nvptx: Sanity-check 'init_frag' state

The 'init_frag' machinery is used by 'nvptx_assemble_integer' (via
'TARGET_ASM_INTEGER'), 'nvptx_output_skip' (via 'ASM_OUTPUT_SKIP'),
'nvptx_output_ascii' (via 'ASM_OUTPUT_ASCII').  But, it's not obvious that
these are called only when that machinery is active (and in a consistent
state), which it only is in 'nvptx_output_aligned_decl' (via
'ASM_OUTPUT_ALIGNED_DECL_COMMON', or 'ASM_OUTPUT_ALIGNED_DECL_LOCAL'), or in
'nvptx_assemble_undefined_decl' (via 'TARGET_ASM_ASSEMBLE_UNDEFINED_DECL'), or
within a region started by 'nvptx_assemble_decl_begin' (via
'nvptx_asm_declare_constant_name' (via 'TARGET_ASM_DECLARE_CONSTANT_NAME'), or
via 'nvptx_declare_object_name' (via 'ASM_DECLARE_OBJECT_NAME')) and ended by
'nvptx_assemble_decl_end' (via 'TARGET_ASM_DECL_END').

And indeed, in a GCC/nvptx offloading configuration, we then find that
'nvptx_output_skip' (via 'ASM_OUTPUT_SKIP') is getting called in inconsistent
'init_frag' state, in 'gcc/varasm.cc', via 'assemble_zeros', from
'output_object_block', to "Move to the object's offset, padding with zeros".
Supposedly, this didn't cause any damage, but we now handle it explicitly.
(..., and the question remains whether such "padding" etc. shouldn't actually
be attempted for targets like nvptx.)

	gcc/
	* config/nvptx/nvptx.cc (init_frag): New 'bool active' member.
	(output_init_frag, nvptx_assemble_value, nvptx_assemble_integer)
	(nvptx_output_skip, nvptx_assemble_decl_begin)
	(nvptx_assemble_decl_end): Sanity-check its state.

1 files changed, 26 insertions, 0 deletions

diff --git a/gcc/config/nvptx/nvptx.cc b/gcc/config/nvptx/nvptx.cc
index 6f36461..96f258c 100644
--- a/gcc/config/nvptx/nvptx.cc
+++ b/gcc/config/nvptx/nvptx.cc
@@ -2255,6 +2255,7 @@ static struct
 					out.  */
   unsigned size;  /* Fragment size to accumulate.  */
   unsigned offset;  /* Offset within current fragment.  */
+  bool active; /* Whether this machinery is active.  */
   bool started;   /* Whether we've output any initializer.  */
 } init_frag;
 
@@ -2265,6 +2266,8 @@ static struct
 static void
 output_init_frag (rtx sym)
 {
+  gcc_checking_assert (init_frag.active);
+
   fprintf (asm_out_file, init_frag.started ? ", " : " = { ");
   unsigned HOST_WIDE_INT val = init_frag.val;
 
@@ -2296,6 +2299,8 @@ output_init_frag (rtx sym)
 static void
 nvptx_assemble_value (unsigned HOST_WIDE_INT val, unsigned size)
 {
+  gcc_checking_assert (init_frag.active);
+
   bool negative_p
     = val & (HOST_WIDE_INT_1U << (HOST_BITS_PER_WIDE_INT - 1));
 
@@ -2328,6 +2333,8 @@ nvptx_assemble_value (unsigned HOST_WIDE_INT val, unsigned size)
 static bool
 nvptx_assemble_integer (rtx x, unsigned int size, int ARG_UNUSED (aligned_p))
 {
+  gcc_checking_assert (init_frag.active);
+
   HOST_WIDE_INT val = 0;
 
   switch (GET_CODE (x))
@@ -2370,6 +2377,17 @@ nvptx_assemble_integer (rtx x, unsigned int size, int ARG_UNUSED (aligned_p))
 void
 nvptx_output_skip (FILE *, unsigned HOST_WIDE_INT size)
 {
+  gcc_checking_assert (in_section == data_section
+		       || in_section == text_section);
+
+  if (!init_frag.active)
+    /* We're in the 'data_section' or 'text_section', outside of an
+       initializer context ('init_frag').  There's nothing to do here:
+       in PTX, there's no concept of an assembler's "location counter",
+       "current address", "dot symbol" ('.') that might need padding or
+       aligning.  */
+    return;
+
   /* Finish the current fragment, if it's started.  */
   if (init_frag.offset)
     {
@@ -2446,6 +2464,8 @@ nvptx_assemble_decl_begin (FILE *file, const char *name, const char *section,
 			   const_tree type, HOST_WIDE_INT size, unsigned align,
 			   bool undefined = false)
 {
+  gcc_checking_assert (!init_frag.active);
+
   bool atype = (TREE_CODE (type) == ARRAY_TYPE)
     && (TYPE_DOMAIN (type) == NULL_TREE);
 
@@ -2473,6 +2493,8 @@ nvptx_assemble_decl_begin (FILE *file, const char *name, const char *section,
   elt_size |= GET_MODE_SIZE (elt_mode);
   elt_size &= -elt_size; /* Extract LSB set.  */
 
+  init_frag.active = true;
+
   init_frag.size = elt_size;
   /* Avoid undefined shift behavior by using '2'.  */
   init_frag.mask = ((unsigned HOST_WIDE_INT)2
@@ -2504,10 +2526,14 @@ nvptx_assemble_decl_begin (FILE *file, const char *name, const char *section,
 static void
 nvptx_assemble_decl_end (void)
 {
+  gcc_checking_assert (init_frag.active);
+
   if (init_frag.offset)
     /* This can happen with a packed struct with trailing array member.  */
     nvptx_assemble_value (0, init_frag.size - init_frag.offset);
   fprintf (asm_out_file, init_frag.started ? " };\n" : ";\n");
+
+  init_frag.active = false;
 }
 
 /* Output an uninitialized common or file-scope variable.  */