diff --git a/llrtc/Makefile b/llrtc/Makefile
index c271d0e..bde100e 100644
--- a/llrtc/Makefile
+++ b/llrtc/Makefile
@@ -1,21 +1,22 @@
-DIRECTORIES = divmod
-
 all:
-	for mydir in $(DIRECTORIES); do \
-		make -C $$mydir; \
-	done
+	make -C lib
+
+ir:
+	make -C lib ir
 
 test:
-	for mydir in $(DIRECTORIES); do \
-		make -C $$mydir test; \
-	done
+	make -C lib test
 
 clean-test:
-	for mydir in $(DIRECTORIES); do \
-		make -C $$mydir clean-test; \
-	done
+	make -C lib clean-test
+
+clean-temp:
+	make -C lib clean-temp
 
 clean:
-	for mydir in $(DIRECTORIES); do \
-		make -C $$mydir clean; \
-	done
\ No newline at end of file
+	make -C lib clean
+
+install: ir
+	make -C lib clean-test
+	make -C lib clean-temp
+	
\ No newline at end of file
diff --git a/llrtc/common.mk b/llrtc/common.mk
deleted file mode 100644
index 3de9c12..0000000
--- a/llrtc/common.mk
+++ /dev/null
@@ -1,26 +0,0 @@
-CLANG = clang
-CF = -Wall -ansi
-OUTDIR = ..
-
-all: ir
-
-$(OUTPUT).c:  $(OUTPUT).h
-
-$(OUTPUT): test.c $(OUTPUT).c
-	$(CLANG) $(CF) -ftrapv -o $@ $+
-
-test: $(OUTPUT)
-	python test.py
-
-ir: 	
-	CLANG -m32 $(CF) -O0 -emit-llvm -S $(OUTPUT).c -o $(OUTDIR)/x86/$(OUTPUT).ll
-	CLANG -m64 $(CF) -O0 -emit-llvm -S $(OUTPUT).c -o $(OUTDIR)/x86_64/$(OUTPUT).ll
-	python ../tools/striptriple.py $(OUTDIR)/x86/$(OUTPUT).ll
-	python ../tools/striptriple.py $(OUTDIR)/x86_64/$(OUTPUT).ll
-
-clean-test:
-	rm -f $(OUTPUT)
-
-clean: clean-test
-	rm -f $(OUTDIR)/x86/$(OUTPUT).ll
-	rm -f $(OUTDIR)/x86_64/$(OUTPUT).ll
diff --git a/llrtc/lib/.gitignore b/llrtc/lib/.gitignore
new file mode 100644
index 0000000..fbcf76a
--- /dev/null
+++ b/llrtc/lib/.gitignore
@@ -0,0 +1,4 @@
+*.o
+*.run
+*.out
+*.ll
diff --git a/llrtc/lib/Makefile b/llrtc/lib/Makefile
index 1bb325f..8c9361d 100644
--- a/llrtc/lib/Makefile
+++ b/llrtc/lib/Makefile
@@ -1,44 +1,66 @@
 OUTPUT = llrt
-SOURCES = udivmod64.c
+SOURCES = udivmod64.c sdivmod64.c
+TESTS = test_udivmod64.c test_sdivmod64.c
 
 CLANG = clang
+LLVM_LINK = llvm-link
 CF = -Wall -ansi
 CF_TEST = $(CF) -ftrapv
 CF_BUILD = $(CF) -O0 -emit-llvm
 OUTDIR = ..
+STRIPPER = ../tools/striptriple.py
 
 all: ir
 
-ir: $(SOURCES)
-	$(CLANG) -m32 $(CF_BUILD) -S -o $(OUTDIR)/$(OUTPUT)_x86.ll -c $(SOURCES)
-	python ../tools/striptriple.py $(OUTDIR)/$(OUTPUT)_x86.ll
-	$(CLANG) -m64 $(CF_BUILD) -S -o $(OUTDIR)/$(OUTPUT)_x86_64.ll -c $(SOURCES)
-	python ../tools/striptriple.py $(OUTDIR)/$(OUTPUT)_x86_64.ll
+ir: $(OUTDIR)/$(OUTPUT)_x86.ll $(OUTDIR)/$(OUTPUT)_x86_64.ll
 
-lib$(OUTPUT).a: $(SOURCES)
-	$(CLANG) $(CF) -o $@ -c $+
+$(OUTDIR)/$(OUTPUT)_x86.ll: $(SOURCES:.c=_x86.bc)
+	$(LLVM_LINK) -S $+ -o $@
+	python $(STRIPPER) $@
 
-build-test:  lib$(OUTPUT).a
-	for src in $(SOURCES); do \
-		$(CLANG) $(CF_TEST) -o test_$${src%.*} test_$$src -L. -lllrt; \
-	done;
+$(OUTDIR)/$(OUTPUT)_x86_64.ll: $(SOURCES:.c=_x86_64.bc)
+	$(LLVM_LINK) -S $+ -o $@
+	python $(STRIPPER) $@
 
-test: build-test
-	for src in $(SOURCES); do \
-		echo "testing $${src%.*}";				 \
-		python test_$${src%.*}.py > test_$${src%.*}.out;	 \
+build-test: $(SOURCES:.c=.o) $(TESTS:.c=.run)
+
+lib$(OUTPUT).a: $(SOURCES:.c=.o)
+	$(CLANG) -static $+ -o $@
+
+test: $(TESTS:.c=.run)
+	for src in $+; do \
+		echo "testing $${src}";				 \
+		python $${src%.*}.py > $${src%.*}.out;	 \
 	done;
 
 clean-test:
 	rm -f *.out
-	rm -f *.a
-	for src in $(SOURCES); do \
-		rm -f test_$${src%.*}	;\
-	done;
+	rm -f *.o
+	rm -f *.run
 
-clean-dist:
-	rm $(OUTDIR)/*.ll
+clean-dist: clean-temp
+	rm -f *.ll
+
+clean-temp:
+	rm -f *.bc
+	rm -f *.o
+	rm -f *.out
 
 clean: clean-test clean-dist
 
-udivmod64.c: udivmod64.h
+%.c: llrt.h
+
+%_x86.bc: %.c
+	$(CLANG) -m32 $(CF_BUILD) -c $< -o $@
+
+%_x86_64.bc: %.c
+	$(CLANG) -m64 $(CF_BUILD) -c $< -o $@
+
+%.o: %.c
+	$(CLANG) $(CF_TEST) -c $<
+
+%.run: %.c
+	$(CLANG) $(CF_TEST) -o $@ $+
+
+test_udivmod64.run: udivmod64.o
+test_sdivmod64.run: udivmod64.o sdivmod64.o
diff --git a/llrtc/lib/udivmod64.h b/llrtc/lib/llrt.h
similarity index 50%
rename from llrtc/lib/udivmod64.h
rename to llrtc/lib/llrt.h
index 9cbcd8c..0d26309 100644
--- a/llrtc/lib/udivmod64.h
+++ b/llrtc/lib/llrt.h
@@ -1,11 +1,12 @@
-#ifndef LLRT_UDIVMOD_H_
-#define LLRT_UDIVMOD_H_
+#ifndef LLRT_H_
+#define LLRT_H_
 
 #include <stdint.h>
 
 #define BITS_PER_BYTE 8
 
 uint64_t udivmod64(uint64_t dividend, uint64_t divisor, uint64_t *remainder);
+int64_t sdivmod64(int64_t dividend, int64_t divisor, int64_t *remainder);
 
-#endif /* LLRT_UDIVMOD_H_ */
+#endif /* LLRT_H_ */
 
diff --git a/llrtc/lib/sdivmod64.c b/llrtc/lib/sdivmod64.c
new file mode 100644
index 0000000..df294b3
--- /dev/null
+++ b/llrtc/lib/sdivmod64.c
@@ -0,0 +1,40 @@
+#include "llrt.h"
+#include <stdio.h>
+
+/*
+Calls to udivmod64 internally.
+Note: remainder uses sign of divisor.
+*/
+int64_t sdivmod64(int64_t dividend, int64_t divisor, int64_t *remainder)
+{
+    int signbitidx = BITS_PER_BYTE * sizeof(dividend) - 1;
+    int signed_dividend = dividend < 0;
+    int signed_divisor = divisor < 0;
+    int signed_result = signed_divisor ^ signed_dividend;
+
+    int64_t quotient;
+    uint64_t udvd, udvr, uquotient, uremainder;
+
+    udvd = signed_dividend ? -dividend : dividend;
+    udvr = signed_divisor ? -divisor : divisor;
+    uquotient = udivmod64(udvd, udvr, &uremainder);
+
+    if (signed_result){
+        if (uremainder) {
+            quotient = -(int64_t)uquotient - 1;
+        } else {
+            quotient = -(int64_t)uquotient;
+        }
+        if (remainder) {
+            /* if signed, there could be unsigned overflow
+               causing undefined behavior */
+            *remainder = (uint64_t)dividend - (uint64_t)quotient * (uint64_t)divisor;
+        }
+    } else {
+        quotient = (int64_t)uquotient;
+        if (remainder) {
+            *remainder = signed_divisor ? -uremainder : uremainder;
+        }
+    }
+    return quotient;
+}
diff --git a/llrtc/lib/test_sdivmod64.c b/llrtc/lib/test_sdivmod64.c
new file mode 100644
index 0000000..1e804d6
--- /dev/null
+++ b/llrtc/lib/test_sdivmod64.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <stdint.h>
+#include "llrt.h"
+
+int main(int argc, char * argv[]){
+    int64_t n, d, q, r;
+
+    if (argc != 3) {
+        printf("invalid argument: %s dividend divisor", argv[0]);
+        return 1;
+    }
+    sscanf(argv[1], "%lld", &n);
+    sscanf(argv[2], "%lld", &d);
+
+    q = sdivmod64(n, d, &r);
+
+    printf("%lld\n", q);
+    printf("%lld\n", r);
+
+    return 0;
+}
diff --git a/llrtc/lib/test_sdivmod64.py b/llrtc/lib/test_sdivmod64.py
new file mode 100644
index 0000000..4aa49a9
--- /dev/null
+++ b/llrtc/lib/test_sdivmod64.py
@@ -0,0 +1,56 @@
+import math
+import os
+import subprocess
+udt = os.path.join('.', 'test_sdivmod64.run')
+
+def testcase(dividend, divisor):
+    print 'divmod64(%d, %d)' % (dividend, divisor)
+
+    procargs = ('%s %s %s' % (udt, dividend, divisor)).split()
+    result = subprocess.check_output(procargs)
+    gotQ, gotR = map(int, result.splitlines())
+
+    expectQ = dividend // divisor
+    expectR = dividend % divisor
+
+    print 'Q = %d, R = %d' % (gotQ, gotR)
+
+    if expectQ != gotQ:
+        raise ValueError("invalid quotient: got=%d but expect=%d" %
+                         (gotQ, expectQ))
+    if expectR != gotR:
+        raise ValueError("invalid remainder: got=%d but expect=%d" %
+                         (gotR, expectR))
+    print 'OK'
+
+def testsequence():
+    subjects = [
+        (0, 1),
+        (0, 0xffffffff),
+        (1, 2),
+        (1, 983219),
+        (2, 2),
+        (3, 2),
+        (1024, 2),
+        (2048, 512),
+        (21321, 512),
+        (9329189, 1031),
+        (0xffffffff, 2),
+        (0xffffffff, 0xffff),
+        (0x1ffffffff, 2),
+        (0x1ffffffff, 0xffff),
+        (0xffff, 0xffffffff),
+        (0x0fffffffffffffff, 0xffff),
+        (0x7fffffffffffffff, 0x7fffffffffffffff),
+        (0x7fffffffffffffff, 0x7ffffffffffffff0),
+        (0x7fffffffffffffff, 87655678587161901),
+    ]
+
+    for dvd, dvr in subjects:
+        testcase(dvd, dvr)
+        testcase(dvd, -dvr)
+        testcase(-dvd, dvr)
+        testcase(-dvd, -dvr)
+
+if __name__ == '__main__':
+    testsequence()
diff --git a/llrtc/lib/test_udivmod64.c b/llrtc/lib/test_udivmod64.c
index e2935c5..70b44aa 100644
--- a/llrtc/lib/test_udivmod64.c
+++ b/llrtc/lib/test_udivmod64.c
@@ -1,8 +1,6 @@
 #include <stdio.h>
 #include <stdint.h>
-
-extern uint64_t
-udivmod64(uint64_t dividend, uint64_t divisor, uint64_t *remainder);
+#include "llrt.h"
 
 int main(int argc, char * argv[]){
     uint64_t n, d, q, r;
@@ -19,4 +17,4 @@ int main(int argc, char * argv[]){
     printf("%llu\n", r);
 
     return 0;
-}
\ No newline at end of file
+}
diff --git a/llrtc/lib/test_udivmod64.py b/llrtc/lib/test_udivmod64.py
index 487a458..da07ccb 100644
--- a/llrtc/lib/test_udivmod64.py
+++ b/llrtc/lib/test_udivmod64.py
@@ -1,7 +1,7 @@
 import math
 import os
 import subprocess
-udt = os.path.join('.', 'test_udivmod64')
+udt = os.path.join('.', 'test_udivmod64.run')
 
 def testcase(dividend, divisor):
     print 'divmod64(%d, %d)' % (dividend, divisor)
diff --git a/llrtc/lib/udivmod64.c b/llrtc/lib/udivmod64.c
index a028aea..5936f98 100644
--- a/llrtc/lib/udivmod64.c
+++ b/llrtc/lib/udivmod64.c
@@ -2,7 +2,7 @@
 Implements unsigned divmod using for platform missing 64-bit division and/or
 modulo functions.
 */
-#include "udivmod64.h"
+#include "llrt.h"
 
 /*
 count left zero for 64-bit words
@@ -79,6 +79,6 @@ uint64_t udivmod64(uint64_t dividend, uint64_t divisor, uint64_t *remainder)
             quotient |= 1ull << (63 - i);
         }
     }
-    *remainder = state.tmp;
+    if (remainder) *remainder = state.tmp;
     return quotient;
 }