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

[David Spickett via cfe-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
----------------
DavidSpickett wrote:

I'm surprised that this doesn't show the name the user would use with `-march`, is that expected?

Since `--print-supported-extensions` shows it:
```
All available -march extensions for AArch64

    Name                Description
    aes                 Enable AES support (FEAT_AES, FEAT_PMULL)
```

And if I were comparing two command lines I might want to know what `+foo` I need to add to one to make it equivalent to the other.

Or I am misreading the output and the name is there already :)

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