cmd/compile: add constant folding for bits.Add64

Change-Id: I0ed4ebeaaa68e274e5902485ccc1165c039440bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/656275
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>

diff --git a/src/cmd/compile/internal/ssa/_gen/generic.rules b/src/cmd/compile/internal/ssa/_gen/generic.rules
index e671568d79740ccbf53ddef000932183bf224c51..02e4290b9d6abf0227ef782cceb1a3214ac717a7 100644 (file)
--- a/src/cmd/compile/internal/ssa/_gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/_gen/generic.rules
@@ -74,6 +74,7 @@
 (PopCount32 (Const32 [c])) && config.PtrSize == 4 => (Const32 [int32(bits.OnesCount32(uint32(c)))])
 (PopCount16 (Const16 [c])) && config.PtrSize == 4 => (Const32 [int32(bits.OnesCount16(uint16(c)))])
 (PopCount8  (Const8  [c])) && config.PtrSize == 4 => (Const32 [int32(bits.OnesCount8(uint8(c)))])
+(Add64carry (Const64 <t> [x]) (Const64 [y]) (Const64 [c])) && c >= 0 && c <= 1 => (MakeTuple (Const64 <t> [bitsAdd64(x, y, c).sum]) (Const64 <t> [bitsAdd64(x, y, c).carry]))
 
 (Trunc16to8  (ZeroExt8to16  x)) => x
 (Trunc32to8  (ZeroExt8to32  x)) => x

diff --git a/src/cmd/compile/internal/ssa/rewrite.go b/src/cmd/compile/internal/ssa/rewrite.go
index eb523675b15a6d09f4436d0259769d7abf84422a..b441d68536deec1311afe283d78ee899ad483fff 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewrite.go
+++ b/src/cmd/compile/internal/ssa/rewrite.go
@@ -2554,3 +2554,9 @@ func isDirectIface2(v *Value, depth int) bool {
        }
        return false
 }
+
+func bitsAdd64(x, y, carry int64) (r struct{ sum, carry int64 }) {
+       s, c := bits.Add64(uint64(x), uint64(y), uint64(carry))
+       r.sum, r.carry = int64(s), int64(c)
+       return
+}

diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index d5a50f42049188739f3286c50f5cc4cf31f1b09c..6f3cd659ef5c4c467ab0adedee9155e3c1ef9454 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -20,6 +20,8 @@ func rewriteValuegeneric(v *Value) bool {
                return rewriteValuegeneric_OpAdd64(v)
        case OpAdd64F:
                return rewriteValuegeneric_OpAdd64F(v)
+       case OpAdd64carry:
+               return rewriteValuegeneric_OpAdd64carry(v)
        case OpAdd8:
                return rewriteValuegeneric_OpAdd8(v)
        case OpAddPtr:
@@ -2376,6 +2378,44 @@ func rewriteValuegeneric_OpAdd64F(v *Value) bool {
        }
        return false
 }
+func rewriteValuegeneric_OpAdd64carry(v *Value) bool {
+       v_2 := v.Args[2]
+       v_1 := v.Args[1]
+       v_0 := v.Args[0]
+       b := v.Block
+       // match: (Add64carry (Const64 <t> [x]) (Const64 [y]) (Const64 [c]))
+       // cond: c >= 0 && c <= 1
+       // result: (MakeTuple (Const64 <t> [bitsAdd64(x, y, c).sum]) (Const64 <t> [bitsAdd64(x, y, c).carry]))
+       for {
+               for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
+                       if v_0.Op != OpConst64 {
+                               continue
+                       }
+                       t := v_0.Type
+                       x := auxIntToInt64(v_0.AuxInt)
+                       if v_1.Op != OpConst64 {
+                               continue
+                       }
+                       y := auxIntToInt64(v_1.AuxInt)
+                       if v_2.Op != OpConst64 {
+                               continue
+                       }
+                       c := auxIntToInt64(v_2.AuxInt)
+                       if !(c >= 0 && c <= 1) {
+                               continue
+                       }
+                       v.reset(OpMakeTuple)
+                       v0 := b.NewValue0(v.Pos, OpConst64, t)
+                       v0.AuxInt = int64ToAuxInt(bitsAdd64(x, y, c).sum)
+                       v1 := b.NewValue0(v.Pos, OpConst64, t)
+                       v1.AuxInt = int64ToAuxInt(bitsAdd64(x, y, c).carry)
+                       v.AddArg2(v0, v1)
+                       return true
+               }
+               break
+       }
+       return false
+}
 func rewriteValuegeneric_OpAdd8(v *Value) bool {
        v_1 := v.Args[1]
        v_0 := v.Args[0]