[arch][arm] add python app to try to guess stack usage per function

Just a simple app that looks at push and add sp, #num lines to guess
the size of the function. Only tested against thumb2 code.

Generates build-*/lk.stack

arch/arm/rules.mk

@@ -181,4 +181,12 @@ $(BUILDDIR)/system-twosegment.ld: $(LOCAL_DIR)/system-twosegment.ld
 	@$(MKDIR)
 	$(NOECHO)sed "s/%ROMBASE%/$(ROMBASE)/;s/%MEMBASE%/$(MEMBASE)/;s/%MEMSIZE%/$(MEMSIZE)/" < $< > $@
 
+# arm specific script to try to guess stack usage
+$(OUTELF).stack: LOCAL_DIR:=$(LOCAL_DIR)
+$(OUTELF).stack: $(OUTELF).lst
+	$(NOECHO)echo generating stack usage $@
+	$(NOECHO)$(LOCAL_DIR)/stackusage < $< | sort -n -k 1 -r > $@
+
+EXTRA_BUILDDEPS += $(OUTELF).stack
+
 include make/module.mk

arch/arm/stackusage

@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+
+import sys
+import re
+
+hexrule = re.compile("([0-9a-fA-F]+)")
+hex2byterule = re.compile("([0-9a-fA-F]{4})")
+hexcolonrule = re.compile("([0-9a-fA-F]+)\:")
+symbolrule = re.compile("<([_a-zA-Z]+[_0-9a-zA-Z]*)>:")
+insrule = re.compile("([a-zA-Z][\.a-zA-Z]*)")
+
+currsymbol = ""
+curraddress = 0
+
+for line in sys.stdin:
+	t = line.split()
+
+	if len(t) == 0:
+		continue
+
+	try:
+		count = 0
+
+		# match the address
+		match = hexcolonrule.match(t[0])
+		if match:
+			#print "%s %s" % (match, match.group(1))
+			curraddress = int(match.group(1), 16)
+			#print "curraddress 0x%x" % curraddress
+
+		# see if this is a symbol declaration
+		match = symbolrule.match(t[1])
+		if match:
+			#print "%s %s" % (match, match.group(1))
+			currsymbol = str(match.group(1))
+			#print "current symbol is now '%s'" % currsymbol
+			continue
+
+		# see if it's a one or two byte opcode
+		iindex = 2
+		match = hex2byterule.match(t[1])
+		if not match:
+			continue
+		match = hex2byterule.match(t[2])
+		if match:
+			#print "match %s, %s" % (match, match.group(0))
+			iindex = 3
+
+		#print "instruction starts at index %d: '%s'" % (iindex, t[iindex])
+
+		# match the instruction string
+		insmatch = insrule.match(t[iindex])
+		if not insmatch:
+			continue
+		ins = insmatch.group(1)
+		#print "instruction '%s'" % ins
+
+		# look for a few special instructions
+		if ins == "push":
+			count = (len(t) - 1 - iindex) * 4
+			#print "%d words pushed" % count
+
+		if ins == "sub":
+			reg = t[iindex+1]
+			if reg == "sp,":
+				conststr = t[iindex+2]
+				count = int(conststr[1:])
+				#print "subtracting from sp, val %d" % count
+
+		# if we found a stack offset, print it
+		if count > 0:
+			print "%d %s" % (count, currsymbol)
+
+	except IndexError:
+		continue
+	except Exception as e:
+		print "Exception %s" % e
+		continue