Moving definitions to use dedicated scratch register.

code/duffle/gte.atom.c

@@ -372,7 +372,7 @@ atom_info(atom_bind(Binds_gte_cross_v3s4)) MipsAtom_Proc_(aa, {
 	load_word(r.y.src_a,  R_TapePtr, O_(Binds_gte_cross_v3s4,src_a)),
 	load_word(r.z.src_b,  R_TapePtr, O_(Binds_gte_cross_v3s4,src_b)),
 	load_word(r.x.out,    R_TapePtr, O_(Binds_gte_cross_v3s4,out)),
-	LdSlot_ add_ui_self(R_TapePtr, S_(Binds_gte_cross_v3s4)),
+	LdSlot_ add_ui_self(  R_TapePtr, S_(Binds_gte_cross_v3s4)),
 
 	mac_load_v3s4(r.a, r.y.src_a, 0), LdSlot_
 	mac_load_v3s4(r.b, r.z.src_b, 0), LdSlot_

code/duffle/lottes_tape.h

@@ -383,8 +383,8 @@ FI_ Reg regfile__alloc_helper(A2_U2 file, Reg r_id) {
  * any of them while R0, R1, R26-R31 remain reserved. */
 I_ Reg regfile_alloc(RegFile_R rf) {
 	Reg allocated = 0;
-	for index_iter(U4, idx, 0, <, Array_len(regfile_alloc_order)) {
+	for index_iter(U4, r_id, R_V0, <, R_T9) {
-		allocated = regfile__alloc_helper(rf->GPR, idx);
+		allocated = regfile__alloc_helper(rf->GPR, r_id);
 		Jmp_nZero_(allocated,resolved);
 	}
 	assert(allocated != 0);

code/hello_camera/hello_camera.atom.c

@@ -111,39 +111,33 @@ typedef AtomBundle_(resolve_look_at) { MipsAtom
 	*pop_mv_trans;
 };
 
-enum {
+typedef Struct_(ResolveLookAtScratch) {
-	// TODO(Ed): We can resolve scratch at anytime its fixed to a specific address.
+	V3_S4 fwd;
-	R_ResolveScratch = R_T4 atom_reg atom_type(U4*),
+	V3_S4 uz;
-#define R_ResolveScratch_Code R_T4_Code
+	V3_S4 right;
+	V3_S4 ux;
+	V3_S4 up;
+	V3_S4 uy;
+	P3_S4 eye;
+	P3_S4 target;
+	V3_S4 up_in;
 };
+
+/* Binds_ResolveLookAtSub — what the C side pushes onto the tape before input_and_sub.
+ * The scratchpad base is no longer pushed because R_ScratchBase (= R_SP) is a tape carrier
+ * preserved across atoms; the atom body reads 0x1F800000 directly from R_SP. */
 typedef Struct_(Binds_ResolveLookAt) {
 	MT3_S2S4* look_at;
 	P3_S4*    eye;
 	P3_S4*    target;
 	V3_S4*    up_in;
 };
-
-/* ─── ResolveLookAtScratch — offset schema for the resolve_look_at bundle's */
-typedef Struct_(ResolveLookAtScratch) {
-	V3_S4 fwd;       /* offset  +0  (16 bytes — 4 S4 fields incl. internal pad) */
-	V3_S4 uz;        /* offset +16 (16 bytes) */
-	V3_S4 right;     /* offset +32 (16 bytes) */
-	V3_S4 ux;        /* offset +48 (16 bytes) */
-	V3_S4 up;        /* offset +64 (16 bytes) */
-	V3_S4 uy;        /* offset +80 (16 bytes) */
-	P3_S4 eye;       /* offset +96 (16 bytes; storage alias of V3_S4) */
-	P3_S4 target;    /* offset +112 (16 bytes; storage alias of V3_S4) */
-	V3_S4 up_in;     /* offset +128 (16 bytes) */
-};
-
 typedef Struct_(Binds_ResolveLookAtSub) {
 	P3_S4* target;
 	P3_S4* eye;
 	V3_S4* up_in;
-	ResolveLookAtScratch* scratchpad;
 };
 typedef Struct_(RegUse_resolve_look_at_input_and_sub) {
-	Reg scratch;
 	Reg target; Reg eye; Reg up_in;
 	Reg t0; Reg t1; Reg t2; Reg t3; Reg t4;
 };
@@ -153,16 +147,15 @@ atom_info(atom_bind(Binds_ResolveLookAtSub)) MipsAtom_Proc_(aa, {
 	load_word(r.target, R_TapePtr, O_(Binds_ResolveLookAtSub,target)),
 	load_word(r.eye,    R_TapePtr, O_(Binds_ResolveLookAtSub,eye)),
 	load_word(r.up_in,  R_TapePtr, O_(Binds_ResolveLookAtSub,up_in)),
-	load_word(r.scratch, R_TapePtr, O_(Binds_ResolveLookAtSub,scratchpad)),
+	LdSlot_ add_ui_self(R_TapePtr, S_(Binds_ResolveLookAtSub)),
-	LdSlot_ add_ui_self( R_TapePtr, S_(Binds_ResolveLookAtSub)),
 
-	/* Stage up_in.x/y/z into the scratchpad. */
+	/* Stage up_in.x/y/z into the scratchpad. R_ScratchBase = R_SP = 0x1F800000. */
 	mac_load_word_v3( r.t0, r.t1, r.t2, r.up_in,   0), LdSlot_
-	mac_store_word_v3(r.t0, r.t1, r.t2, r.scratch, O_(ResolveLookAtScratch,up_in)),
+	mac_store_word_v3(r.t0, r.t1, r.t2, R_ScratchBase, O_(ResolveLookAtScratch,up_in)),
 
 	// Stage eye.x/y/z into the scratchpad (atom 6 reads these for the translation column).
 	mac_load_word_v3( r.t0, r.t1, r.t2, r.eye,      0), LdSlot_
-	mac_store_word_v3(r.t0, r.t1, r.t2, r.scratch, O_(ResolveLookAtScratch,eye)),
+	mac_store_word_v3(r.t0, r.t1, r.t2, R_ScratchBase, O_(ResolveLookAtScratch,eye)),
 
 	/* Compute fwd = target - eye. */
 	// mac_load_p3s4(t3, R_AT, t4, r.eye,    0),
@@ -170,7 +163,7 @@ atom_info(atom_bind(Binds_ResolveLookAtSub)) MipsAtom_Proc_(aa, {
 	mac_sub_s_v3_self(
 		r.t3, R_AT, r.t4,
 		r.t0, r.t1, r.t2),
-	mac_store_word_v3(r.t3, R_AT, r.t4, r.scratch, O_(ResolveLookAtScratch,fwd)),
+	mac_store_word_v3(r.t3, R_AT, r.t4, R_ScratchBase, O_(ResolveLookAtScratch,fwd)),
 
 	mac_yield()
 })
@@ -180,8 +173,6 @@ typedef Struct_(Binds_ResolveLookAtPopMvTrans) {
 	U4 look_at;  /* MT3_S2S4* — destination matrix address */
 };
 typedef Struct_(RegUse_resolve_look_at__pop_mv_trans) {
-	Reg         scratch;          /* loaded via load_word_imm below — can't rely on
-	                              * R_T4 surviving across the tape_run boundary */
 	Reg         look_at;
 	Reg_(V3_S4) row;             /* populate phase: load ux/uy/uz */
 	union { Reg ux, v_x; } t6;   /* populate addr (canonical) → matrix_vector v_x */
@@ -236,17 +227,13 @@ internal MipsAtom* resolve_look_at__pop_mv_trans(AtomArena_R aa,
 	load_word(r.look_at, R_TapePtr, O_(Binds_ResolveLookAtPopMvTrans,look_at)),
 	LdSlot_ add_ui_self(R_TapePtr, S_(Binds_ResolveLookAtPopMvTrans)),
 
-	/* Load scratch base via immediate (Scratchpad_Loc = 0x1F800000). We can't rely on
+	/* --- Scratch addresses for ux/uy/uz/eye (populate phase; t6/t7/t8 alias ux/uy/uz).
-	 * R_T4 (= R_ResolveScratch) surviving across the tape_run boundary — the compiler
+	 * R_ScratchBase (= R_SP) holds 0x1F800000; no per-atom bake is required because
-	 * treats it as clobberable per the tape_run asm_clobber list. Baking the scratch
+	 * R_SP is a tape carrier preserved across atoms. --- */
-	 * address via load_word_imm is robust. */
+	add_si(r.t6.ux, R_ScratchBase, O_(ResolveLookAtScratch, ux)),  LdSlot_
-	mac_load_word_imm(r.scratch, Scratchpad_Loc),
+	add_si(r.t7.uy, R_ScratchBase, O_(ResolveLookAtScratch, uy)),
-
+	add_si(r.t8.uz, R_ScratchBase, O_(ResolveLookAtScratch, uz)),
-	/* --- Scratch addresses for ux/uy/uz/eye (populate phase; t6/t7/t8 alias ux/uy/uz) --- */
+	add_si(r.eye,   R_ScratchBase, O_(ResolveLookAtScratch, eye)),
-	add_si(r.t6.ux, r.scratch, O_(ResolveLookAtScratch, ux)),  LdSlot_
-	add_si(r.t7.uy, r.scratch, O_(ResolveLookAtScratch, uy)),
-	add_si(r.t8.uz, r.scratch, O_(ResolveLookAtScratch, uz)),
-	add_si(r.eye,   r.scratch, O_(ResolveLookAtScratch, eye)),
 
 	/* --- POPULATE phase: write look_at->m[][] from ux/uy/uz as packed S2 --- */
 	mac_load_v3s4(r.row, r.t6.ux, 0), LdSlot_ mac_store_v3s2(r.row, r.look_at, O_(MT3_S2S4, m[0])),

code/hello_camera/hello_camera.c

@@ -158,6 +158,7 @@ internal void compile_init_atoms(void) {
 			.norm        = ralloc(),
 			.shift       = ralloc(),
 			.src_x       = ralloc(),
+			// .shift_count = ralloc(),    /* dedicated slot for stage-3 → stage-4 shift count */
 			.t3          = ralloc(),
 			.t4          = ralloc(),
 			.t5          = ralloc(),
@@ -173,14 +174,14 @@ internal void compile_resolve_look_at(void) {
 	AtomArena ab = atomarena_make(slice_ut_arr(smem.resolve_look_at_mem));
 	AtomBundle_resolve_look_at_R bundle = C_(void*, smem.resolve_look_at_bundle);
 
-	U4 pin_mask = regfile_abi_mask | (1 << R_ResolveScratch);
+	/* R_ScratchBase (= R_SP) is a tape carrier preserved across atoms; no carrier
-	RegFile rf  = regfile(pin_mask);
+	 * pin is needed in the regfile. The standard 24-register pool is sufficient. */
+	RegFile rf = regfile(regfile_abi_mask);
 #define ralloc() regfile_alloc(& rf)
 #define ralloc_v3() { ralloc(), ralloc(), ralloc() }
 
 	bundle->input_and_sub = AtomBundleEntry_(resolve_look_at, input_and_sub)(& ab,
 		RegUse_(resolve_look_at_input_and_sub) {
-			.scratch = R_ResolveScratch,
 			.target  = ralloc(),
 			.eye     = ralloc(),
 			.up_in   = ralloc(),
@@ -190,7 +191,7 @@ internal void compile_resolve_look_at(void) {
 			.t3      = ralloc(),
 			.t4      = ralloc(),
 		});
-	regfile_reset_to_mask(& rf, pin_mask);
+	regfile_reset(& rf);
 
 	bundle->normalize_fwd_uz   = smem.normalize_v3s4;
 	bundle->cross_to_right     = smem.gte_cross_v3s4;
@@ -200,7 +201,6 @@ internal void compile_resolve_look_at(void) {
 
 	bundle->pop_mv_trans = resolve_look_at__pop_mv_trans(& ab,
 		RegUse_(resolve_look_at__pop_mv_trans){
-			.scratch = R_ResolveScratch,
 			.look_at = ralloc(),
 			.eye     = ralloc(),
 			.row     = ralloc_v3(),
@@ -229,7 +229,6 @@ I_ void resolve_look_at(TapeBuilder_R tb
 		tb_data(tb, u4_(target));
 		tb_data(tb, u4_(eye));
 		tb_data(tb, u4_(up_in));
-		tb_data(tb, u4_(smem.scratchpad));
 	}
 	tb_emit(tb, bundle->normalize_fwd_uz); {
 		tb_data(tb, u4_(O_(ResolveLookAtScratch, fwd) | (O_(ResolveLookAtScratch, uz) << 16)));

scripts/passes/components.lua

@@ -130,6 +130,60 @@ local function extract_arg_names(args_str)
 	for _, tok in ipairs(tokens) do
 		local trimmed = duffle.trim(tok)
 		if trimmed ~= "" then
+			-- Strip trailing block comment (/* ... */) from the token, if present.
+			-- split_top_level_commas only skips block comments at TOP LEVEL (between commas),
+			-- not block comments embedded WITHIN a token between a parameter and a trailing comma.
+			-- Without this strip, the identifier-walk below stops at the `/` of `*/` and returns
+			-- the wrong name (or nothing). See `test_extract_arg_names_handles_trailing_block_comments`.
+			local trimmed_end = #trimmed
+			if trimmed_end >= 2 and trimmed:sub(trimmed_end - 1, trimmed_end) == "*/" then
+				-- Find the matching `/*` that opens the trailing comment.
+				-- Walk back from the `*/` looking for `/*` (whitespace + `/*`).
+				local close_pos = trimmed_end - 1   -- position of the second-to-last char
+				-- Walk back: skip trailing whitespace, then look for the `/*` opener.
+				while close_pos > 1 do
+					local ch = trimmed:sub(close_pos, close_pos)
+					if ch == " " or ch == "\t" or ch == "\n" or ch == "\r" then
+						close_pos = close_pos - 1
+					else
+						break
+					end
+				end
+				-- Now scan back from close_pos for the `/*` opener (slashes are at close_pos-1 and close_pos-2).
+				local opener_pos = nil
+				local scan = close_pos - 3
+				while scan >= 1 do
+					if trimmed:sub(scan, scan + 1) == "/*" then
+						opener_pos = scan
+						break
+					end
+					scan = scan - 1
+				end
+				if opener_pos then
+					-- Truncate everything from opener_pos onwards.
+					trimmed = duffle.trim(trimmed:sub(1, opener_pos - 1))
+				end
+			end
+			if trimmed == "" then goto continue end
+			-- Strip trailing array suffix `[N]` if present.
+			-- Example: `Reg r_data[4]` → identifier is `r_data`, not `4`.
+			trimmed_end = #trimmed
+			if trimmed_end >= 4 and trimmed:sub(trimmed_end, trimmed_end) == "]" then
+				-- Walk back: skip digits, expect `[`.
+				local bracket_pos = trimmed_end - 1
+				while bracket_pos > 1 do
+					local ch = trimmed:sub(bracket_pos, bracket_pos)
+					if ch >= "0" and ch <= "9" then
+						bracket_pos = bracket_pos - 1
+					else
+						break
+					end
+				end
+				if bracket_pos >= 1 and trimmed:sub(bracket_pos, bracket_pos) == "[" then
+					trimmed = duffle.trim(trimmed:sub(1, bracket_pos - 1))
+				end
+			end
+			if trimmed == "" then goto continue end
 			-- Find the identifier at the end: walk back over trailers (whitespace + `*` + `[]`),
 			-- then walk back over the identifier chars (alnum + `_`).
 			local ident_end = #trimmed
@@ -153,6 +207,7 @@ local function extract_arg_names(args_str)
 			ident_start = ident_start + 1
 			local name = trimmed:sub(ident_start, ident_end)
 			if name ~= "" then names[#names + 1] = name end
+			::continue::
 		end
 	end
 	if #names == 0 then return nil end