[PTX] Add weak support

[PTX] Add weak support

[Nathan Sidwell]

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I've committed this patch to trunk, which adds weak symbol support to PTX.  PTX 
supports weak definitions but not weak declarations, so some of the tests need 
explicitly skipping, however the overall change is for the better.

I did discover a bug in the PTX JIT, in that it resolved weak definitions too 
early, and have reported that to Nvidia. This affected gcc.dg/special/weak-2.c, 
which is thus skipped.

nathan

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2015-11-19  Nathan Sidwell  <nathan@acm.org>

	gcc/
	* config/nvptx/nvptx.h (SUPPORTS_WEAK): Define.
	* config/nvptx/nvptx.c (nvptx_write_function_decl): Support
	DECL_WEAK.
	(nvptx_declare_objec_name): Likewise.

	gcc/testsuite/
	* lib/target-supports.exp (check_weak_available): Add nvptx-*-*.
	* gcc.dg/attr-weakref-1.c: Skip for nvptx-*-*
	* gcc.dg/special/weak-2.c: Likewise.
	* gcc.dg/weak/weak-12.c: Likewise.
	* gcc.dg/weak/weak-15.c: Likewise.
	* gcc.dg/weak/weak-16.c: Likewise.
	* gcc.dg/weak/weak-1.c: Likewise.
	* gcc.dg/weak/weak-2.c: Likewise.
	* gcc.dg/weak/weak-4.c: Likewise.
	* gcc.dg/torture/pr53922.c: Likewise.
	* gcc.dg/torture/pr60092.c: Likewise.

Index: config/nvptx/nvptx.c
===================================================================
--- config/nvptx/nvptx.c	(revision 230554)
+++ config/nvptx/nvptx.c	(working copy)
@@ -379,7 +379,7 @@ nvptx_write_function_decl (std::stringst
   if (DECL_EXTERNAL (decl))
     s << ".extern ";
   else if (TREE_PUBLIC (decl))
-    s << ".visible ";
+    s << (DECL_WEAK (decl) ? ".weak " : ".visible ");
 
   if (kernel)
     s << ".entry ";
@@ -1780,8 +1780,9 @@ nvptx_declare_object_name (FILE *file, c
       size = tree_to_uhwi (DECL_SIZE_UNIT (decl));
       const char *section = nvptx_section_for_decl (decl);
       fprintf (file, "\t%s%s .align %d .u%d ",
-	       TREE_PUBLIC (decl) ? " .visible" : "", section,
-	       DECL_ALIGN (decl) / BITS_PER_UNIT,
+	       !TREE_PUBLIC (decl) ? ""
+	       : DECL_WEAK (decl) ? ".weak" : ".visible",
+	       section, DECL_ALIGN (decl) / BITS_PER_UNIT,
 	       decl_chunk_size * BITS_PER_UNIT);
       assemble_name (file, name);
       if (size > 0)
Index: config/nvptx/nvptx.h
===================================================================
--- config/nvptx/nvptx.h	(revision 230554)
+++ config/nvptx/nvptx.h	(working copy)
@@ -349,6 +349,7 @@ struct GTY(()) machine_function
 #define CTZ_DEFINED_VALUE_AT_ZERO(MODE, VALUE) \
   ((VALUE) = GET_MODE_BITSIZE ((MODE)), 2)
 
+#define SUPPORTS_WEAK 1
 #define NO_DOT_IN_LABEL
 #define ASM_COMMENT_START "//"
 
Index: testsuite/lib/target-supports.exp
===================================================================
--- testsuite/lib/target-supports.exp	(revision 230554)
+++ testsuite/lib/target-supports.exp	(working copy)
@@ -292,6 +292,12 @@ proc check_weak_available { } {
 	return 0
     }
 
+    # nvptx (nearly) supports it
+
+    if { [istarget nvptx-*-*] } {
+	return 1
+    }
+
     # ELF and ECOFF support it. a.out does with gas/gld but may also with
     # other linkers, so we should try it
 
Index: testsuite/gcc.dg/attr-weakref-1.c
===================================================================
--- testsuite/gcc.dg/attr-weakref-1.c	(revision 230554)
+++ testsuite/gcc.dg/attr-weakref-1.c	(working copy)
@@ -1,10 +1,12 @@
 // { dg-do run }
 // { dg-require-weak "" }
 // On darwin, we use attr-weakref-1-darwin.c.
+
 // This test requires support for undefined weak symbols.  This support
-// is not available on hppa*-*-hpux*.  The test is skipped rather than
+// is not available on the following targets.  The test is skipped rather than
 // xfailed to suppress the warning that would otherwise arise.
-// { dg-skip-if "" { "hppa*-*-hpux*" "*-*-aix*" } "*" { "" } }
+// { dg-skip-if "" { "hppa*-*-hpux*" "*-*-aix*" "nvptx-*-*" } "*" { "" } }
+
 // For kernel modules and static RTPs, the loader treats undefined weak
 // symbols in the same way as undefined strong symbols.  The test
 // therefore fails to load, so skip it.
Index: testsuite/gcc.dg/special/weak-2.c
===================================================================
--- testsuite/gcc.dg/special/weak-2.c	(revision 230554)
+++ testsuite/gcc.dg/special/weak-2.c	(working copy)
@@ -2,6 +2,10 @@
 /* { dg-require-weak "" } */
 /* { dg-additional-sources "weak-2a.c weak-2b.c" } */
 
+/* NVPTX's implementation of weak is broken when a strong symbol is in
+   a later object file than the weak definition.   */
+/* { dg-skip-if "" { "nvptx-*-*" } "*" { "" } } */
+
 #include <stdlib.h>
 
 extern int foo(void);
Index: testsuite/gcc.dg/weak/weak-12.c
===================================================================
--- testsuite/gcc.dg/weak/weak-12.c	(revision 230554)
+++ testsuite/gcc.dg/weak/weak-12.c	(working copy)
@@ -2,6 +2,8 @@
 /* { dg-do compile } */
 /* { dg-require-weak "" } */
 /* { dg-options "" } */
+/* NVPTX's weak is applied to the definition,  not declaration.  */
+/* { dg-skip-if "" { nvptx-*-* } { "*" } { "" } } */
 
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?foo" } } */
 
Index: testsuite/gcc.dg/weak/weak-15.c
===================================================================
--- testsuite/gcc.dg/weak/weak-15.c	(revision 230554)
+++ testsuite/gcc.dg/weak/weak-15.c	(working copy)
@@ -2,6 +2,8 @@
 /* { dg-require-weak "" } */
 /* { dg-options "-fno-common" } */
 /* { dg-skip-if "" { x86_64-*-mingw* } { "*" } { "" } } */
+/* NVPTX's weak is applied to the definition,  not declaration.  */
+/* { dg-skip-if "" { nvptx-*-* } { "*" } { "" } } */
 
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?a" } } */
 /* { dg-final { scan-assembler-not "weak\[^ \t\]*\[ \t\]_?b" } } */
Index: testsuite/gcc.dg/weak/weak-16.c
===================================================================
--- testsuite/gcc.dg/weak/weak-16.c	(revision 230554)
+++ testsuite/gcc.dg/weak/weak-16.c	(working copy)
@@ -5,6 +5,8 @@
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?kallsyms_token_index" } } */
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?kallsyms_token_table" } } */
 /* { dg-skip-if "" { x86_64-*-mingw* } { "*" } { "" } } */
+/* NVPTX's weak is applied to the definition,  not declaration.  */
+/* { dg-skip-if "" { nvptx-*-* } { "*" } { "" } } */
 
 extern int kallsyms_token_index[] __attribute__((weak));
 extern int kallsyms_token_table[] __attribute__((weak));
Index: testsuite/gcc.dg/weak/weak-1.c
===================================================================
--- testsuite/gcc.dg/weak/weak-1.c	(revision 230554)
+++ testsuite/gcc.dg/weak/weak-1.c	(working copy)
@@ -2,6 +2,8 @@
 /* { dg-require-weak "" } */
 /* { dg-options "-fno-common" } */
 /* { dg-skip-if "" { *-*-mingw* } { "*" } { "" } } */
+/* NVPTX's definition of weak looks different to normal.  */
+/* { dg-skip-if "" { nvptx-*-* } { "*" } { "" } } */
 
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?a" } } */
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?b" } } */
Index: testsuite/gcc.dg/weak/weak-2.c
===================================================================
--- testsuite/gcc.dg/weak/weak-2.c	(revision 230554)
+++ testsuite/gcc.dg/weak/weak-2.c	(working copy)
@@ -2,6 +2,8 @@
 /* { dg-require-weak "" } */
 /* { dg-options "-fno-common" } */
 /* { dg-skip-if "" { x86_64-*-mingw* } { "*" } { "" } } */
+/* NVPTX's definition of weak looks different to normal.  */
+/* { dg-skip-if "" { nvptx-*-* } { "*" } { "" } } */
 
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?ffoo1a" } } */
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?ffoo1b" } } */
Index: testsuite/gcc.dg/weak/weak-4.c
===================================================================
--- testsuite/gcc.dg/weak/weak-4.c	(revision 230554)
+++ testsuite/gcc.dg/weak/weak-4.c	(working copy)
@@ -2,6 +2,8 @@
 /* { dg-require-weak "" } */
 /* { dg-options "-fno-common" } */
 /* { dg-skip-if "" { x86_64-*-mingw* } { "*" } { "" } } */
+/* NVPTX's definition of weak looks different to normal.  */
+/* { dg-skip-if "" { nvptx-*-* } { "*" } { "" } } */
 
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?vfoo1a" } } */
 /* { dg-final { scan-assembler "weak\[^ \t\]*\[ \t\]_?vfoo1b" } } */
Index: testsuite/gcc.dg/torture/pr53922.c
===================================================================
--- testsuite/gcc.dg/torture/pr53922.c	(revision 230554)
+++ testsuite/gcc.dg/torture/pr53922.c	(working copy)
@@ -3,6 +3,7 @@
 /* { dg-skip-if "No undefined" { *-*-mingw* } { "*" } { "" } } */
 /* { dg-skip-if "No undefined weak" { *-*-aix* } { "*" } { "" } } */
 /* { dg-skip-if "No undefined weak" { hppa*-*-hpux* && { ! lp64 } } { "*" } { "" } } */
+/* { dg-skip-if "No undefined weak" { nvptx-*-* } { "*" } { "" } } */
 /* { dg-options "-Wl,-undefined,dynamic_lookup" { target *-*-darwin* } } */
 /* { dg-additional-options "-Wl,-flat_namespace" { target *-*-darwin[89]* } } */
 
Index: testsuite/gcc.dg/torture/pr60092.c
===================================================================
--- testsuite/gcc.dg/torture/pr60092.c	(revision 230554)
+++ testsuite/gcc.dg/torture/pr60092.c	(working copy)
@@ -1,6 +1,7 @@
 /* { dg-do run } */
 /* { dg-require-weak "" } */
 /* { dg-skip-if "No undefined weak" { hppa*-*-hpux* && { ! lp64 } } } */
+/* { dg-skip-if "No undefined weak" { nvptx-*-* } { "*" } { "" } } */
 /* { dg-additional-options "-Wl,-undefined,dynamic_lookup" { target *-*-darwin* } } */
 /* { dg-additional-options "-Wl,-flat_namespace" { target *-*-darwin[89]* } } */
 /* { dg-xfail-run-if "posix_memalign modifies first arg on error" { *-*-solaris2.11* } { "-O0" } } */