testsuite: arm: Check that a far jump is used in thumb1-far-jump-2.c

With the changes in r15-1579-g792f97b44ff, the code used as "padding" in
the test case is optimized way. Prevent this optimization by forcing a
read of the volatile memory.
Also, validate that there is a far jump in the generated assembler.

Without this patch, the generated assembler is reduced to:
f3:
        cmp     r0, #0
        beq     .L1
        ldr     r4, .L6
.L1:
        bx      lr
.L7:
        .align  2
.L6:
        .word   g_0_1

With the patch, the generated assembler is:
f3:
        movs    r2, #1
        ldr     r3, .L6
        push    {lr}
        str     r2, [r3]
        cmp     r0, #0
        bne     .LCB10
        bl      .L1     @far jump
.LCB10:
        b       .L7
.L8:
        .align  2
.L6:
        .word   .LANCHOR0
.L7:
        str     r2, [r3]
        ...
        str     r2, [r3]
.L1:
        pop     {pc}

gcc/testsuite/ChangeLog:

	* gcc.target/arm/thumb1-far-jump-2.c: Write to volatile memmory
	in macro to avoid optimization.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>

Author: Torbjorn-Svensson

gcc/testsuite/gcc.target/arm/thumb1-far-jump-2.c

@@ -5,53 +5,60 @@
 /* { dg-options "-Os" } */
 /* { dg-skip-if "" { ! { arm_thumb1 } } } */
 
-volatile register int r4 asm ("r4");
+volatile int r4;
+
+#define GO() \
+  r4 = 1;
+
+#define GO8() \
+  GO() \
+  GO() \
+  GO() \
+  GO() \
+  GO() \
+  GO() \
+  GO() \
+  GO()
+
+#define GO32() \
+  GO8() \
+  GO8() \
+  GO8() \
+  GO8()
+
+#define GO128() \
+  GO32() \
+  GO32() \
+  GO32() \
+  GO32()
+
+#define GO512() \
+  GO128() \
+  GO128() \
+  GO128() \
+  GO128()
+
+#define GO1018() \
+  GO512() \
+  GO128() \
+  GO128() \
+  GO128() \
+  GO32() \
+  GO32() \
+  GO32() \
+  GO8() \
+  GO8() \
+  GO8() \
+  GO() \
+  GO()
+
 void f3(int i)
 {
-#define GO(n) \
-  extern volatile int g_##n; \
-  r4=(int)&g_##n;
-
-#define GO8(n) \
-  GO(n##_0) \
-  GO(n##_1) \
-  GO(n##_2) \
-  GO(n##_3) \
-  GO(n##_4) \
-  GO(n##_5) \
-  GO(n##_6) \
-  GO(n##_7)
-
-#define GO64(n) \
-  GO8(n##_0) \
-  GO8(n##_1) \
-  GO8(n##_2) \
-  GO8(n##_3) \
-  GO8(n##_4) \
-  GO8(n##_5) \
-  GO8(n##_6) \
-  GO8(n##_7) \
-
-#define GO498(n) \
-  GO64(n##_0) \
-  GO64(n##_1) \
-  GO64(n##_2) \
-  GO64(n##_3) \
-  GO64(n##_4) \
-  GO64(n##_5) \
-  GO64(n##_6) \
-  GO8(n##_0) \
-  GO8(n##_1) \
-  GO8(n##_2) \
-  GO8(n##_3) \
-  GO8(n##_4) \
-  GO8(n##_5) \
-  GO(n##_0) \
-  GO(n##_1) \
-
+  GO();
   if (i) {
-    GO498(0);
+    GO1018();
   }
 }
 
-/* { dg-final { scan-assembler "push.*lr" } } */
+/* { dg-final { scan-assembler "\tpush.*lr" } } */
+/* { dg-final { scan-assembler "\tbl\t\\.L\[0-9\]+\t@far jump" } } */