From 223dbc0619adde456cf5dde7c2c5235c33301b15 Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Sat, 18 Nov 2023 20:17:38 -0600
Subject: rtl/gfx: fix Verilator loop unrolling bug in gfx_pipes

---
 Makefile             | 3 ++-
 rtl/gfx/gfx_pipes.sv | 9 ++-------
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index 01e4c15..f8574ec 100644
--- a/Makefile
+++ b/Makefile
@@ -203,5 +203,6 @@ $(OBJ_DIR)/%.mk: \
 		--Mdir $(dir $@) --top $(word 1,$(subst /, ,$*)) -FI $(ROOT)/$(TB_DIR)/verilator.hpp \
 		$(filter %.sv %.cpp,$(patsubst tb/%,../tb/%,$^)) \
 		$(if $(filter $(TOP),$(word 1,$(subst /, ,$*))),, \
-			--vpi --public-flat-rw -LDFLAGS "$(COCOTB_LDFLAGS) $(LIBPYTHON)" \
+			--vpi --public-flat-rw --unroll-count 128 \
+			-LDFLAGS "$(COCOTB_LDFLAGS) $(LIBPYTHON)" \
 			$(shell $(COCOTB_CONFIG) --share)/lib/verilator/verilator.cpp)
diff --git a/rtl/gfx/gfx_pipes.sv b/rtl/gfx/gfx_pipes.sv
index 390a481..09b1d43 100644
--- a/rtl/gfx/gfx_pipes.sv
+++ b/rtl/gfx/gfx_pipes.sv
@@ -17,13 +17,8 @@ module gfx_pipes
 		if (!stall) begin
 			pipes[0] <= in;
 
-			/* Esto tiene que ir así porque Verilator no soporta <= en for
-			 * loops a las que no logre hacerle unrolling. Nótese que el
-			 * orden de iteración descendiente es necesario porque estamos
-			 * usando un blocking assignment dentro de always_ff.
-			 */
-			for (integer i = DEPTH - 1; i > 0; --i)
-				pipes[i] = pipes[i - 1];
+			for (integer i = 1; i < DEPTH; ++i)
+				pipes[i] <= pipes[i - 1];
 		end
 
 endmodule
-- 
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