...

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/dis.h b/lib/dis.h
new file mode 100644
index 0000000..8063235
--- /dev/null
+++ b/lib/dis.h
@@ -0,0 +1,47 @@
+#pragma once
+
+static inline int sext(unsigned val, int bits) {
+    return val & (1 << (bits - 1)) ? ((int)val - (1 << bits)) : (int)val;
+}
+
+struct bitslice_run {
+    int inpos, outpos, len;
+};
+
+struct bitslice {
+    int nruns;
+    const struct bitslice_run *runs;
+};
+
+__attribute__((always_inline))
+static inline unsigned bs_get(struct bitslice bs, unsigned op) {
+    unsigned ret = 0;
+    for(int i = 0; i < bs.nruns; i++) {
+        const struct bitslice_run *run = &bs.runs[i];
+        unsigned masked = op & ((1 << run->len) - 1);
+        if (run->outpos < run->inpos)
+            masked >>= run->inpos - run->outpos;
+        else if (run->outpos > run->inpos)
+            masked <<= run->outpos - run->inpos;
+        ret |= masked;
+    }
+    return ret;
+}
+
+__attribute__((always_inline))
+static inline unsigned bs_set(struct bitslice bs, unsigned val, unsigned op) {
+    for(int i = 0; i < bs.nruns; i++) {
+        const struct bitslice_run *run = &bs.runs[i];
+        unsigned mask = (1 << run->len) - 1;
+        unsigned masked = val & mask;
+        if (run->outpos < run->inpos) {
+            masked <<= run->inpos - run->outpos;
+            mask <<= run->inpos - run->outpos;
+        } else if (run->outpos > run->inpos) {
+            masked >>= run->outpos - run->inpos;
+            mask >>= run->outpos - run->inpos;
+        }
+        op = (op & ~mask) | masked;
+    }
+    return op;
+}