Add instructional forward-example.

Author: ludgerpaehler

7_fwd/Makefile

@@ -0,0 +1,10 @@
+all: fwd.o
+
+clean:
+	rm -f *.o *.ll
+
+%.o: %.c
+	../dockerscript.sh clang-12 /host/$^ -O3 -Xclang -load -Xclang /Enzyme/enzyme/build/Enzyme/ClangEnzyme-12.so -ffast-math -o /host/$@
+
+run-%: %.o
+	../dockerscript.sh /host/$^ 3.14

7_fwd/fwd.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <math.h>
+#include <assert.h>
+
+double __enzyme_fwddiff(void*, ...);
+
+void compute_loops(float* a, float* b, float* ret) {
+  double sum0 = 0.0;
+  for (int i = 0; i < 100; i++) {
+    sum0 += *a + *b;
+  }
+  *ret = sum0;
+}
+
+int main(int argc, char** argv) {
+  float a = 2.0;
+  float b = 3.0;
+
+  float da = 1.0;//(float*) malloc(sizeof(float));
+  float db = 1.0;//(float*) malloc(sizeof(float));
+
+  float ret = 0;
+  float dret = 1.0;
+
+  __enzyme_fwddiff(compute_loops, &a, &da, &b, &db, &ret, &dret);
+  printf("ret %f, dret %f, da: %f, db: %f\n", ret, dret, da, db);
+
+  return 0;
+}