1000_0000)
v1 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v1.AddArg(x)
v0.AddArg(v1)
@@ -4155,22 +4125,17 @@
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
- // match: (FNED x (FMOVDconst [c]))
- // cond: float64ExactBits(c, math.Inf(-1))
- // result: (SEQZ (ANDI <typ.Int64> [1] (FCLASSD x)))
+ // match: (FNED x (FMOVDconst [math.Inf(-1)]))
+ // result: (SEQZ (ANDI <typ.Int64> [0b00_0000_0001] (FCLASSD x)))
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
x := v_0
- if v_1.Op != OpRISCV64FMOVDconst {
- continue
- }
- c := auxIntToFloat64(v_1.AuxInt)
- if !(float64ExactBits(c, math.Inf(-1))) {
+ if v_1.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_1.AuxInt) != math.Inf(-1) {
continue
}
v.reset(OpRISCV64SEQZ)
v0 := b.NewValue0(v.Pos, OpRISCV64ANDI, typ.Int64)
- v0.AuxInt = int64ToAuxInt(1)
+ v0.AuxInt = int64ToAuxInt(0b00_0000_0001)
v1 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v1.AddArg(x)
v0.AddArg(v1)
@@ -4179,22 +4144,17 @@
}
break
}
- // match: (FNED x (FMOVDconst [c]))
- // cond: float64ExactBits(c, math.Inf(1))
- // result: (SEQZ (ANDI <typ.Int64> [1<<7] (FCLASSD x)))
+ // match: (FNED x (FMOVDconst [math.Inf(1)]))
+ // result: (SEQZ (ANDI <typ.Int64> [0b00_1000_0000] (FCLASSD x)))
for {
for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
x := v_0
- if v_1.Op != OpRISCV64FMOVDconst {
- continue
- }
- c := auxIntToFloat64(v_1.AuxInt)
- if !(float64ExactBits(c, math.Inf(1))) {
+ if v_1.Op != OpRISCV64FMOVDconst || auxIntToFloat64(v_1.AuxInt) != math.Inf(1) {
continue
}
v.reset(OpRISCV64SEQZ)
v0 := b.NewValue0(v.Pos, OpRISCV64ANDI, typ.Int64)
- v0.AuxInt = int64ToAuxInt(1 << 7)
+ v0.AuxInt = int64ToAuxInt(0b00_1000_0000)
v1 := b.NewValue0(v.Pos, OpRISCV64FCLASSD, typ.Int64)
v1.AddArg(x)
v0.AddArg(v1)
Change information
Files:
- M src/cmd/compile/internal/ssa/_gen/RISCV64.rules
- M src/cmd/compile/internal/ssa/rewrite.go
- M src/cmd/compile/internal/ssa/rewriteRISCV64.go
Change size: M
Delta: 3 files changed, 40 insertions(+), 84 deletions(-)
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Michael Munday (Gerrit)
Nov 3, 2025, 6:18:13 PM (2 days ago) Nov 3
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Michael Munday (Gerrit)
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Michael Pratt (Gerrit)
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Gopher Robot (Gerrit)
Nov 4, 2025, 3:47:49 PM (2 days ago) Nov 4
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Change information
Commit message:
cmd/compile/internal/ssa: simplify riscv64 FCLASSD rewrite rules
We don't need to check that the bit patterns of the constants
match, it is sufficient to just check the constant is equal to the
given value.
While we're here also change the FCLASSD rules to use a bit pattern
for the mask. I think this improves readability, particularly as
more uses of FCLASSD get added (e.g. CL 717560).
These changes should not affect codegen.
Change-Id: I92a6338dc71e6a71e04306f67d7d86016c6e9c47
Reviewed-on: https://go-review.googlesource.com/c/go/+/717580
Reviewed-by: Michael Pratt <mpr...@google.com>
LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <k...@golang.org>
Reviewed-by: Keith Randall <k...@google.com>
Reviewed-by: Keith Randall <k...@golang.org>
Files:
- M src/cmd/compile/internal/ssa/_gen/RISCV64.rules
- M src/cmd/compile/internal/ssa/rewrite.go
- M src/cmd/compile/internal/ssa/rewriteRISCV64.go
Change size: M
Delta: 3 files changed, 40 insertions(+), 84 deletions(-)
Branch: refs/heads/master
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Code-Review: +2 by Keith Randall, +1 by Keith Randall, +1 by Michael Pratt
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