unssa: track uses when replacing a phi node

unssa: track uses when replacing a phi node

Hello,

attached are patch, testing input for test-unssa and its outputs before patch
and after patch. Thanks in advance for considering the patch!

Kamil
test:
.L0x7f9fb2030010
	<entry-point>
	phisrc.32   %phi2(ptr) <- %arg1
	br          .L0x7f9fb2030130

.L0x7f9fb2030130
	copy.32     %r1(ptr) <- %r5(ptr)
	br          %r1(ptr), .L0x7f9fb2030058, .L0x7f9fb20300e8

.L0x7f9fb2030058
	load.32     %r3 <- 0[%r1(ptr)]
	phisrc.32   %phi3(ptr) <- %r3
	br          .L0x7f9fb2030130

.L0x7f9fb20300e8
	ret
test:
.L0x7f4a7f7f1010
	<entry-point>
	copy.32     %r5(ptr) <- %arg1
	br          .L0x7f4a7f7f1130

.L0x7f4a7f7f1130
	copy.32     %r1(ptr) <- %r5(ptr)
	br          %r1(ptr), .L0x7f4a7f7f1058, .L0x7f4a7f7f10e8

.L0x7f4a7f7f1058
	load.32     %r3 <- 0[%r1(ptr)]
	copy.32     %r5(ptr) <- %r3
	br          .L0x7f4a7f7f1130

.L0x7f4a7f7f10e8
	ret

>From 66a02fa7cec780fc88d6ef4cce7a1e704928808a Mon Sep 17 00:00:00 2001
From: Kamil Dudka <kdudka@redhat.com>
Date: Sun, 9 Aug 2009 10:22:11 +0200
Subject: [PATCH] unssa: track uses when replacing a phi node

The output of test-unssa is inconsistent for a simple test-case without
this patch:

static void test(void **ptr)
{
    while (ptr) {
        ptr = *ptr;
    }
}

Signed-off-by: Kamil Dudka <kdudka@redhat.com>
Signed-off-by: Christopher Li <sparse@chrisli.org>