[PATCH][arm] PR target/82975: Guard against reg_renumber being NULL in arm.h

[Kyrill Tkachov]

Hi all,

In this bug we ICE when checking REGNO_OK_FOR_INDEX_P on arm during 
pre-IRA scheduling.
This is because REGNO_OK_FOR_INDEX_P ends up checking the reg_renumber 
array.
Before IRA reg_renumber is NULL and thus we segfault.
The fix is to guard the use of reg_renumber in the logic in TEST_REGNO 
in arm.h.
On aarch64, for example, we also guard against the reg_renumber == NULL 
case.
This fixes the ICE. I also remove the part of the comment that muses on 
when reg_renumber
is available as with this patch it should now be safe to use at any point.

Bootstrapped and tested on arm-none-linux-gnueabihf.

Committed to trunk as r255830.

Thanks,
Kyrill

2017-12-19  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    PR target/82975
    * config/arm/arm.h (TEST_REGNO): Check reg_renumber is set before
    accessing it.  Adjust comment.

2017-12-19  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    PR target/82975
    * gcc.dg/pr82975.c: New test.
commit 57beb9c5faf502ef6fb5a40bc0fa54541238b0c1
Author: Kyrylo Tkachov <kyrylo.tkac...@arm.com>
Date:   Mon Dec 18 12:06:55 2017 +0000

    [arm] PR target/82975: Guard against reg_renumber being NULL in arm.h

diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 47931e1..90478fc 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -1626,7 +1626,8 @@ enum arm_auto_incmodes
    has been allocated, which happens in reginfo.c during register
    allocation.  */
 #define TEST_REGNO(R, TEST, VALUE) \
-  ((R TEST VALUE) || ((unsigned) reg_renumber[R] TEST VALUE))
+  ((R TEST VALUE)	\
+    || (reg_renumber && ((unsigned) reg_renumber[R] TEST VALUE)))
 
 /* Don't allow the pc to be used.  */
 #define ARM_REGNO_OK_FOR_BASE_P(REGNO)			\
diff --git a/gcc/testsuite/gcc.dg/pr82975.c b/gcc/testsuite/gcc.dg/pr82975.c
new file mode 100644
index 0000000..e6c13bc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr82975.c
@@ -0,0 +1,19 @@
+/* PR target/82975.  */
+/* { dg-do compile } */
+/* { dg-options "-mtune=cortex-a57 -fno-sched-pressure -O2" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+struct S1
+{
+  char pad1;
+  char val;
+  short pad2;
+};
+
+extern char t[256];
+
+void foo (struct S1 a, size_t i)
+{
+  t[i] = a.val;
+}