cmd/compile: remove broken LEA "optimization"

CL 440035 added rewrite rules to simplify "costly" LEA
instructions, but the types in the rewrites were wrong and
the code would go bad if the wrong-typed register was spilled.

CL 482536 attempted to fix this by correcting the type in the
rewrite, but that "fix" broke something on windows-amd64-race.

Instead / for-now, remove the offending rewrite rules.

Updates golang#21735.
Fixes golang#59432.

Change-Id: I0497c42db414f2055e1378e0a53e2bceee9cd5d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/482820
Run-TryBot: David Chase <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: dr2chase

src/cmd/compile/internal/ssa/_gen/AMD64latelower.rules

@@ -2,14 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// split 3 operand LEA.
-// Note: Don't split pointer computations in order to avoid invalid pointers.
-(LEA(Q|L|W)1 <t> [c] {s} x y) &&  isPtr(x.Type) && c != 0 && s == nil => (ADD(Q|L|L) x (ADD(Q|L|L)const <y.Type> [c] y))
-(LEA(Q|L|W)1 <t> [c] {s} x y) && !isPtr(x.Type) && c != 0 && s == nil => (ADD(Q|L|L) y (ADD(Q|L|L)const <x.Type> [c] x))
-(LEA(Q|L|W)2 <t> [c] {s} x y) && !isPtr(t)      && c != 0 && s == nil => (ADD(Q|L|L)const [c] (LEA(Q|L|W)2 <x.Type> x y))
-(LEA(Q|L|W)4 <t> [c] {s} x y) && !isPtr(t)      && c != 0 && s == nil => (ADD(Q|L|L)const [c] (LEA(Q|L|W)4 <x.Type> x y))
-(LEA(Q|L|W)8 <t> [c] {s} x y) && !isPtr(t)      && c != 0 && s == nil => (ADD(Q|L|L)const [c] (LEA(Q|L|W)8 <x.Type> x y))
-
 // Prefer SARX/SHLX/SHRX instruction because it has less register restriction on the shift input.
 (SAR(Q|L) x y) && buildcfg.GOAMD64 >= 3 => (SARX(Q|L) x y)
 (SHL(Q|L) x y) && buildcfg.GOAMD64 >= 3 => (SHLX(Q|L) x y)