nir/printf: add new helper to printf at a specific pixel.

Debugging with nir_printf_fmt can result in overwhelming information. This
allows us to filter for a pixel we care about.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34737>

src/compiler/nir/nir_builder.h

@@ -2404,6 +2404,8 @@ nir_gen_rect_vertices(nir_builder *b, nir_def *z, nir_def *w);
  */
 void nir_printf_fmt(nir_builder *b, unsigned ptr_bit_size,
                     const char *fmt, ...);
+void nir_printf_fmt_at_px(nir_builder *b, unsigned ptr_bit_size,
+                          unsigned x, unsigned y, const char *fmt, ...);
 
 /* Call a serialized function. This is used internally by vtn_bindgen, it is not
  * intended for end-users of NIR.

src/compiler/nir/nir_lower_printf.c

@@ -329,3 +329,18 @@ nir_printf_fmt(nir_builder *b, unsigned ptr_bit_size, const char *fmt, ...)
    nir_vprintf_fmt(b, ptr_bit_size, fmt, ap);
    va_end(ap);
 }
+
+/* Debug helper to allow us to printf at a single pixel */
+void nir_printf_fmt_at_px(nir_builder *b, unsigned ptr_bit_size, unsigned x_px, unsigned y_px, const char *fmt, ...)
+{
+   va_list ap;
+
+   nir_def *xy_px = nir_f2u32(b,nir_load_frag_coord(b));
+   nir_def *is_at_px = nir_ball_iequal(b, nir_imm_ivec2(b, x_px, y_px), xy_px);
+
+   nir_push_if(b, is_at_px);
+   va_start(ap, fmt);
+   nir_vprintf_fmt(b, ptr_bit_size, fmt, ap);
+   va_end(ap);
+   nir_pop_if(b, NULL);
+}