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cmd/compile: convert SLT/SLTU with constant into immediate form on riscv64

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Convert SLT/SLTU with a suitably valued constant into a SLTI/SLTIU instruction.
This can reduce instructions and avoid register loads. Now that we generate
more SLTI/SLTIU instructions, absorb these into branches when it makes sense
to do so.

Removes more than 800 instructions from the Go binary on linux/riscv64.

Change-Id: I42c4e00486697acd4da7669d441b5690795f18ae
Reviewed-on: https://go-review.googlesource.com/c/go/+/428499
Reviewed-by: Wayne Zuo <wdvxdr@golangcn.org>
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Joedian Reid <joedian@golang.org>
This commit is contained in:
Joel Sing 2022-09-05 03:03:35 +10:00
parent 0ca355318f
commit ba8c94b5f2
2 changed files with 87 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/cmd/compile/internal/ssa/_gen/RISCV64.rules
View File

@ -2,13 +2,6 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Optimizations TODO:
// * Use SLTI and SLTIU for comparisons to constants, instead of SLT/SLTU with constants in registers
// * Use the zero register instead of moving 0 into a register.
// * Add rules to avoid generating a temp bool value for (If (SLT[U] ...) ...).
// * Arrange for non-trivial Zero and Move lowerings to use aligned loads and stores.
// * Avoid using Neq32 for writeBarrier.enabled checks.
// Lowering arithmetic
(Add64 ...) => (ADD ...)
(AddPtr ...) => (ADD ...)
@ -626,6 +619,10 @@
(BNEZ (SLT x y) yes no) => (BLT x y yes no)
(BEQZ (SLTU x y) yes no) => (BGEU x y yes no)
(BNEZ (SLTU x y) yes no) => (BLTU x y yes no)
(BEQZ (SLTI [x] y) yes no) => (BGE y (MOVDconst [x]) yes no)
(BNEZ (SLTI [x] y) yes no) => (BLT y (MOVDconst [x]) yes no)
(BEQZ (SLTIU [x] y) yes no) => (BGEU y (MOVDconst [x]) yes no)
(BNEZ (SLTIU [x] y) yes no) => (BLTU y (MOVDconst [x]) yes no)
// Convert branch with zero to more optimal branch zero.
(BEQ (MOVDconst [0]) cond yes no) => (BEQZ cond yes no)
@ -763,9 +760,11 @@
(AND (MOVDconst [val]) x) && is32Bit(val) => (ANDI [val] x)
(OR (MOVDconst [val]) x) && is32Bit(val) => (ORI [val] x)
(XOR (MOVDconst [val]) x) && is32Bit(val) => (XORI [val] x)
(SLL x (MOVDconst [val])) => (SLLI [int64(val&63)] x)
(SRL x (MOVDconst [val])) => (SRLI [int64(val&63)] x)
(SRA x (MOVDconst [val])) => (SRAI [int64(val&63)] x)
(SLL x (MOVDconst [val])) => (SLLI [int64(val&63)] x)
(SRL x (MOVDconst [val])) => (SRLI [int64(val&63)] x)
(SRA x (MOVDconst [val])) => (SRAI [int64(val&63)] x)
(SLT x (MOVDconst [val])) && val >= -2048 && val <= 2047 => (SLTI [val] x)
(SLTU x (MOVDconst [val])) && val >= -2048 && val <= 2047 => (SLTIU [val] x)
// Convert const subtraction into ADDI with negative immediate, where possible.
(SUB x (MOVDconst [val])) && is32Bit(-val) => (ADDI [-val] x)

78
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -5618,6 +5618,23 @@ func rewriteValueRISCV64_OpRISCV64SLLI(v *Value) bool {
func rewriteValueRISCV64_OpRISCV64SLT(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
// match: (SLT x (MOVDconst [val]))
// cond: val >= -2048 && val <= 2047
// result: (SLTI [val] x)
for {
x := v_0
if v_1.Op != OpRISCV64MOVDconst {
break
}
val := auxIntToInt64(v_1.AuxInt)
if !(val >= -2048 && val <= 2047) {
break
}
v.reset(OpRISCV64SLTI)
v.AuxInt = int64ToAuxInt(val)
v.AddArg(x)
return true
}
// match: (SLT x x)
// result: (MOVDconst [0])
for {
@ -5730,6 +5747,23 @@ func rewriteValueRISCV64_OpRISCV64SLTIU(v *Value) bool {
func rewriteValueRISCV64_OpRISCV64SLTU(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
// match: (SLTU x (MOVDconst [val]))
// cond: val >= -2048 && val <= 2047
// result: (SLTIU [val] x)
for {
x := v_0
if v_1.Op != OpRISCV64MOVDconst {
break
}
val := auxIntToInt64(v_1.AuxInt)
if !(val >= -2048 && val <= 2047) {
break
}
v.reset(OpRISCV64SLTIU)
v.AuxInt = int64ToAuxInt(val)
v.AddArg(x)
return true
}
// match: (SLTU x x)
// result: (MOVDconst [0])
for {
@ -8282,6 +8316,28 @@ func rewriteBlockRISCV64(b *Block) bool {
b.resetWithControl2(BlockRISCV64BGEU, x, y)
return true
}
// match: (BEQZ (SLTI [x] y) yes no)
// result: (BGE y (MOVDconst [x]) yes no)
for b.Controls[0].Op == OpRISCV64SLTI {
v_0 := b.Controls[0]
x := auxIntToInt64(v_0.AuxInt)
y := v_0.Args[0]
v0 := b.NewValue0(b.Pos, OpRISCV64MOVDconst, typ.UInt64)
v0.AuxInt = int64ToAuxInt(x)
b.resetWithControl2(BlockRISCV64BGE, y, v0)
return true
}
// match: (BEQZ (SLTIU [x] y) yes no)
// result: (BGEU y (MOVDconst [x]) yes no)
for b.Controls[0].Op == OpRISCV64SLTIU {
v_0 := b.Controls[0]
x := auxIntToInt64(v_0.AuxInt)
y := v_0.Args[0]
v0 := b.NewValue0(b.Pos, OpRISCV64MOVDconst, typ.UInt64)
v0.AuxInt = int64ToAuxInt(x)
b.resetWithControl2(BlockRISCV64BGEU, y, v0)
return true
}
case BlockRISCV64BGE:
// match: (BGE (MOVDconst [0]) cond yes no)
// result: (BLEZ cond yes no)
@ -8437,6 +8493,28 @@ func rewriteBlockRISCV64(b *Block) bool {
b.resetWithControl2(BlockRISCV64BLTU, x, y)
return true
}
// match: (BNEZ (SLTI [x] y) yes no)
// result: (BLT y (MOVDconst [x]) yes no)
for b.Controls[0].Op == OpRISCV64SLTI {
v_0 := b.Controls[0]
x := auxIntToInt64(v_0.AuxInt)
y := v_0.Args[0]
v0 := b.NewValue0(b.Pos, OpRISCV64MOVDconst, typ.UInt64)
v0.AuxInt = int64ToAuxInt(x)
b.resetWithControl2(BlockRISCV64BLT, y, v0)
return true
}
// match: (BNEZ (SLTIU [x] y) yes no)
// result: (BLTU y (MOVDconst [x]) yes no)
for b.Controls[0].Op == OpRISCV64SLTIU {
v_0 := b.Controls[0]
x := auxIntToInt64(v_0.AuxInt)
y := v_0.Args[0]
v0 := b.NewValue0(b.Pos, OpRISCV64MOVDconst, typ.UInt64)
v0.AuxInt = int64ToAuxInt(x)
b.resetWithControl2(BlockRISCV64BLTU, y, v0)
return true
}
case BlockIf:
// match: (If cond yes no)
// result: (BNEZ (MOVBUreg <typ.UInt64> cond) yes no)