From 4c6fdb113f644c75751cae625e684ea487944b2d Mon Sep 17 00:00:00 2001
From: Rhys Perry <pendingchaos02@gmail.com>
Date: Fri, 8 Nov 2024 17:07:24 +0000
Subject: [PATCH] nir: fix return value of nir_instr_move for some cases

This fixes a potential issue where nir_opt_move_discards_to_top would
always return progress.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Fixes: f97fb1fa55ca ("nir: Add a nir_instr_move helper")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32145>
---
 src/compiler/nir/nir.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/compiler/nir/nir.c b/src/compiler/nir/nir.c
index 12a2a393a58..946cd628ca8 100644
--- a/src/compiler/nir/nir.c
+++ b/src/compiler/nir/nir.c
@@ -1148,10 +1148,24 @@ nir_instr_move(nir_cursor cursor, nir_instr *instr)
    /* If the cursor happens to refer to this instruction (either before or
     * after), don't do anything.
     */
-   if ((cursor.option == nir_cursor_before_instr ||
-        cursor.option == nir_cursor_after_instr) &&
-       cursor.instr == instr)
-      return false;
+   switch (cursor.option) {
+   case nir_cursor_before_instr:
+      if (cursor.instr == instr || nir_instr_prev(cursor.instr) == instr)
+         return false;
+      break;
+   case nir_cursor_after_instr:
+      if (cursor.instr == instr || nir_instr_next(cursor.instr) == instr)
+         return false;
+      break;
+   case nir_cursor_before_block:
+      if (cursor.block == instr->block && nir_instr_is_first(instr))
+         return false;
+      break;
+   case nir_cursor_after_block:
+      if (cursor.block == instr->block && nir_instr_is_last(instr))
+         return false;
+      break;
+   }
 
    nir_instr_remove(instr);
    nir_instr_insert(cursor, instr);