Do not reset pc_changed and sv_changed at instruction end

We need these outputs to hold stable, so the Issue FSM can know whether
it can return to the Simple-V loop, or must return to Fetch. A good place
to reset these is at the start, before any instruction is executed.

diff --git a/src/soc/simple/issuer.py b/src/soc/simple/issuer.py
index 877c73829017aee8885687585e3305ae1ad6a1b9..f1e197eac06e7f2faa043993fb66b6d4a9f38df2 100644 (file)
--- a/src/soc/simple/issuer.py
+++ b/src/soc/simple/issuer.py
@@ -369,6 +369,8 @@ class TestIssuerInternal(Elaboratable):
                 with m.If(exec_insn_valid_i):
                     comb += core_ivalid_i.eq(1)  # instruction is valid
                     comb += core_issue_i.eq(1)  # and issued
                 with m.If(exec_insn_valid_i):
                     comb += core_ivalid_i.eq(1)  # instruction is valid
                     comb += core_issue_i.eq(1)  # and issued

+                    sync += sv_changed.eq(0)
+                    sync += pc_changed.eq(0)

                     m.next = "INSN_ACTIVE"  # move to "wait completion"
 
             # instruction started: must wait till it finishes
                     m.next = "INSN_ACTIVE"  # move to "wait completion"
 
             # instruction started: must wait till it finishes


@@ -385,8 +387,6 @@ class TestIssuerInternal(Elaboratable):
                     sync += core.e.eq(0)
                     sync += core.raw_insn_i.eq(0)
                     sync += core.bigendian_i.eq(0)
                     sync += core.e.eq(0)
                     sync += core.raw_insn_i.eq(0)
                     sync += core.bigendian_i.eq(0)

-                    sync += sv_changed.eq(0)
-                    sync += pc_changed.eq(0)

                     comb += exec_pc_valid_o.eq(1)
                     with m.If(exec_pc_ready_i):
                         m.next = "INSN_START"  # back to fetch
                     comb += exec_pc_valid_o.eq(1)
                     with m.If(exec_pc_ready_i):
                         m.next = "INSN_START"  # back to fetch