code review 6733055: cmd/5g, cmd/6g: fix out of registers with array indexing.

test/torture.go

 // compile
 
 // Copyright 2012 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.
 
 // Various tests for expressions with high complexity.
 
 package main
 
@@ skipping 98 matching lines @@
                 m[0][2]*m[1][3]*m[2][0]*m[3][1] -
                 m[0][2]*m[1][3]*m[2][1]*m[3][0] -
                 m[0][3]*m[1][0]*m[2][1]*m[3][2] +
                 m[0][3]*m[1][0]*m[2][2]*m[3][1] +
                 m[0][3]*m[1][1]*m[2][0]*m[3][2] -
                 m[0][3]*m[1][1]*m[2][2]*m[3][0] -
                 m[0][3]*m[1][2]*m[2][0]*m[3][1] +
                 m[0][3]*m[1][2]*m[2][1]*m[3][0]
 }
 
+type A []A
+
+// A sequence of constant indexings.
+func IndexChain1(s A) A {
+        return s[0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0]
+}
+
+// A sequence of non-constant indexings.
+func IndexChain2(s A, i int) A {
+        return s[i][i][i][i][i][i][i][i][i][i][i][i][i][i][i][i]
+}
+
+// Another sequence of indexings.
+func IndexChain3(s []int) int {
+        return s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[s[0]]]]]]]]]]]]]]]]]]]]]
+}
+
 // A right-leaning tree of byte multiplications.
 func righttree(a, b, c, d uint8) uint8 {
         return a * (b * (c * (d *
                 (a * (b * (c * (d *
                         (a * (b * (c * (d *
                                 (a * (b * (c * (d *
                                         (a * (b * (c * (d *
                                                 a * (b * (c * d)))))))))))))))))))))
 
 }
@@ skipping 181 matching lines @@
                         (a / (b / (a / (b /
                                 (a / (b / (a / (b /
                                         (a / (b / (a / b))))))))))))))))))
 }
 
 func ChainDivConst(a int) int {
         return a / 17 / 17 / 17 /
                 17 / 17 / 17 / 17 /
                 17 / 17 / 17 / 17
 }