IBM zSystems: Fix function_ok_for_sibcall [PR106355]

For a parameter with BLKmode we cannot use REG_NREGS in order to
determine the number of consecutive registers.  Streamlined this with
the implementation of s390_function_arg.

Fix some indentation whitespace, too.

gcc/ChangeLog:

	PR target/106355
	* config/s390/s390.cc (s390_call_saved_register_used): For a
	parameter with BLKmode fix determining number of consecutive
	registers.

gcc/testsuite/ChangeLog:

	* gcc.target/s390/pr106355.h: Common code for new tests.
	* gcc.target/s390/pr106355-1.c: New test.
	* gcc.target/s390/pr106355-2.c: New test.
	* gcc.target/s390/pr106355-3.c: New test.

(cherry picked from commit cb994acc08b67f26a54e7c5dc1f4995a2ce24d98)

4 files changed, 76 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.target/s390/pr106355-1.c b/gcc/testsuite/gcc.target/s390/pr106355-1.c
new file mode 100644
index 0000000..1ec0f6b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/pr106355-1.c
@@ -0,0 +1,42 @@
+/* { dg-do compile } */
+/* { dg-options "-foptimize-sibling-calls" } */
+/* { dg-final { scan-assembler {brasl\t%r\d+,bar4} } } */
+/* { dg-final { scan-assembler {brasl\t%r\d+,bar8} } } */
+
+/* Parameter E is passed in GPR 6 which is call-saved which prohibits
+   sibling call optimization.  This must hold true also if the mode of the
+   parameter is BLKmode.  */
+
+/* 4 byte */
+
+typedef struct
+{
+  char x;
+  char y[3];
+} t4;
+
+extern t4 e4;
+
+extern void bar4 (int a, int b, int c, int d, t4 e4);
+
+void foo4 (int a, int b, int c, int d)
+{
+  bar4 (a, b, c, d, e4);
+}
+
+/* 8 byte */
+
+typedef struct
+{
+  short x;
+  char y[6];
+} t8;
+
+extern t8 e8;
+
+extern void bar8 (int a, int b, int c, int d, t8 e8);
+
+void foo8 (int a, int b, int c, int d)
+{
+  bar8 (a, b, c, d, e8);
+}
diff --git a/gcc/testsuite/gcc.target/s390/pr106355-2.c b/gcc/testsuite/gcc.target/s390/pr106355-2.c
new file mode 100644
index 0000000..ddbdba5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/pr106355-2.c
@@ -0,0 +1,8 @@
+/* { dg-do compile { target { s390-*-* } } } */
+/* { dg-options "-foptimize-sibling-calls -mzarch" } */
+/* { dg-final { scan-assembler {brasl\t%r\d+,bar} } } */
+
+/* This tests function s390_call_saved_register_used where
+   GET_CODE (parm_rtx) == PARALLEL holds.  */
+
+#include "pr106355.h"
diff --git a/gcc/testsuite/gcc.target/s390/pr106355-3.c b/gcc/testsuite/gcc.target/s390/pr106355-3.c
new file mode 100644
index 0000000..39daea44
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/pr106355-3.c
@@ -0,0 +1,8 @@
+/* { dg-do compile { target { s390-*-* } } } */
+/* { dg-options "-foptimize-sibling-calls -mesa" } */
+/* { dg-final { scan-assembler {brasl\t%r\d+,bar} } } */
+
+/* This tests function s390_call_saved_register_used where
+   REG_P (parm_rtx) and nregs == 2 holds.  */
+
+#include "pr106355.h"
diff --git a/gcc/testsuite/gcc.target/s390/pr106355.h b/gcc/testsuite/gcc.target/s390/pr106355.h
new file mode 100644
index 0000000..362908e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/pr106355.h
@@ -0,0 +1,18 @@
+/* For the S/390 ABI parameter D is passed in GPR 5 and 6 and the latter is
+   call-saved which prohibits sibling call optimization.  This must hold true
+   also if the mode of the parameter is BLKmode.  */
+
+typedef struct
+{
+  short x;
+  char y[6];
+} t;
+
+extern t d;
+
+extern void bar (int a, int b, int c, t d);
+
+void foo (int a, int b, int c)
+{
+  bar (a, b, c, d);
+}