cmd/compile: absorb more Not ops into Neq* and Eq* ops

We absorbed Not into most integer comparisons but not into pointer
and floating point equality checks.

The new cases trigger more than 300 times during make.bash.

Change-Id: I77c6b31fcacde10da5470b73fc001a19521ce78d
Reviewed-on: https://go-review.googlesource.com/c/go/+/200618
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -260,8 +260,8 @@
 (Sub8  x (Const8  <t> [c])) && x.Op != OpConst8  -> (Add8  (Const8  <t> [int64(int8(-c))]) x)
 
 // fold negation into comparison operators
-(Not (Eq(64|32|16|8|B) x y)) -> (Neq(64|32|16|8|B) x y)
-(Not (Neq(64|32|16|8|B) x y)) -> (Eq(64|32|16|8|B) x y)
+(Not (Eq(64|32|16|8|B|Ptr|64F|32F) x y)) -> (Neq(64|32|16|8|B|Ptr|64F|32F) x y)
+(Not (Neq(64|32|16|8|B|Ptr|64F|32F) x y)) -> (Eq(64|32|16|8|B|Ptr|64F|32F) x y)
 
 (Not (Greater(64|32|16|8) x y)) -> (Leq(64|32|16|8) x y)
 (Not (Greater(64|32|16|8)U x y)) -> (Leq(64|32|16|8)U x y)
@@ -273,7 +273,6 @@
 (Not (Leq(64|32|16|8) x y)) -> (Greater(64|32|16|8) x y)
 (Not (Leq(64|32|16|8)U x y)) -> (Greater(64|32|16|8)U x y)
 
-
 // Distribute multiplication c * (d+x) -> c*d + c*x. Useful for:
 // a[i].b = ...; a[i+1].b = ...
 (Mul64 (Const64 <t> [c]) (Add64 <t> (Const64 <t> [d]) x)) ->