[PATCH v5 2/2] IBM zSystems: Define CODE_LABEL_BOUNDARY

[Ilya Leoshkevich <iii@linux.ibm.com>]

Currently s390 emits the following sequence to store a frame_pc:

        a:
        .LASANPC0:

                lg      %r1,.L5-.L4(%r13)
                la      %r1,0(%r1,%r12)
                stg     %r1,176(%r11)

        .L5:
                .quad   .LASANPC0@GOTOFF

The reason GOT indirection is used instead of larl is that gcc does not
know that .LASANPC0, being a code label, is aligned on a 2-byte
boundary, and larl can load only even addresses.

Define CODE_LABEL_BOUNDARY in order to get rid of GOT indirection:

                larl    %r1,.LASANPC0
                stg     %r1,176(%r11)

gcc/ChangeLog:

2020-06-30  Ilya Leoshkevich  <iii@linux.ibm.com>

        * config/s390/s390.h (CODE_LABEL_BOUNDARY): Specify that s390
        requires code labels to be aligned on a 2-byte boundary.

gcc/testsuite/ChangeLog:

2019-06-30  Ilya Leoshkevich  <iii@linux.ibm.com>

        * gcc.target/s390/asan-no-gotoff.c: New test.
---
 gcc/config/s390/s390.h                         |  3 +++
 gcc/testsuite/gcc.target/s390/asan-no-gotoff.c | 15 +++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/s390/asan-no-gotoff.c

diff --git a/gcc/config/s390/s390.h b/gcc/config/s390/s390.h
index be566215df2..7d078ce6868 100644
--- a/gcc/config/s390/s390.h
+++ b/gcc/config/s390/s390.h
@@ -368,6 +368,9 @@ extern const char *s390_host_detect_local_cpu (int argc, const char **argv);
 /* Allocation boundary (in *bits*) for the code of a function.  */
 #define FUNCTION_BOUNDARY 64
 
+/* Alignment required for a code label, in bits.  */
+#define CODE_LABEL_BOUNDARY 16
+
 /* There is no point aligning anything to a rounder boundary than this.  */
 #define BIGGEST_ALIGNMENT 64
 
diff --git a/gcc/testsuite/gcc.target/s390/asan-no-gotoff.c b/gcc/testsuite/gcc.target/s390/asan-no-gotoff.c
new file mode 100644
index 00000000000..f555e4e96f8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/asan-no-gotoff.c
@@ -0,0 +1,15 @@
+/* Test that ASAN labels are referenced without unnecessary indirections.  */
+
+/* { dg-do compile } */
+/* { dg-options "-fPIE -O2 -fsanitize=kernel-address --param asan-stack=1" } */
+
+extern void c (int *);
+
+void a ()
+{
+  int b;
+  c (&b);
+}
+
+/* { dg-final { scan-assembler {\tlarl\t%r\d+,\.LASANPC\d+} } } */
+/* { dg-final { scan-assembler-not {\.LASANPC\d+@GOTOFF} } } */
-- 
2.37.2