From eb053503f7f1a8215d4464cd0333a39e24a7dc9f Mon Sep 17 00:00:00 2001
From: Graham Edgecombe <gpe@grahamedgecombe.com>
Date: Sat, 2 Dec 2017 17:17:26 +0000
Subject: [PATCH] Populate instr_mem with a test assembly program

---
 .gitignore    |  2 ++
 Makefile      | 26 +++++++++++++++++++++-----
 progmem.s     |  3 +++
 rv32_fetch.sv |  3 +++
 4 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 progmem.s

diff --git a/.gitignore b/.gitignore
index 21350b0..af61409 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,5 +3,7 @@
 *.asc
 *.bin
 *.blif
+*.hex
+*.o
 !.git*
 !.mailmap
diff --git a/Makefile b/Makefile
index 8e1c59b..8e65359 100644
--- a/Makefile
+++ b/Makefile
@@ -3,6 +3,7 @@ SRC      = $(wildcard *.sv)
 TOP      = top
 YS       = $(TOP).ys
 BLIF     = $(TOP).blif
+ASC_SYN  = $(TOP)_syn.asc
 ASC      = $(TOP).asc
 BIN      = $(TOP).bin
 SPEED    = hx
@@ -10,27 +11,42 @@ DEVICE   = 8k
 PACKAGE  = ct256
 PCF      = ice40hx8k-b-evn.pcf
 FREQ_OSC = 12
+TARGET   = riscv64-unknown-elf
+AS       = $(TARGET)-as
+ASFLAGS  = -march=rv32i -mabi=ilp32
+OBJCOPY  = $(TARGET)-objcopy
 
 .PHONY: all clean time stat flash
 
 all: $(TOP).bin
 
 clean:
-	$(RM) $(BLIF) $(ASC) $(BIN)
+	$(RM) $(BLIF) $(ASC_SYN) $(ASC) $(BIN) progmem_syn.hex progmem.hex progmem.o
 
-$(BLIF): $(YS) $(SRC)
+progmem.hex: progmem.o
+	$(OBJCOPY) -O srec $< /dev/stdout \
+		| srec_cat - -byte-swap 4 -output - -binary \
+		| xxd -p -c 4 > $@
+
+progmem_syn.hex:
+	icebram -g 32 256 > $@
+
+$(BLIF): $(YS) $(SRC) progmem_syn.hex
 	yosys $(QUIET) -s $<
 
-$(ASC): $(BLIF) $(PCF)
+$(ASC_SYN): $(BLIF) $(PCF)
 	arachne-pnr $(QUIET) -d $(DEVICE) -P $(PACKAGE) -o $@ -p $(PCF) $<
 
+$(ASC): $(ASC_SYN) progmem_syn.hex progmem.hex
+	icebram progmem_syn.hex progmem.hex < $< > $@
+
 $(BIN): $(ASC)
 	icepack $< $@
 
-time: $(ASC) $(PCF)
+time: $(ASC_SYN) $(PCF)
 	icetime -t -m -d $(SPEED)$(DEVICE) -P $(PACKAGE) -p $(PCF) -c $(FREQ_OSC) $<
 
-stat: $(ASC)
+stat: $(ASC_SYN)
 	icebox_stat $<
 
 flash: $(BIN)
diff --git a/progmem.s b/progmem.s
new file mode 100644
index 0000000..7244e4a
--- /dev/null
+++ b/progmem.s
@@ -0,0 +1,3 @@
+start:
+  addi x31, x31, 1
+  j start
diff --git a/rv32_fetch.sv b/rv32_fetch.sv
index 1e9205e..a6cb032 100644
--- a/rv32_fetch.sv
+++ b/rv32_fetch.sv
@@ -19,6 +19,9 @@ module rv32_fetch (
 
     logic [31:0] pc = branch_taken_in ? branch_pc_in : next_pc;
 
+    initial
+        $readmemh("progmem_syn.hex", instr_mem);
+
     always_ff @(posedge clk) begin
         instr_out <= instr_mem[pc[31:2]];
         next_pc <= pc + 4;