[clang][AArch64] test -cc1 -print-enabled-extensions

[tmatheson-arm]

This adds tests that document how -cc1 and -print-enabled-extensions interact. The current behaviour looks wrong, and is caused by the fact that --print-enabled-extensions uses the MC subtarget feature API to determine the list of extensions to print, whereas the frontend uses the TargetParser API. The latter does no dependency expansion for the -target-feature flags but the MC API does.

This doesn't fix anything but at least it documents the current behaviour, and will serve as a pre-commit test for any future fixes.

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

@llvm/pr-subscribers-clang

Author: Tomas Matheson (tmatheson-arm)

Changes

This adds tests that document how -cc1 and -print-enabled-extensions interact. The current behaviour looks wrong, and is caused by the fact that --print-enabled-extensions uses the MC subtarget feature API to determine the list of extensions to print, whereas the frontend uses the TargetParser API. The latter does no dependency expansion for the -target-feature flags but the MC API does.

This doesn't fix anything but at least it documents the current behaviour, and will serve as a pre-commit test for any future fixes.

---

Full diff: https://github.com/llvm/llvm-project/pull/143570.diff

1 Files Affected:

• (added) clang/test/Frontend/aarch64-print-enabled-extensions-cc1.c (+139)

diff --git a/clang/test/Frontend/aarch64-print-enabled-extensions-cc1.c b/clang/test/Frontend/aarch64-print-enabled-extensions-cc1.c
new file mode 100644
index 0000000000000..5d65fdafaa251
--- /dev/null
+++ b/clang/test/Frontend/aarch64-print-enabled-extensions-cc1.c
@@ -0,0 +1,139 @@
+// Test how -cc1 -target-feature interacts with -print-enabled-extensions.
+// The current behaviour does not look correct, since dependent features are
+// removed from the printed list when one of their dependencies are disabled,
+// but they are actually still enabled during compilation, and then actually
+// disabled for parsing assembly.
+
+// REQUIRES: aarch64-registered-target
+
+// Behaviour with two positive features.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +neon -target-feature +sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=POS_ONLY
+
+// Negative -target-feature disables the extension but keeps any dependencies of it (FEAT_FP16).
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +neon -target-feature +sve -target-feature -sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=POS_NEG
+
+// Disabling then re-enabling a feature is the same as never disabling it.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +neon -target-feature -sve -target-feature +sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=POS_ONLY
+
+// Disabling then re-enabling a feature is the same as never disabling it.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +neon -target-feature +sve -target-feature -sve -target-feature +sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=POS_ONLY
+
+// Only disabling it is the same as never having enabled it.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +neon \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=NEG_ONLY
+
+// Only disabling it is the same as never having enabled it.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +neon -target-feature -sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=NEG_ONLY
+
+// Disabling a dependency (after enabling the dependent) appears to disable the dependent feature.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +sve2 -target-feature -sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=DISABLE_DEP
+
+// Disabling a dependency before enabling the dependent appears to have no effect.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature -sve -target-feature +sve2 \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=DISABLE_DEP2
+
+// Disabling a dependency before enabling the dependent appears to have no effect.
+// RUN: %clang_cc1 -triple aarch64-unknown-linux-gnu -print-enabled-extensions \
+// RUN:     -target-feature +sve2 \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=DISABLE_DEP2
+
+// Driver --print-enabled-extensions indicates that negative -target-features disable dependent features.
+// RUN: %clang --target=aarch64 -march=armv8-a+sve2 --print-enabled-extensions \
+// RUN:     -Xclang -target-feature -Xclang -sve \
+// RUN:     | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s --check-prefix=DISABLE_VIA_XCLANG
+
+// However, sve2 is actually enabled in clang but disabled for MC.
+// RUN: %clang --target=aarch64 -march=armv8-a+sve2 -c %s \
+// RUN:     -Xclang -target-feature -Xclang -sve \
+// RUN:     -Xclang -verify -Xclang -verify-ignore-unexpected=note
+
+
+// POS_ONLY: Extensions enabled for the given AArch64 target
+// POS_ONLY-EMPTY:
+// POS_ONLY-NEXT:     Architecture Feature(s)                                Description
+// POS_ONLY-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// POS_ONLY-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// POS_ONLY-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// POS_ONLY-NEXT:     FEAT_FP16                                              Enable half-precision floating-point data processing
+// POS_ONLY-NEXT:     FEAT_SVE                                               Enable Scalable Vector Extension (SVE) instructions
+// POS_ONLY-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+// POS_NEG: Extensions enabled for the given AArch64 target
+// POS_NEG-EMPTY:
+// POS_NEG-NEXT:     Architecture Feature(s)                                Description
+// POS_NEG-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// POS_NEG-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// POS_NEG-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// POS_NEG-NEXT:     FEAT_FP16                                              Enable half-precision floating-point data processing
+// POS_NEG-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+// NEG_POS: Extensions enabled for the given AArch64 target
+// NEG_POS-EMPTY:
+// NEG_POS-NEXT:     Architecture Feature(s)                                Description
+// NEG_POS-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// NEG_POS-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// NEG_POS-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// NEG_POS-NEXT:     FEAT_FP16                                              Enable half-precision floating-point data processing
+// NEG_POS-NEXT:     FEAT_SVE                                               Enable Scalable Vector Extension (SVE) instructions
+// NEG_POS-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+// NEG_ONLY: Extensions enabled for the given AArch64 target
+// NEG_ONLY-EMPTY:
+// NEG_ONLY-NEXT:     Architecture Feature(s)                                Description
+// NEG_ONLY-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// NEG_ONLY-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// NEG_ONLY-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// NEG_ONLY-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+// DISABLE_DEP: Extensions enabled for the given AArch64 target
+// DISABLE_DEP-EMPTY: 
+// DISABLE_DEP-NEXT:     Architecture Feature(s)                                Description
+// DISABLE_DEP-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// DISABLE_DEP-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// DISABLE_DEP-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// DISABLE_DEP-NEXT:     FEAT_FP16                                              Enable half-precision floating-point data processing
+// DISABLE_DEP-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+// DISABLE_DEP2: Extensions enabled for the given AArch64 target
+// DISABLE_DEP2-EMPTY: 
+// DISABLE_DEP2-NEXT:     Architecture Feature(s)                                Description
+// DISABLE_DEP2-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// DISABLE_DEP2-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// DISABLE_DEP2-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// DISABLE_DEP2-NEXT:     FEAT_FP16                                              Enable half-precision floating-point data processing
+// DISABLE_DEP2-NEXT:     FEAT_SVE                                               Enable Scalable Vector Extension (SVE) instructions
+// DISABLE_DEP2-NEXT:     FEAT_SVE2                                              Enable Scalable Vector Extension 2 (SVE2) instructions
+// DISABLE_DEP2-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+// DISABLE_VIA_XCLANG: Extensions enabled for the given AArch64 target
+// DISABLE_VIA_XCLANG-EMPTY: 
+// DISABLE_VIA_XCLANG-NEXT:     Architecture Feature(s)                                Description
+// DISABLE_VIA_XCLANG-NEXT:     FEAT_AdvSIMD                                           Enable Advanced SIMD instructions
+// DISABLE_VIA_XCLANG-NEXT:     FEAT_ETE                                               Enable Embedded Trace Extension
+// DISABLE_VIA_XCLANG-NEXT:     FEAT_FP                                                Enable Armv8.0-A Floating Point Extensions
+// DISABLE_VIA_XCLANG-NEXT:     FEAT_FP16                                              Enable half-precision floating-point data processing
+// DISABLE_VIA_XCLANG-NEXT:     FEAT_TRBE                                              Enable Trace Buffer Extension
+
+#if __ARM_FEATURE_SVE2
+#warning "SVE2 is enabled"
+// expected-warning@-1 {{SVE2 is enabled}}
+#endif
+
+void fn_that_requires_sve2() {
+    __asm__("ldnt1sh z0.s, p0/z, [z1.s]");
+    // expected-error@-1 {{instruction requires: sve2}}
+}

[labrinea]

We can debate on what the sensible behavior ought to be, but I agree having a test in place to show the current behavior is a good idea. Thanks for writing one.