start working on DTB printer

3 files changed, 177 insertions, 2 deletions

diff --git a/examples/device_tree.subv b/examples/device_tree.subv
new file mode 100644
index 0000000..b2b0022
--- /dev/null
+++ b/examples/device_tree.subv
@@ -0,0 +1,152 @@
+== code 0x80400000
+main:
+# print device tree info.
+# OpenSBI calls us with a1 set to the start of the DTB
+  # load 0x10000000 (UART0) into a0
+  37/lui a/rd/a0 10000/imm20
+
+  13/opi 15/rd/s5 0/subop/add b/rs/a1 0/imm12
+
+  # check magic == 0xd00dfeed
+  37/lui 6/rd/t1 edfe1dd0/imm20hi
+  13/opi 6/rd/t1 0/subop/add 6/rs/t1 edfe0dd0/imm12lo
+  03/load 5/rd/t0 2/width/w 15/rs/s5 0/imm12
+  63/branch 1/subop/!= 5/rs/t0 6/rs/t1 err_magic/off13
+
+  37/lui b/rd/a1 S_TOTALSZ/imm20hi
+  13/opi b/rd/a1 0/subop/add b/rs/a1 S_TOTALSZ/imm12lo
+  6f/jal 1/rd/ra print/off21
+
+  03/load b/rd/a1 2/width/w 15/rs/s5 4/imm12
+  6f/jal 1/rd/ra bswapw/off21
+  6f/jal 1/rd/ra print_hex_word/off21
+  6f/jal 1/rd/ra printnl/off21
+
+exit:
+# system reset (via SBI extension SRST)
+  # a7 = ext id, a6 = fid, a0 = 0, a1 = 0
+  37/lui 11/rd/a7 53525/imm20
+  13/opi 11/rd/a7 0/subop/add 11/rs/a7 354/imm12
+  33/opr 0/mode/norm 10/rd/a6 0/subop/add 0/rs/x0 0/rs/x0
+  33/opr 0/mode/norm a/rd/a0 0/subop/add 0/rs/x0 0/rs/x0
+  33/opr 0/mode/norm b/rd/a1 0/subop/add 0/rs/x0 0/rs/x0
+  # ECALL
+  73/system 0/subop/priv 0/funct12/ecall
+
+err_magic:
+  37/lui b/rd/a1 E_MAGIC/imm20hi
+  13/opi b/rd/a1 0/subop/add b/rs/a1 E_MAGIC/imm12lo
+  6f/jal 1/rd/ra print/off21
+  6f/jal 0/rd/x0 exit/off21
+
+bswapw:
+# byte-order-swap word in a1
+  # srli    a1, a0, 8
+  # lui     a2, 16
+  # addi    a2, a2, -256
+  # and     a1, a1, a2
+  13/opi 5/rd/t0 5/subop/srl b/rs/a1 8/imm12
+  37/lui 6/rd/t1 16/imm20
+  13/opi 6/rd/t1 0/subop/add 6/rs/t1 -100/imm12
+  33/opr 5/rd/t0 7/subop/and 0/mode/norm 5/rs/t0 6/rs/t1
+  #  srli    a2, a0, 24
+  #  or      a1, a1, a2
+  13/opi 6/rd/t1 5/subop/srl b/rs/a1 18/imm12
+  33/opr 5/rd/t0 6/subop/or 0/mode/norm 5/rs/t0 6/rs/t1
+  # slli    a2, a0, 8
+  # lui     a3, 4080
+  # and     a2, a2, a3
+  13/opi 6/rd/t1 1/subop/sll 0/mode/norm b/rs/a1 8/imm5
+  37/lui 7/rd/t2 ff0/imm20
+  33/opr 6/rd/t1 7/subop/and 0/mode/norm 6/rs/t1 7/rs/t2
+  # slli    a0, a0, 24
+  # or      a0, a0, a2
+  # or      a0, a0, a1
+  13/opi b/rd/a1 1/subop/sll 0/mode/norm b/rs/a1 18/imm5
+  33/opr b/rd/a1 6/subop/or 0/mode/norm b/rs/a1 6/rs/t1
+  33/opr b/rd/a1 6/subop/or 0/mode/norm b/rs/a1 5/rs/t0
+  # ret
+  67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
+
+printnl:
+  13/opi 6/rd/t1 0/subop/add 0/rs/x0 0a/imm12
+printnl:spin:
+  # spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
+  03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
+  13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
+  63/branch 0/subop/== 7/rs/t2 0/rs/x0 printnl:spin/off13
+  # print char
+  23/store 2/width/w a/rs/a0 0/off12 6/rs/t1
+  # return
+  67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
+
+print:
+print:loop:
+  # load unsigned byte at a1
+  03/load 6/rd/t1 4/width/bu b/rs/a1 0/imm12
+  # break loop if zero
+  63/branch 0/subop/== 6/rs/t1 0/rs/x0 print:break/off13
+print:spin:
+  # spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
+  03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
+  13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
+  63/branch 0/subop/== 7/rs/t2 0/rs/x0 print:spin/off13
+  # print char
+  23/store 2/width/w a/rs/a0 0/off12 6/rs/t1
+  # increment a1
+  13/opi b/rd/a1 0/subop/add b/rs/a1 1/imm12
+  # jump back up
+  6f/jal 0/rd/x0 print:loop/off21
+print:break:
+  # return
+  67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
+
+print_hex_word:
+  13/opi 8/rd/s0 0/subop/add b/rs/a1 0/imm12
+  13/opi 9/rd/s1 0/subop/add 0/rs/x0 1c/imm12
+  13/opi 12/rd/s2 0/subop/add 1/rs/ra 0/imm12
+print_hex_word:loop:
+  # shift
+  33/opr b/rd/a1 5/subop/srl 8/rs/s0 0/funct7/norm 9/rs/s1
+  6f/jal 1/rd/ra print_hex_dgt/off21
+
+  # break if last shift
+  63/branch 9/rs/s1 0/subop/== 0/rs/x0 print_hex_word:break/off13
+
+  # subtract shift count, loop
+  13/opi 9/rd/s1 0/subop/add 9/rs/s1 -4/imm12
+  6f/jal 0/rd/x0 print_hex_word:loop/off21
+  print_hex_word:break:
+  # return
+  67/jalr 0/rd/x0 0/subop 12/rs/s2 0/off12
+
+print_hex_dgt:
+  # a1 = a1 & 0xf
+  13/opi b/rd/a1 7/subop/and b/rs/a1 f/imm12
+  # t1 = 0x40
+  13/opi 6/rd/t1 0/subop/add 0/rs/x0 40/imm12
+
+  # add 0x30 (ascii '0') / 0x61 (ascii 'a')
+  13/opi b/rd/a1 0/subop/add b/rs/a1 30/imm12
+  63/branch b/rs/a1 4/subop/< 6/rs/t1 print_hex_dgt:spin/off13
+  13/opi b/rd/a1 0/subop/add b/rs/a1 27/imm12
+
+print_hex_dgt:spin:
+  # spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
+  03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
+  13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
+  63/branch 0/subop/== 7/rs/t2 0/rs/x0 print_hex_dgt:spin/off13
+
+  # print char
+  23/store 2/width/w a/rs/a0 0/off12 b/rs/a1
+
+  # return
+  67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
+
+== data 0x80500000
+E_MAGIC:
+  # "Invalid DTB magic!\n\0"
+  49/8 6e/8 76/8 61/8 6c/8 69/8 64/8 20/8 44/8 54/8 42/8 20/8 6d/8 61/8 67/8 69/8 63/8 21/8 0a/8 00/8
+S_TOTALSZ:
+  54/8 6f/8 74/8 61/8 6c/8 20/8 53/8 69/8 7a/8 65/8 3a/8 20/8 00/8
+
diff --git a/survey.py b/survey.py
index 69f6120..7dd32c9 100755
--- a/survey.py
+++ b/survey.py
@@ -128,7 +128,28 @@ def observe(word, pc, map):
     ValueError: label reference out of range (8 bit): 'label' (0x1234)
     """
     if not subv.is_reference(word):
-        return word
+        if len(word) != 2:
+            return word
+
+        ref = subv.parse_immediate(word[1])
+        if not ref or "split" not in ref:
+            return word
+
+        value = word[0]
+
+        sgn = -1 if value < 0 else 1
+        value *= sgn
+
+        if ref["split"] == "hi" and ref["size"] == 20:
+            value = value >> 12
+        elif ref["split"] == "lo" and ref["size"] == 12:
+            value = value & 0xFFF
+        else:
+            raise ValueError(
+                "unknown label split mode {mode}{size}{split}".format(**ref)
+            )
+
+        return (value, "imm{size}".format(**ref))
 
     ref = subv.parse_reference(word)
 
diff --git a/validate.py b/validate.py
index 2e46a9b..9950d07 100755
--- a/validate.py
+++ b/validate.py
@@ -363,7 +363,9 @@ def validate_opi(inputs):
     if funct[2] in ["sll", "srl", "sra"]:
         try:
             shamt = pop_immediate(inputs, 5)
-            mode = pop_immediate(inputs, 7)
+            mode = validate_part(
+                inputs, ["funct7", "mode"], {"norm": 0, "alt": 32}, NAME="comp-mode"
+            )
         except ValueError:
             imm = pop_immediate(inputs, 12)
             shamt = ((imm[0] & 0b11111), 'imm5')