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* [gcc r13-4707] btf: add 'extern' linkage for variables [PR106773]
@ 2022-12-14 18:25 David Faust
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From: David Faust @ 2022-12-14 18:25 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:2bce22e88e1c8486a0f2d42311506a8d3da20fb7
commit r13-4707-g2bce22e88e1c8486a0f2d42311506a8d3da20fb7
Author: David Faust <david.faust@oracle.com>
Date: Wed Dec 7 11:44:28 2022 -0800
btf: add 'extern' linkage for variables [PR106773]
Add support for the 'extern' linkage value for BTF_KIND_VAR records,
which is used for variables declared as extern in the source file.
This also fixes a bug with BTF generation for extern variables which
have both a non-defining declaration and a defining declaration in the
same CU.
PR target/106773
gcc/
* btfout.cc (btf_collect_datasec): Mark extern variables as such.
(btf_dvd_emit_preprocess_cb): Skip non-defining extern variable decl
if there is a defining decl for the same variable.
(btf_asm_varent): Accomodate 'extern' linkage.
gcc/testsuite/
* gcc.dg/debug/btf/btf-variables-4.c: New test.
* gcc.dg/debug/btf/btf-variables-5.c: New test.
include/
* btf.h (enum btf_var_linkage): New.
(struct btf_var): Update comment to note 'extern' linkage.
Diff:
---
gcc/btfout.cc | 11 ++++++++++-
gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c | 24 ++++++++++++++++++++++++
gcc/testsuite/gcc.dg/debug/btf/btf-variables-5.c | 19 +++++++++++++++++++
include/btf.h | 11 ++++++++++-
4 files changed, 63 insertions(+), 2 deletions(-)
diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index aef9fd70a28..677e8324424 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -314,6 +314,9 @@ btf_collect_datasec (ctf_container_ref ctfc)
continue;
const char *section_name = node->get_section ();
+ /* Mark extern variables. */
+ if (DECL_EXTERNAL (node->decl))
+ dvd->dvd_visibility = BTF_VAR_GLOBAL_EXTERN;
if (section_name == NULL)
{
@@ -431,6 +434,12 @@ btf_dvd_emit_preprocess_cb (ctf_dvdef_ref *slot, ctf_container_ref arg_ctfc)
{
ctf_dvdef_ref var = (ctf_dvdef_ref) * slot;
+ /* If this is an extern variable declaration with a defining declaration
+ later, skip it so that only the defining declaration is emitted.
+ This is the same case, fix and reasoning as in CTF; see PR105089. */
+ if (ctf_dvd_ignore_lookup (arg_ctfc, var->dvd_key))
+ return 1;
+
/* Do not add variables which refer to unsupported types. */
if (btf_removed_type_p (var->dvd_type))
return 1;
@@ -676,7 +685,7 @@ btf_asm_varent (ctf_dvdef_ref var)
dw2_asm_output_data (4, var->dvd_name_offset, "btv_name");
dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_VAR, 0, 0), "btv_info");
dw2_asm_output_data (4, get_btf_id (var->dvd_type), "btv_type");
- dw2_asm_output_data (4, (var->dvd_visibility ? 1 : 0), "btv_linkage");
+ dw2_asm_output_data (4, var->dvd_visibility, "btv_linkage");
}
/* Asm'out a member description following a BTF_KIND_STRUCT or
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
new file mode 100644
index 00000000000..d77600bae1c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
@@ -0,0 +1,24 @@
+/* Test BTF generation for extern variables. */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -gbtf -dA" } */
+
+/* Expect 4 variables. */
+/* { dg-final { scan-assembler-times "\[\t \]0xe000000\[\t \]+\[^\n\]*btv_info" 4 } } */
+
+/* 2 extern, 1 global, 1 static. */
+/* { dg-final { scan-assembler-times "\[\t \]0\[\t \]+\[^\n\]*btv_linkage" 1 } } */
+/* { dg-final { scan-assembler-times "\[\t \]0x1\[\t \]+\[^\n\]*btv_linkage" 1 } } */
+/* { dg-final { scan-assembler-times "\[\t \]0x2\[\t \]+\[^\n\]*btv_linkage" 2 } } */
+
+extern int a;
+extern const int b;
+int c;
+static const int d = 5;
+
+int foo (int x)
+{
+ c = a + b + x;
+
+ return c + d;
+}
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-variables-5.c b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-5.c
new file mode 100644
index 00000000000..8aae76cacab
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-5.c
@@ -0,0 +1,19 @@
+/* Test BTF generation for extern variable with both non-defining and
+ defining declarations.
+
+ In this case, only a single variable record should be emitted,
+ with 'global' linkage. However two array types will be generated. */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -gbtf -dA" } */
+
+/* Expect 1 variable with global (1) linkage. */
+/* { dg-final { scan-assembler-times "\[\t \]0xe000000\[\t \]+\[^\n\]*btv_info" 1 } } */
+/* { dg-final { scan-assembler-times "\[\t \]0x1\[\t \]+\[^\n\]*btv_linkage" 1 } } */
+
+/* Expect 2 array types, one of which is unsized. */
+/* { dg-final { scan-assembler-times "\[\t \]0x4\[\t \]+\[^\n\]*bta_nelems" 1 } } */
+/* { dg-final { scan-assembler-times "\[\t \]0\[\t \]+\[^\n\]*bta_nelems" 1 } } */
+
+extern const char FOO[];
+const char FOO[] = "foo";
diff --git a/include/btf.h b/include/btf.h
index eba67f9d599..da621353aa1 100644
--- a/include/btf.h
+++ b/include/btf.h
@@ -178,11 +178,20 @@ struct btf_param
uint32_t type; /* Type of parameter. */
};
+/* BTF_KIND_VAR records encode linkage information in a single
+ trailing struct btf_var. These are the supported values. */
+enum btf_var_linkage
+{
+ BTF_VAR_STATIC = 0,
+ BTF_VAR_GLOBAL_ALLOCATED = 1,
+ BTF_VAR_GLOBAL_EXTERN = 2,
+};
+
/* BTF_KIND_VAR is followed by a single struct btf_var, which describes
information about the variable. */
struct btf_var
{
- uint32_t linkage; /* Currently only 0=static or 1=global. */
+ uint32_t linkage; /* 0=static, 1=global, 2=extern. */
};
/* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
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