When pushing a value into the literal pool the resulting decl might
get a higher alignment than the original expression depending on how a
target defines CONSTANT_ALIGNMENT. Generating an RTX for the constant
pool access we currently use the alignment from the original
expression. Changed with the attached patch.
This fixes a GCC 6 regression for S/390. For arrays of string
constants as in the attached testcase encode_section_info is not able
to figure out that the constant pool slot is already properly aligned
since the mem_align field in the rtx is not set properly.
Another question is why (at the end of build_constant_desc) we invoke
the encode_section_info hook with the original expression instead of
the newly generated var_decl? I think the hook is supposed to be
invoked with a decl?!
/* Set flags or add text to the name to record information, such as
that it is a local symbol. If the name is changed, the macro
ASM_OUTPUT_LABELREF will have to know how to strip this
information. This call might invalidate our local variable
SYMBOL; we can't use it afterward. */
targetm.encode_section_info (exp, rtl, true);
desc->rtl = rtl;
return desc;
}
Bootstrapped and regtested on x86_64 and s390x.
No regressions.
Ok?
-Andreas-
gcc/ChangeLog:
2016-12-16 Andreas Krebbel <kreb...@linux.vnet.ibm.com>
* varasm.c (build_constant_desc): Use the alignment of the var
decl instead of the original expression.
gcc/testsuite/ChangeLog:
2016-12-16 Andreas Krebbel <kreb...@linux.vnet.ibm.com>
* gcc.target/s390/litpool-str-1.c: New test.
---
gcc/testsuite/gcc.target/s390/litpool-str-1.c | 22 ++++++++++++++++++++++
gcc/varasm.c | 4 ++++
2 files changed, 26 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/s390/litpool-str-1.c
diff --git a/gcc/testsuite/gcc.target/s390/litpool-str-1.c
b/gcc/testsuite/gcc.target/s390/litpool-str-1.c
new file mode 100644
index 0000000..cd921d2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/litpool-str-1.c
@@ -0,0 +1,22 @@
+/* Make sure strings are recognized as being accessible through larl.
+ This requires the symbol ref alignment properly propagated to
+ encode_section_info. */
+
+/* { dg-do compile } */
+/* { dg-options "-march=z900 -O2 -fpic" } */
+
+
+extern void foo(const char*, const char*, const char*);
+
+void bar(int i)
+{
+ const char t1[10] = "test";
+ const char t2[10] = "test2";
+ const char t3[2][10] = {
+ "foofoofoo",
+ "barbarbar",
+ };
+ foo(t1, t2, t3[i]);
+}
+
+/* { dg-final { scan-assembler-not "GOTOFF" } } */
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 5b15847..68a7ba2 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -3296,6 +3296,10 @@ build_constant_desc (tree exp)
set_mem_attributes (rtl, exp, 1);
set_mem_alias_set (rtl, 0);
+ /* Putting EXP into the literal pool might have imposed a larger
+ alignment which should be visible in the RTX as well. */
+ set_mem_align (rtl, DECL_ALIGN (decl));
+
/* We cannot share RTX'es in pool entries.
Mark this piece of RTL as required for unsharing. */
RTX_FLAG (rtl, used) = 1;
--
2.9.1
