ld_align_segment_start (#373)

* Implement ld_align_segment_start

* docs and changelog

* black

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ### 0.24.3
 
+* New yaml option: `ld_align_segment_start`
+  * Allows specifying an alignment for the start of all the segments.
+  * The alignment can be overriden or disabled per segment too.
 * Add `visibility` attribute to symbols.
   * Allows to specify if a symbol should be declared as `local`, `weak`, etc in the disassembly.
 * `spimdisasm` 1.26.0 or above is now required

docs/Configuration.md

@@ -427,7 +427,6 @@ This behavior can be customized per segment too. See [ld_fill_value](Segments.md
 
 Defaults to 0.
 
-
 ### ld_bss_is_noload
 
 Allows to control if `bss` sections (and derivatived sections) will be put on a `NOLOAD` segment on the generated linker script or not.
@@ -437,6 +436,17 @@ Applies to all `bss` (`sbss`, `common`, `scommon`, etc) sections.
 Defaults to `True`, meaning `bss` sections will be put on `NOLOAD` segments.
 
 
+### ld_align_segment_start
+
+Specify that segments should be aligned before starting them.
+
+This option specifies the desired alignment value, or `null` if no aligment should be imposed on the segment start.
+
+This behavior can be customized per segment too. See [ld_align_segment_start](Segments.md#ld_align_segment_start) on the Segments section.
+
+Defaults to `null`.
+
+
 ### ld_align_segment_vram_end
 
 Allows to toggle aligning the `*_VRAM_END` linker symbol of each segment.

docs/Segments.md

@@ -355,6 +355,14 @@ If not set, then the global configuration is used. See [ld_fill_value](Configura
 
 Defaults to the value of the global option.
 
+### `ld_align_segment_start`
+
+Specify the current segment should be aligned before starting it.
+
+This option specifies the desired alignment value, or `null` if no aligment should be imposed on the segment start.
+
+If not set, then the global configuration is used. See [ld_align_segment_start](Configuration.md#ld_align_segment_start) on the Configuration section.
+
 ### `subalign`
 
 Sub-alignment (in bytes) of sections.

src/splat/segtypes/linker_entry.py

@@ -268,6 +268,12 @@ def add(self, segment: Segment, max_vram_syms: List[Tuple[str, List[Segment]]]):
             any_noload = any_noload or entry.noload
             prev_entry = entry.section_order_type
 
+        if segment.ld_align_segment_start:
+            self._write_symbol(
+                "__romPos", f"ALIGN(__romPos, 0x{segment.ld_align_segment_start:X})"
+            )
+            self._write_symbol(".", f"ALIGN(., 0x{segment.ld_align_segment_start:X})")
+
         seg_rom_start = get_segment_rom_start(seg_name)
         self._write_symbol(seg_rom_start, "__romPos")
 
@@ -305,6 +311,12 @@ def add_legacy(self, segment: Segment, entries: List[LinkerEntry]):
             ):
                 last_seen_sections[entry] = entry.section_order_type
 
+        if segment.ld_align_segment_start:
+            self._write_symbol(
+                "__romPos", f"ALIGN(__romPos, 0x{segment.ld_align_segment_start:X})"
+            )
+            self._write_symbol(".", f"ALIGN(., 0x{segment.ld_align_segment_start:X})")
+
         seg_rom_start = get_segment_rom_start(seg_name)
         self._write_symbol(seg_rom_start, "__romPos")
 
@@ -359,6 +371,12 @@ def add_referenced_partial_segment(
         for sym, segs in max_vram_syms:
             self.write_max_vram_end_sym(sym, segs)
 
+        if segment.ld_align_segment_start:
+            self._write_symbol(
+                "__romPos", f"ALIGN(__romPos, 0x{segment.ld_align_segment_start:X})"
+            )
+            self._write_symbol(".", f"ALIGN(., 0x{segment.ld_align_segment_start:X})")
+
         seg_rom_start = get_segment_rom_start(seg_name)
         self._write_symbol(seg_rom_start, "__romPos")
 

src/splat/segtypes/segment.py

@@ -214,6 +214,12 @@ def parse_ld_fill_value(
             return yaml["ld_fill_value"]
         return default
 
+    @staticmethod
+    def parse_ld_align_segment_start(yaml: Union[dict, list]) -> Optional[int]:
+        if isinstance(yaml, dict) and "ld_align_segment_start" in yaml:
+            return yaml["ld_align_segment_start"]
+        return options.opts.ld_align_segment_start
+
     def __init__(
         self,
         rom_start: Optional[int],
@@ -288,6 +294,10 @@ def __init__(
             yaml, options.opts.ld_fill_value
         )
 
+        self.ld_align_segment_start: Optional[int] = self.parse_ld_align_segment_start(
+            yaml
+        )
+
         # True if this segment was generated based on auto_all_sections
         self.is_auto_all: bool = False
 

src/splat/util/options.py

@@ -131,6 +131,8 @@ class SplatOpts:
     ld_fill_value: Optional[int]
     # Allows to control if `bss` sections (and derivatived sections) will be put on a `NOLOAD` segment on the generated linker script or not.
     ld_bss_is_noload: bool
+    # Aligns the start of the segment to the given value
+    ld_align_segment_start: Optional[int]
     # Allows to toggle aligning the `*_VRAM_END` linker symbol for each segment.
     ld_align_segment_vram_end: bool
     # Allows to toggle aligning the `*_END` linker symbol for each section of each section.
@@ -448,6 +450,9 @@ def parse_endianness() -> Literal["big", "little"]:
         ld_bss_is_noload=p.parse_opt(
             "ld_bss_is_noload", bool, default_ld_bss_is_noload
         ),
+        ld_align_segment_start=p.parse_optional_opt_with_default(
+            "ld_align_segment_start", int, None
+        ),
         ld_align_segment_vram_end=p.parse_opt("ld_align_segment_vram_end", bool, True),
         ld_align_section_vram_end=p.parse_opt("ld_align_section_vram_end", bool, True),
         ld_generate_symbol_per_data_segment=p.parse_opt(