cmd/compile: add handling for new floating-point comparisons flags

The CL 164718 adds new condition flags for floating-point comparisons
in arm64 backend, but dose not add the handling in rewrite.go for
corresponding Ops, which causes issue 30679. And this CL fixes this
issue.

Fixes #30679

Change-Id: I8acc749f78227c3e9e74fa7938f05fb442fb62c6
Reviewed-on: https://go-review.googlesource.com/c/go/+/166579Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/ssa/rewrite.go

@@ -730,6 +730,14 @@ func arm64Negate(op Op) Op {
 		return OpARM64NotEqual
 	case OpARM64NotEqual:
 		return OpARM64Equal
+	case OpARM64LessThanF:
+		return OpARM64GreaterEqualF
+	case OpARM64GreaterThanF:
+		return OpARM64LessEqualF
+	case OpARM64LessEqualF:
+		return OpARM64GreaterThanF
+	case OpARM64GreaterEqualF:
+		return OpARM64LessThanF
 	default:
 		panic("unreachable")
 	}
@@ -762,6 +770,14 @@ func arm64Invert(op Op) Op {
 		return OpARM64LessEqualU
 	case OpARM64Equal, OpARM64NotEqual:
 		return op
+	case OpARM64LessThanF:
+		return OpARM64GreaterThanF
+	case OpARM64GreaterThanF:
+		return OpARM64LessThanF
+	case OpARM64LessEqualF:
+		return OpARM64GreaterEqualF
+	case OpARM64GreaterEqualF:
+		return OpARM64LessEqualF
 	default:
 		panic("unreachable")
 	}

test/fixedbugs/issue30679.go

+// compile
+
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+	var f float64
+	var p, q *float64
+
+	p = &f
+	if *q > 0 {
+		p = q
+	}
+	_ = *p
+}