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cmd/compile: optimise branchs on riscv64

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Make use of multi-control values and branch pseudo-instructions to optimise
compiler generated branches.

Change-Id: I7a8bf754db3c2082a390bf6a662ccf18cbcbee39
Reviewed-on: https://go-review.googlesource.com/c/go/+/226400
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joel Sing 2020-03-31 02:04:45 +11:00
parent 000636fdb5
commit 57e32c4fbd
2 changed files with 146 additions and 11 deletions
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32
src/cmd/compile/internal/ssa/gen/RISCV64.rules
View File

@ -445,16 +445,6 @@
(Addr {sym} base) => (MOVaddr {sym} [0] base)
(LocalAddr {sym} base _) => (MOVaddr {sym} base)
// Conditional branches
//
// cond is 1 if true.
//
// TODO(prattmic): RISCV branch instructions take two operands to compare,
// so we could generate more efficient code by computing the condition in the
// branch itself. This should be revisited now that the compiler has support
// for two control values (https://golang.org/cl/196557).
(If cond yes no) => (BNEZ cond yes no)
// Calls
(StaticCall ...) => (CALLstatic ...)
(ClosureCall ...) => (CALLclosure ...)
@ -480,11 +470,31 @@
(AtomicExchange32 ...) => (LoweredAtomicExchange32 ...)
(AtomicExchange64 ...) => (LoweredAtomicExchange64 ...)
// Conditional branches
(If cond yes no) => (BNEZ cond yes no)
// Optimizations
// Absorb SNEZ into branch.
// Absorb SEQZ/SNEZ into branch.
(BEQZ (SEQZ x) yes no) => (BNEZ x yes no)
(BEQZ (SNEZ x) yes no) => (BEQZ x yes no)
(BNEZ (SEQZ x) yes no) => (BEQZ x yes no)
(BNEZ (SNEZ x) yes no) => (BNEZ x yes no)
// Convert BEQZ/BNEZ into more optimal branch conditions.
(BEQZ (SUB x y) yes no) => (BEQ x y yes no)
(BNEZ (SUB x y) yes no) => (BNE x y yes no)
(BEQZ (SLT x y) yes no) => (BGE x y yes no)
(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)
// Convert branch with zero to BEQZ/BNEZ.
(BEQ (MOVDconst [0]) cond yes no) => (BEQZ cond yes no)
(BEQ cond (MOVDconst [0]) yes no) => (BEQZ cond yes no)
(BNE (MOVDconst [0]) cond yes no) => (BNEZ cond yes no)
(BNE cond (MOVDconst [0]) yes no) => (BNEZ cond yes no)
// Store zero
(MOVBstore [off] {sym} ptr (MOVBconst [0]) mem) => (MOVBstorezero [off] {sym} ptr mem)
(MOVHstore [off] {sym} ptr (MOVHconst [0]) mem) => (MOVHstorezero [off] {sym} ptr mem)

125
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -5120,7 +5120,105 @@ func rewriteValueRISCV64_OpZeroExt8to64(v *Value) bool {
}
func rewriteBlockRISCV64(b *Block) bool {
switch b.Kind {
case BlockRISCV64BEQ:
// match: (BEQ (MOVDconst [0]) cond yes no)
// result: (BEQZ cond yes no)
for b.Controls[0].Op == OpRISCV64MOVDconst {
v_0 := b.Controls[0]
if auxIntToInt64(v_0.AuxInt) != 0 {
break
}
cond := b.Controls[1]
b.resetWithControl(BlockRISCV64BEQZ, cond)
return true
}
// match: (BEQ cond (MOVDconst [0]) yes no)
// result: (BEQZ cond yes no)
for b.Controls[1].Op == OpRISCV64MOVDconst {
cond := b.Controls[0]
v_1 := b.Controls[1]
if auxIntToInt64(v_1.AuxInt) != 0 {
break
}
b.resetWithControl(BlockRISCV64BEQZ, cond)
return true
}
case BlockRISCV64BEQZ:
// match: (BEQZ (SEQZ x) yes no)
// result: (BNEZ x yes no)
for b.Controls[0].Op == OpRISCV64SEQZ {
v_0 := b.Controls[0]
x := v_0.Args[0]
b.resetWithControl(BlockRISCV64BNEZ, x)
return true
}
// match: (BEQZ (SNEZ x) yes no)
// result: (BEQZ x yes no)
for b.Controls[0].Op == OpRISCV64SNEZ {
v_0 := b.Controls[0]
x := v_0.Args[0]
b.resetWithControl(BlockRISCV64BEQZ, x)
return true
}
// match: (BEQZ (SUB x y) yes no)
// result: (BEQ x y yes no)
for b.Controls[0].Op == OpRISCV64SUB {
v_0 := b.Controls[0]
y := v_0.Args[1]
x := v_0.Args[0]
b.resetWithControl2(BlockRISCV64BEQ, x, y)
return true
}
// match: (BEQZ (SLT x y) yes no)
// result: (BGE x y yes no)
for b.Controls[0].Op == OpRISCV64SLT {
v_0 := b.Controls[0]
y := v_0.Args[1]
x := v_0.Args[0]
b.resetWithControl2(BlockRISCV64BGE, x, y)
return true
}
// match: (BEQZ (SLTU x y) yes no)
// result: (BGEU x y yes no)
for b.Controls[0].Op == OpRISCV64SLTU {
v_0 := b.Controls[0]
y := v_0.Args[1]
x := v_0.Args[0]
b.resetWithControl2(BlockRISCV64BGEU, x, y)
return true
}
case BlockRISCV64BNE:
// match: (BNE (MOVDconst [0]) cond yes no)
// result: (BNEZ cond yes no)
for b.Controls[0].Op == OpRISCV64MOVDconst {
v_0 := b.Controls[0]
if auxIntToInt64(v_0.AuxInt) != 0 {
break
}
cond := b.Controls[1]
b.resetWithControl(BlockRISCV64BNEZ, cond)
return true
}
// match: (BNE cond (MOVDconst [0]) yes no)
// result: (BNEZ cond yes no)
for b.Controls[1].Op == OpRISCV64MOVDconst {
cond := b.Controls[0]
v_1 := b.Controls[1]
if auxIntToInt64(v_1.AuxInt) != 0 {
break
}
b.resetWithControl(BlockRISCV64BNEZ, cond)
return true
}
case BlockRISCV64BNEZ:
// match: (BNEZ (SEQZ x) yes no)
// result: (BEQZ x yes no)
for b.Controls[0].Op == OpRISCV64SEQZ {
v_0 := b.Controls[0]
x := v_0.Args[0]
b.resetWithControl(BlockRISCV64BEQZ, x)
return true
}
// match: (BNEZ (SNEZ x) yes no)
// result: (BNEZ x yes no)
for b.Controls[0].Op == OpRISCV64SNEZ {
@ -5129,6 +5227,33 @@ func rewriteBlockRISCV64(b *Block) bool {
b.resetWithControl(BlockRISCV64BNEZ, x)
return true
}
// match: (BNEZ (SUB x y) yes no)
// result: (BNE x y yes no)
for b.Controls[0].Op == OpRISCV64SUB {
v_0 := b.Controls[0]
y := v_0.Args[1]
x := v_0.Args[0]
b.resetWithControl2(BlockRISCV64BNE, x, y)
return true
}
// match: (BNEZ (SLT x y) yes no)
// result: (BLT x y yes no)
for b.Controls[0].Op == OpRISCV64SLT {
v_0 := b.Controls[0]
y := v_0.Args[1]
x := v_0.Args[0]
b.resetWithControl2(BlockRISCV64BLT, x, y)
return true
}
// match: (BNEZ (SLTU x y) yes no)
// result: (BLTU x y yes no)
for b.Controls[0].Op == OpRISCV64SLTU {
v_0 := b.Controls[0]
y := v_0.Args[1]
x := v_0.Args[0]
b.resetWithControl2(BlockRISCV64BLTU, x, y)
return true
}
case BlockIf:
// match: (If cond yes no)
// result: (BNEZ cond yes no)