[clang] [HLSL] add loop unroll (PR #93879)

[Farzon Lotfi via cfe-commits]

================
@@ -0,0 +1,99 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: dxil-pc-shadermodel6.3-library %s -emit-llvm -o - | FileCheck %s
+
+/*** for ***/
+void for_count()
+{
+// CHECK-LABEL: for_count
----------------
farzonl wrote:

`Are we guaranteed`
No these are typically just hints, also  these tests aren't running without any optimizations, i'll make that more explicit by adding `-disable-llvm-passes` back. 

https://github.com/llvm/llvm-project/pull/93879