tree 131e5ce6fed36142a3eb9240ce1c89d1872d934c
parent 1f035d036c2a49c1b858af3260552ccaac80858d
author Cherry Zhang <cherryyz@google.com> 1546450075 -0500
committer Cherry Zhang <cherryyz@google.com> 1546457286 +0000

cmd/compile: fix deriving from x+d >= w on overflow in prove pass

In the case of x+d >= w, where d and w are constants, we are
deriving x is within the bound of min=w-d and max=maxInt-d. When
there is an overflow (min >= max), we know only one of x >= min
or x <= max is true, and we derive this by excluding the other.
When excluding x >= min, we did not consider the equal case, so
we could incorrectly derive x <= max when x == min.

Fixes #29502.

Change-Id: Ia9f7d814264b1a3ddf78f52e2ce23377450e6e8a
Reviewed-on: https://go-review.googlesource.com/c/156019
Reviewed-by: David Chase <drchase@google.com>