cmd/compile: extend all the cmov into math generic rules with their contrary

If the bool comes from a local operation this is foldable into the comparison.
  if a == b {
  } else {
    x++
  }
becomes:
  x += !(a == b)
becomes:
  x += a != b

If the bool is passed in or loaded rather than being locally computed
this adds an extra XOR ^1 to invert it.

But at worst it should make the math equal to the compute + CMP + CMOV
which is a tie on modern CPUs which can execute CMOV on all int ALUs
and a win on the cheaper or older ones which can't.

Change-Id: Idd2566c7a3826ec432ebfbba7b3898aa0db4b812
Reviewed-on: https://go-review.googlesource.com/c/go/+/760922
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Junyang Shao <shaojunyang@google.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ssa/_gen/generic.rules b/src/cmd/compile/internal/ssa/_gen/generic.rules
index 7dcf818976..e75f371790 100644
--- a/src/cmd/compile/internal/ssa/_gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/_gen/generic.rules
@@ -2300,25 +2300,42 @@
 // if b { x++ } => x += b // but not on arm64 because it has CSINC
 (CondSelect (Add8 <t> x (Const8 [1])) x bool) && config.arch != "arm64" => (Add8 x (CvtBoolToUint8 <t> bool))
 (CondSelect (Add(64|32|16) <t> x (Const(64|32|16) [1])) x bool) && config.arch != "arm64" => (Add(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> bool)))
+// if !b { x++ } => x += !b // but not on arm64 because it has CSINC
+(CondSelect x (Add8 <t> x (Const8 [1])) bool) && config.arch != "arm64" => (Add8 x (CvtBoolToUint8 <t> (Not <bool.Type> bool)))
+(CondSelect x (Add(64|32|16) <t> x (Const(64|32|16) [1])) bool) && config.arch != "arm64" => (Add(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool))))
 
 // if b { x-- } => x -= b
 (CondSelect (Add8 <t> x (Const8 [-1])) x bool) => (Sub8 x (CvtBoolToUint8 <t> bool))
 (CondSelect (Add(64|32|16) <t> x (Const(64|32|16) [-1])) x bool) => (Sub(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> bool)))
+// if !b { x-- } => x -= !b
+(CondSelect x (Add8 <t> x (Const8 [-1])) bool) => (Sub8 x (CvtBoolToUint8 <t> (Not <bool.Type> bool)))
+(CondSelect x (Add(64|32|16) <t> x (Const(64|32|16) [-1])) bool) => (Sub(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool))))
 
 // if b { x <<= 1 } => x <<= b
 (CondSelect (Lsh(64|32|16|8)x64 x (Const64 [1])) x bool) => (Lsh(64|32|16|8)x8 [true] x (CvtBoolToUint8 <types.Types[types.TUINT8]> bool))
+// if !b { x <<= 1 } => x <<= !b
+(CondSelect x (Lsh(64|32|16|8)x64 x (Const64 [1])) bool) => (Lsh(64|32|16|8)x8 [true] x (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool)))
 
 // if b { x >>= 1 } => x >>= b
 (CondSelect (Rsh(64|32|16|8)x64 x (Const64 [1])) x bool) => (Rsh(64|32|16|8)x8 [true] x (CvtBoolToUint8 <types.Types[types.TUINT8]> bool))
 (CondSelect (Rsh(64|32|16|8)Ux64 x (Const64 [1])) x bool) => (Rsh(64|32|16|8)Ux8 [true] x (CvtBoolToUint8 <types.Types[types.TUINT8]> bool))
+// if !b { x >>= 1 } => x >>= !b
+(CondSelect x (Rsh(64|32|16|8)x64 x (Const64 [1])) bool) => (Rsh(64|32|16|8)x8 [true] x (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool)))
+(CondSelect x (Rsh(64|32|16|8)Ux64 x (Const64 [1])) bool) => (Rsh(64|32|16|8)Ux8 [true] x (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool)))
 
 // if b { x |= 1 } => x |= b
 (CondSelect (Or8 <t> x (Const8 [1])) x bool) => (Or8 x (CvtBoolToUint8 <t> bool))
 (CondSelect (Or(64|32|16) <t> x (Const(64|32|16) [1])) x bool) => (Or(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> bool)))
+// if !b { x |= 1 } => x |= !b
+(CondSelect x (Or8 <t> x (Const8 [1])) bool) => (Or8 x (CvtBoolToUint8 <t> (Not <bool.Type> bool)))
+(CondSelect x (Or(64|32|16) <t> x (Const(64|32|16) [1])) bool) => (Or(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool))))
 
 // if b { x ^= 1 } => x ^= b
 (CondSelect (Xor8 <t> x (Const8 [1])) x bool) => (Xor8 x (CvtBoolToUint8 <t> bool))
 (CondSelect (Xor(64|32|16) <t> x (Const(64|32|16) [1])) x bool) => (Xor(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> bool)))
+// if !b { x ^= 1 } => x ^= !b
+(CondSelect x (Xor8 <t> x (Const8 [1])) bool) => (Xor8 x (CvtBoolToUint8 <t> (Not <bool.Type> bool)))
+(CondSelect x (Xor(64|32|16) <t> x (Const(64|32|16) [1])) bool) => (Xor(64|32|16) x (ZeroExt8to(64|32|16) <t> (CvtBoolToUint8 <types.Types[types.TUINT8]> (Not <bool.Type> bool))))
 
 // bool(int(x)) => x
 (Neq8                                (CvtBoolToUint8 x)  (Const8          [0])) => x