OVN expressions need to know what fields overlap or alias one another.
This is supposed to be done via subfields: if two fields overlap, then the
smaller one should be defined as a subfield of the larger one. For
example, reg0 should be defined as xxreg0[96..127]. The symbol table in
lflow didn't do this, so it's possible for confusion to result. (I don't
have evidence of this actually happening, because it would only occur
in a case where the same bits of a field were referred to with different
names.)
This commit fixes the problem. It deserves a test, but that's somewhat
difficult at this point, so it will actually happen in a future commit.
Signed-off-by: Ben Pfaff <b...@ovn.org>
---
ovn/controller/lflow.c | 50 +++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 45 insertions(+), 5 deletions(-)
diff --git a/ovn/controller/lflow.c b/ovn/controller/lflow.c
index 9eb92c8..71d42a7 100644
--- a/ovn/controller/lflow.c
+++ b/ovn/controller/lflow.c
@@ -52,6 +52,20 @@ lflow_reset_processing(void)
physical_reset_processing();
}
+static void
+add_subregister(const char *name,
+ const char *parent_name, int parent_idx,
+ int width, int idx,
+ struct shash *symtab)
+{
+ int lsb = width * idx;
+ int msb = lsb + (width - 1);
+ char *expansion = xasprintf("%s%d[%d..%d]",
+ parent_name, parent_idx, lsb, msb);
+ expr_symtab_add_subfield(symtab, name, NULL, expansion);
+ free(expansion);
+}
+
void
lflow_init(void)
{
@@ -64,16 +78,42 @@ lflow_init(void)
expr_symtab_add_string(&symtab, "inport", MFF_LOG_INPORT, NULL);
expr_symtab_add_string(&symtab, "outport", MFF_LOG_OUTPORT, NULL);
- /* Logical registers. */
+ /* Logical registers:
+ * 128-bit xxregs
+ * 64-bit xregs
+ * 32-bit regs
+ *
+ * The expression language doesn't handle overlapping fields properly
+ * unless they're formally defined as subfields. It's a little awkward. */
+ for (int xxi = 0; xxi < MFF_N_LOG_REGS / 4; xxi++) {
+ char *xxname = xasprintf("xxreg%d", xxi);
+ expr_symtab_add_field(&symtab, xxname, MFF_XXREG0 + xxi, NULL, false);
+ free(xxname);
+ }
+ for (int xi = 0; xi < MFF_N_LOG_REGS / 2; xi++) {
+ char *xname = xasprintf("xreg%d", xi);
+ int xxi = xi / 2;
+ if (xxi < MFF_N_LOG_REGS / 4) {
+ add_subregister(xname, "xxreg", xxi, 64, 1 - xi % 2, &symtab);
+ } else {
+ expr_symtab_add_field(&symtab, xname, MFF_XREG0 + xi, NULL, false);
+ }
+ free(xname);
+ }
for (int i = 0; i < MFF_N_LOG_REGS; i++) {
char *name = xasprintf("reg%d", i);
- expr_symtab_add_field(&symtab, name, MFF_LOG_REG0 + i, NULL, false);
+ int xxi = i / 4;
+ int xi = i / 2;
+ if (xxi < MFF_N_LOG_REGS / 4) {
+ add_subregister(name, "xxreg", xxi, 32, 3 - i % 4, &symtab);
+ } else if (xi < MFF_N_LOG_REGS / 2) {
+ add_subregister(name, "xreg", xi, 32, 1 - i % 2, &symtab);
+ } else {
+ expr_symtab_add_field(&symtab, name, MFF_REG0 + i, NULL, false);
+ }
free(name);
}
- expr_symtab_add_field(&symtab, "xxreg0", MFF_XXREG0, NULL, false);
- expr_symtab_add_field(&symtab, "xxreg1", MFF_XXREG1, NULL, false);
-
/* Flags used in logical to physical transformation. */
expr_symtab_add_field(&symtab, "flags", MFF_LOG_FLAGS, NULL, false);
char flags_str[16];
--
2.1.3
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