[committed] amdgcn: Pass -mstack-size through to runtime

[Andrew Stubbs]

The -mstack-size option has been marked obsolete in favour of setting an 
environment variable at runtime ("GCN_STACK_SIZE"), but some testcases 
still need the option set or they have stack overflow. I could change 
them to use the envvar, but my testing setup uses remote execute which 
doesn't support that yet, and means I would skip my own tests (not ideal).

This patch causes the testcase to automatically set GCN_STACK_SIZE 
itself, in a hidden constructor (only if it's not already set), and 
therefore bypasses the problem. I'm leaving the documentation saying 
-mstack-size is obsolete because this fix only works for offload tests, 
and it's still not the preferred user solution.

Committed to mainline. I'll backport to OG12 shortly.

Andrewamdgcn: Pass -mstack-size through to runtime

But only for the offload case.

gcc/ChangeLog:

        * config/gcn/mkoffload.cc (gcn_stack_size): New global variable.
        (process_asm): Create a constructor for GCN_STACK_SIZE.
        (main): Parse the -mstack-size option.

diff --git a/gcc/config/gcn/mkoffload.cc b/gcc/config/gcn/mkoffload.cc
index 9c262f974be..9493f89fec3 100644
--- a/gcc/config/gcn/mkoffload.cc
+++ b/gcc/config/gcn/mkoffload.cc
@@ -117,6 +117,8 @@ uint32_t elf_arch = EF_AMDGPU_MACH_AMDGCN_GFX803;  // 
Default GPU architecture.
 uint32_t elf_flags =
     (EF_AMDGPU_FEATURE_XNACK_ANY_V4 | EF_AMDGPU_FEATURE_SRAMECC_ANY_V4);
 
+static int gcn_stack_size = 0;  /* Zero means use default.  */
+
 /* Delete tempfiles.  */
 
 void
@@ -662,6 +664,18 @@ process_asm (FILE *in, FILE *out, FILE *cfile)
     }
   fprintf (cfile, "\n};\n\n");
 
+  /* Set the stack size if the user configured a value.  */
+  if (gcn_stack_size)
+    fprintf (cfile,
+            "static __attribute__((constructor))\n"
+            "void configure_stack_size (void)\n"
+            "{\n"
+            "  const char *val = getenv (\"GCN_STACK_SIZE\");\n"
+            "  if (!val || val[0] == '\\0')\n"
+            "    setenv (\"GCN_STACK_SIZE\", \"%d\", true);\n"
+            "}\n\n",
+            gcn_stack_size);
+
   obstack_free (&fns_os, NULL);
   for (i = 0; i < dims_count; i++)
     free (dims[i].name);
@@ -920,6 +934,10 @@ main (int argc, char **argv)
        elf_arch = EF_AMDGPU_MACH_AMDGCN_GFX908;
       else if (strcmp (argv[i], "-march=gfx90a") == 0)
        elf_arch = EF_AMDGPU_MACH_AMDGCN_GFX90a;
+#define STR "-mstack-size="
+      else if (startswith (argv[i], STR))
+       gcn_stack_size = atoi (argv[i] + strlen (STR));
+#undef STR
     }
 
   if (!(fopenacc ^ fopenmp))