fixes #14623; Top-level volatileLoad/volatileStore leads to invalid codegen (#24020)

fixes #14623

lib/pure/volatile.nim

@@ -10,20 +10,18 @@
 ## This module contains code for generating volatile loads and stores,
 ## which are useful in embedded and systems programming.
 
-template volatileLoad*[T](src: ptr T): T =
+proc volatileLoad*[T](src: ptr T): T {.inline, noinit.} =
   ## Generates a volatile load of the value stored in the container `src`.
   ## Note that this only effects code generation on `C` like backends.
   when nimvm:
-    src[]
+    result = src[]
   else:
     when defined(js):
-      src[]
+      result = src[]
     else:
-      var res: T
-      {.emit: [res, " = (*(", typeof(src[]), " volatile*)", src, ");"].}
-      res
+      {.emit: [result, " = (*(", typeof(src[]), " volatile*)", src, ");"].}
 
-template volatileStore*[T](dest: ptr T, val: T) =
+proc volatileStore*[T](dest: ptr T, val: T) {.inline.} =
   ## Generates a volatile store into the container `dest` of the value
   ## `val`. Note that this only effects code generation on `C` like
   ## backends.

tests/stdlib/tvolatile.nim

@@ -0,0 +1,15 @@
+import std/[volatile, assertions]
+
+var st: int
+var foo: ptr int = addr st
+volatileStore(foo, 12)
+doAssert volatileLoad(foo) == 12
+
+# bug #14623
+proc bar =
+  var st: int
+  var foo: ptr int = addr st
+  volatileStore(foo, 12)
+  doAssert volatileLoad(foo) == 12
+
+bar()