RISC-V: implement WFI in the platform model.

The initial implementation tries to optimize for simulator execution, especially for OS boots.

1 files changed, 12 insertions, 0 deletions

diff --git a/riscv/riscv_platform.sail b/riscv/riscv_platform.sail
index c878f2a7..aee72e47 100644
--- a/riscv/riscv_platform.sail
+++ b/riscv/riscv_platform.sail
@@ -281,3 +281,15 @@ function handle_illegal() -> unit = {
                                     excinfo = info };
   nextPC = handle_exception(cur_privilege, CTL_TRAP(t), PC)
 }
+
+/* Platform-specific wait-for-interrupt */
+
+function platform_wfi() -> unit = {
+  /* speed execution by getting the timer to fire at the next instruction,
+   * since we currently don't have any other devices raising interrupts.
+   */
+  if mtime <_u mtimecmp then {
+    mtime  = mtimecmp;
+    mcycle = mtimecmp;
+  }
+}
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