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authorIlya Leoshkevich <iii@linux.ibm.com>2019-02-08 12:39:27 +0000
committerIlya Leoshkevich <iii@gcc.gnu.org>2019-02-08 12:39:27 +0000
commit11719d1474c6dbd574867646b7c53f9719abc178 (patch)
tree2eda6c5ea5df299062509119d9c47bd770d4d319
parent5f5d88d82bcc0d7a483c6872368e66e3961df7ff (diff)
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S/390: Introduce jdd constraint
Implementation of section anchors in S/390 back-end added in r266741 broke jump labels in S/390 Linux kernel [1]. Currently jump labels pass global variable addresses to .quad directive in inline assembly using "X" constraint. In the past this used to produce regular symbol references, however, after r266741 we sometimes get values like (plus (reg) (const_int)), where (reg) points to a section anchor. Strictly speaking, this is still correct, since "X" accepts anything. Thus, now we need another way to support jump labels. The existing "i" constraint cannot be used, since with -fPIC it must not accept non-local symbols, however, jump labels do require that, e.g. __tracepoint_xdp_exception from kernel proper might be referenced from kernel modules. The existing "ZL" constraint cannot be used for the same reason. The existing "b" constraint cannot be used because of the way expand_asm_stmt works. It deduces whether the constraint allows regs, subregs or mems, and processes asm operands differently based on that. "b" is supposed to accept values like (mem (symbol_ref)), and there appears to be no way to explain to expand_asm_stmt that for "b" mem's address must not be in a register. This patch introduces the new machine-specific constraint named "jdd" - "j" prefix is already used for constants, and "d" stands for "data". It accepts anything that fits into the data section, whether or not this might require a relocation, that is, anything that passes CONSTANT_P check. [1] https://lkml.org/lkml/2019/1/23/346 gcc/ChangeLog: 2019-02-08 Ilya Leoshkevich <iii@linux.ibm.com> * config/s390/constraints.md (jdd): New constraint. gcc/testsuite/ChangeLog: 2019-02-08 Ilya Leoshkevich <iii@linux.ibm.com> * gcc.target/s390/jump-label.c: New test. From-SVN: r268688
-rw-r--r--gcc/ChangeLog4
-rw-r--r--gcc/config/s390/constraints.md17
-rw-r--r--gcc/testsuite/ChangeLog4
-rw-r--r--gcc/testsuite/gcc.target/s390/jump-label.c19
4 files changed, 44 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5e826d0..ef22ae2 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2019-02-08 Ilya Leoshkevich <iii@linux.ibm.com>
+
+ * config/s390/constraints.md (jdd): New constraint.
+
2019-02-08 H.J. Lu <hongjiu.lu@intel.com>
PR target/89229
diff --git a/gcc/config/s390/constraints.md b/gcc/config/s390/constraints.md
index 688dd96..4055cbc 100644
--- a/gcc/config/s390/constraints.md
+++ b/gcc/config/s390/constraints.md
@@ -37,6 +37,7 @@
;; jKK: constant vector with all elements having the same value and
;; matching K constraint
;; jm6: An integer operand with the lowest order 6 bits all ones.
+;; jdd: A constant operand that fits into the data section.
;; t -- Access registers 36 and 37.
;; v -- Vector registers v0-v31.
;; C -- A signed 8-bit constant (-128..127)
@@ -567,3 +568,19 @@
(define_constraint "ZL"
"LARL operand when in 64-bit mode, otherwise nothing."
(match_test "TARGET_64BIT && larl_operand (op, VOIDmode)"))
+
+;; This constraint must behave like "i", in particular, the matching values
+;; must never be placed into registers or memory by
+;; cfgexpand.c:expand_asm_stmt. It could be straightforward to start its name
+;; with a letter from genpreds.c:const_int_constraints, however it would
+;; require using (match_code "const_int"), which is infeasible. To achieve the
+;; same effect, that is, setting maybe_allows_reg and maybe_allows_mem to false
+;; in genpreds.c:add_constraint, we explicitly exclude reg, subreg and mem
+;; codes.
+(define_constraint "jdd"
+ "A constant operand that fits into the data section.
+ Usage of this constraint might produce a relocation."
+ (and (not (match_code "reg"))
+ (not (match_code "subreg"))
+ (not (match_code "mem"))
+ (match_test "CONSTANT_P (op)")))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 4174857..53ad08a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-02-08 Ilya Leoshkevich <iii@linux.ibm.com>
+
+ * gcc.target/s390/jump-label.c: New test.
+
2019-02-08 Richard Biener <rguenther@suse.de>
PR testsuite/89250
diff --git a/gcc/testsuite/gcc.target/s390/jump-label.c b/gcc/testsuite/gcc.target/s390/jump-label.c
new file mode 100644
index 0000000..3de73f6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/jump-label.c
@@ -0,0 +1,19 @@
+/* Test jdd constraint, which is used for linux kernel jump labels. */
+
+/* { dg-do link } */
+/* { dg-options "-O2 -fPIC -shared" } */
+
+__attribute__ ((visibility ("default"))) extern int i;
+
+void f (void)
+{
+ asm goto (".pushsection foo\n"
+#if defined(__s390x__)
+ ".quad %0-.\n"
+#else
+ ".long %0-.\n"
+#endif
+ ".popsection\n"
+ : : "jdd" (&i) : : l);
+l:;
+}