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cmd/compile: defer lowering OANDNOT until SSA

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Currently, "x &^ y" gets rewriten into "x & ^y" during walk. It adds
unnecessary complexity to other parts, which must aware about this.

Instead, we can just implement "&^" in the conversion to SSA, so "&^"
can be handled like other binary operators.

However, this CL does not pass toolstash-check. It seems that implements
"&^" in the conversion to SSA causes registers allocation change.

With the parent:

obj: 00212 (.../src/runtime/complex.go:47)    MOVQ    X0, AX
obj: 00213 (.../src/runtime/complex.go:47)    BTRQ    $63, AX
obj: 00214 (.../src/runtime/complex.go:47)    MOVQ    "".n(SP), CX
obj: 00215 (.../src/runtime/complex.go:47)    MOVQ    $-9223372036854775808, DX
obj: 00216 (.../src/runtime/complex.go:47)    ANDQ    DX, CX
obj: 00217 (.../src/runtime/complex.go:47)    ORQ AX, CX

With this CL:

obj: 00212 (.../src/runtime/complex.go:47)    MOVQ    X0, AX
obj: 00213 (.../src/runtime/complex.go:47)    BTRQ    $63, AX
obj: 00214 (.../src/runtime/complex.go:47)    MOVQ    $-9223372036854775808, CX
obj: 00215 (.../src/runtime/complex.go:47)    MOVQ    "".n(SP), DX
obj: 00216 (.../src/runtime/complex.go:47)    ANDQ    CX, DX
obj: 00217 (.../src/runtime/complex.go:47)    ORQ AX, DX

Change-Id: I80acf8496a91be4804fb7ef3df04c19baae2754c
Reviewed-on: https://go-review.googlesource.com/c/go/+/264660
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Cuong Manh Le 2020-10-24 10:40:09 +07:00
parent fb7134e4e3
commit a19cf510af
4 changed files with 23 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
src/cmd/compile/internal/gc/ssa.go
View File

@ -2472,6 +2472,11 @@ func (s *state) expr(n *Node) *ssa.Value {
a := s.expr(n.Left)
b := s.expr(n.Right)
return s.newValue2(s.ssaOp(n.Op, n.Type), a.Type, a, b)
case OANDNOT:
a := s.expr(n.Left)
b := s.expr(n.Right)
b = s.newValue1(s.ssaOp(OBITNOT, b.Type), b.Type, b)
return s.newValue2(s.ssaOp(OAND, n.Type), a.Type, a, b)
case OLSH, ORSH:
a := s.expr(n.Left)
b := s.expr(n.Right)

2
src/cmd/compile/internal/gc/syntax.go
View File

@ -142,7 +142,7 @@ const (
_, _ // second nodeInitorder bit
_, nodeHasBreak
_, nodeNoInline // used internally by inliner to indicate that a function call should not be inlined; set for OCALLFUNC and OCALLMETH only
_, nodeImplicit // implicit OADDR or ODEREF; ++/-- statement represented as OASOP; or ANDNOT lowered to OAND
_, nodeImplicit // implicit OADDR or ODEREF; ++/-- statement represented as OASOP
_, nodeIsDDD // is the argument variadic
_, nodeDiag // already printed error about this
_, nodeColas // OAS resulting from :=

30
src/cmd/compile/internal/gc/walk.go
View File

@ -474,7 +474,7 @@ opswitch:
ODEREF, OSPTR, OITAB, OIDATA, OADDR:
n.Left = walkexpr(n.Left, init)
case OEFACE, OAND, OSUB, OMUL, OADD, OOR, OXOR, OLSH, ORSH:
case OEFACE, OAND, OANDNOT, OSUB, OMUL, OADD, OOR, OXOR, OLSH, ORSH:
n.Left = walkexpr(n.Left, init)
n.Right = walkexpr(n.Right, init)
@ -965,14 +965,6 @@ opswitch:
fn := basicnames[param] + "to" + basicnames[result]
n = conv(mkcall(fn, types.Types[result], init, conv(n.Left, types.Types[param])), n.Type)
case OANDNOT:
n.Left = walkexpr(n.Left, init)
n.Op = OAND
n.SetImplicit(true) // for walkCheckPtrArithmetic
n.Right = nod(OBITNOT, n.Right, nil)
n.Right = typecheck(n.Right, ctxExpr)
n.Right = walkexpr(n.Right, init)
case ODIV, OMOD:
n.Left = walkexpr(n.Left, init)
n.Right = walkexpr(n.Right, init)
@ -3609,14 +3601,20 @@ func bounded(n *Node, max int64) bool {
}
switch n.Op {
case OAND:
case OAND, OANDNOT:
v := int64(-1)
if smallintconst(n.Left) {
switch {
case smallintconst(n.Left):
v = n.Left.Int64Val()
} else if smallintconst(n.Right) {
case smallintconst(n.Right):
v = n.Right.Int64Val()
if n.Op == OANDNOT {
v = ^v
if !sign {
v &= 1<<uint(bits) - 1
}
}
}
if 0 <= v && v < max {
return true
}
@ -4045,12 +4043,8 @@ func walkCheckPtrArithmetic(n *Node, init *Nodes) *Node {
case OADD:
walk(n.Left)
walk(n.Right)
case OSUB:
case OSUB, OANDNOT:
walk(n.Left)
case OAND:
if n.Implicit() { // was OANDNOT
walk(n.Left)
}
case OCONVNOP:
if n.Left.Type.IsUnsafePtr() {
n.Left = cheapexpr(n.Left, init)

5
test/bounds.go
View File

@ -209,6 +209,11 @@ func main() {
use(a1k[i&^0])
use(a1k[i&^-2]) // ERROR "index bounds check elided"
use(a1k[i&^1])
use(a1k[i8&^0])
use(a1k[i8&^-128]) // ERROR "index bounds check elided"
use(a1k[ui8&^1]) // ERROR "index bounds check elided"
use(a1k[ui16&^0xf000])
use(a1k[ui16&^0xff00]) // ERROR "index bounds check elided"
// Right shift cuts the effective number of bits in the index,
// but only for unsigned (signed stays negative).