From de5681429e93c53a03129fcd7683dc068b0696fb Mon Sep 17 00:00:00 2001
From: teoxoy <28601907+teoxoy@users.noreply.github.com>
Date: Wed, 20 Sep 2023 13:09:25 +0200
Subject: [PATCH] [msl-out] add min version check for `reverse_bits`,
 `extract_bits` & `insert_bits`

---
 src/back/msl/mod.rs    |  2 ++
 src/back/msl/writer.rs | 24 +++++++++++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/back/msl/mod.rs b/src/back/msl/mod.rs
index f6ea6d42b9..76e0c39e1b 100644
--- a/src/back/msl/mod.rs
+++ b/src/back/msl/mod.rs
@@ -129,6 +129,8 @@ pub enum Error {
     CapabilityNotSupported(crate::valid::Capabilities),
     #[error("attribute '{0}' is not supported for target MSL version")]
     UnsupportedAttribute(String),
+    #[error("function '{0}' is not supported for target MSL version")]
+    UnsupportedFunction(String),
     #[error("can not use writeable storage buffers in fragment stage prior to MSL 1.2")]
     UnsupportedWriteableStorageBuffer,
     #[error("can not use writeable storage textures in {0:?} stage prior to MSL 1.2")]
diff --git a/src/back/msl/writer.rs b/src/back/msl/writer.rs
index 5eebdaffa7..30310080b2 100644
--- a/src/back/msl/writer.rs
+++ b/src/back/msl/writer.rs
@@ -502,6 +502,7 @@ struct ExpressionContext<'a> {
     info: &'a valid::FunctionInfo,
     module: &'a crate::Module,
     pipeline_options: &'a PipelineOptions,
+    lang_version: (u8, u8),
     policies: index::BoundsCheckPolicies,
 
     /// A bitset containing the `Expression` handle indexes of expressions used
@@ -1758,9 +1759,24 @@ impl<W: Write> Writer<W> {
                     Mf::CountTrailingZeros => "ctz",
                     Mf::CountLeadingZeros => "clz",
                     Mf::CountOneBits => "popcount",
-                    Mf::ReverseBits => "reverse_bits",
-                    Mf::ExtractBits => "extract_bits",
-                    Mf::InsertBits => "insert_bits",
+                    Mf::ReverseBits | Mf::ExtractBits | Mf::InsertBits => {
+                        let name = match fun {
+                            // reverse_bits is listed as requiring MSL 2.1 but that is copy/paste error.
+                            // Looking at previous snapshots on web.archive.org it's present in MSL 1.2.
+                            //
+                            // https://developer.apple.com/library/archive/documentation/Miscellaneous/Conceptual/MetalProgrammingGuide/WhatsNewiniOS10tvOS10andOSX1012/WhatsNewiniOS10tvOS10andOSX1012.html
+                            // also talks about MSL 1.2 adding "New integer functions to extract, insert, and reverse bits, as described in Integer Functions."
+                            Mf::ReverseBits => "reverse_bits",
+                            Mf::ExtractBits => "extract_bits",
+                            Mf::InsertBits => "insert_bits",
+                            _ => unreachable!(),
+                        };
+                        if context.lang_version < (1, 2) {
+                            return Err(Error::UnsupportedFunction(name.to_string()));
+                        } else {
+                            name
+                        }
+                    }
                     Mf::FindLsb => "",
                     Mf::FindMsb => "",
                     // data packing
@@ -3566,6 +3582,7 @@ impl<W: Write> Writer<W> {
                     function: fun,
                     origin: FunctionOrigin::Handle(fun_handle),
                     info: fun_info,
+                    lang_version: options.lang_version,
                     policies: options.bounds_check_policies,
                     guarded_indices,
                     module,
@@ -4150,6 +4167,7 @@ impl<W: Write> Writer<W> {
                     function: fun,
                     origin: FunctionOrigin::EntryPoint(ep_index as _),
                     info: fun_info,
+                    lang_version: options.lang_version,
                     policies: options.bounds_check_policies,
                     guarded_indices,
                     module,