[clang] [llvm] [AArch64] Add ability to list extensions enabled for a target (PR #95805)

[Lucas Duarte Prates via llvm-commits]

================
@@ -19,3 +19,19 @@
 // RUN: %clang --target=arm64 -mlittle-endian -march=armv8.1a -### -c %s 2>&1 | FileCheck -check-prefix=ARM64-GENERICV81A %s
 // RUN: %clang --target=arm64 -mlittle-endian -march=armv8.1-a -### -c %s 2>&1 | FileCheck -check-prefix=ARM64-GENERICV81A %s
 // ARM64-GENERICV81A: "-cc1"{{.*}} "-triple" "arm64{{.*}}" "-target-cpu" "generic"{{.*}} "-target-feature" "+v8.1a"{{.*}} "-target-feature" "+neon"
+
+// ===== Architecture extensions =====
+
+// RUN: %clang -target aarch64 -march=armv8.1-a --print-enabled-extensions 2>&1 | FileCheck -check-prefix=ARCH-EXTENSION --implicit-check-not FEAT_ %s
+// ARCH-EXTENSION: FEAT_ETE
----------------
pratlucas wrote:

The output for `--print-enbled-extensions` was implemented using the following format:
```
Extensions enabled for the given AArch64 target

    Architecture Feature(s)                                Description
    FEAT_ETE                                               Enable Embedded Trace Extension
```
I chose not to include the `+foo` values in the output mostly because not all of the extensions are exposed via `-march`/`-mcpu` and the implications between them are not very clear. I'm happy to add these on a extra column, though, if you think there's value to it.

https://github.com/llvm/llvm-project/pull/95805