[clang] [llvm] [HIP] add --offload-compression-level= option (PR #83605)

[Artem Belevich via cfe-commits]

================
@@ -906,6 +906,16 @@ CreateFileHandler(MemoryBuffer &FirstInput,
 }
 
 OffloadBundlerConfig::OffloadBundlerConfig() {
+  if (llvm::compression::zstd::isAvailable()) {
+    CompressionFormat = llvm::compression::Format::Zstd;
+    // Use a high zstd compress level by default for better size reduction.
----------------
Artem-B wrote:

Also, I've just discovered that zstd already has 
https://github.com/facebook/zstd/blob/b293d2ebc3a5d29309390a70b3e7861b6f5133ec/lib/zstd.h#L394

```
    ZSTD_c_enableLongDistanceMatching=160, /* Enable long distance matching.
                                     * This parameter is designed to improve compression ratio
                                     * for large inputs, by finding large matches at long distance.
                                     * It increases memory usage and window size.
                                     * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
                                     * except when expressly set to a different value.
                                     * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
                                     * compression strategy >= ZSTD_btopt (== compression level 16+) */
```

This sounds like something we could use here.

https://github.com/llvm/llvm-project/pull/83605