tgsi-to-nir: initialize NIR_DEBUG envvar

This envvar is initialized when creating a NIR shader, but it needs to
be used before. So initialize it here.

v2 (Juan):
 - Use static variable for first initialization.

Fixes: f77ccdfb4a ("nir: add NIR_DEBUG envvar")
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14057>

src/compiler/nir/nir.c

@@ -39,7 +39,7 @@
 #include "main/menums.h" /* BITFIELD64_MASK */
 
 #ifndef NDEBUG
-uint32_t nir_debug = ~0;
+uint32_t nir_debug = 0;
 bool nir_debug_print_shader[MESA_SHADER_KERNEL + 1] = { 0 };
 
 static const struct debug_named_value nir_debug_control[] = {
@@ -90,10 +90,12 @@ static const struct debug_named_value nir_debug_control[] = {
 
 DEBUG_GET_ONCE_FLAGS_OPTION(nir_debug, "NIR_DEBUG", nir_debug_control, 0)
 
-static void
+void
 nir_process_debug_variable(void)
 {
-   if (unlikely(nir_debug == ~0)) {
+   static bool first = true;
+   if (unlikely(first)) {
+      first = false;
       nir_debug = debug_get_option_nir_debug();
       nir_debug_print_shader[MESA_SHADER_VERTEX]       = NIR_DEBUG(PRINT_VS);
       nir_debug_print_shader[MESA_SHADER_TESS_CTRL]    = NIR_DEBUG(PRINT_TCS);

src/compiler/nir/nir.h

@@ -124,6 +124,9 @@ nir_num_components_valid(unsigned num_components)
            num_components == 16;
 }
 
+void
+nir_process_debug_variable(void);
+
 bool nir_component_mask_can_reinterpret(nir_component_mask_t mask,
                                         unsigned old_bit_size,
                                         unsigned new_bit_size);

src/gallium/auxiliary/nir/tgsi_to_nir.c

@@ -2580,6 +2580,10 @@ tgsi_to_nir(const void *tgsi_tokens,
    if (s)
       return s;
 
+#ifndef NDEBUG
+   nir_process_debug_variable();
+#endif
+
    if (NIR_DEBUG(TGSI)) {
       fprintf(stderr, "TGSI before translation to NIR:\n");
       tgsi_dump(tgsi_tokens, 0);