[AArch64] Disable __ARM_FEATURE_SVE without ACLE.

[sdesmalen]

Summary

The Arm C Language Extensions for SVE document specifies that
__ARM_FEATURE_SVE should be set when the compiler supports SVE and
implements all the extensions described in the document.

This is currently not yet the case, so the feature should be disabled
until the compiler can provide all the extensions as described.

[rengolin]

I understand (and agree with) the reasoning of this patch, but wouldn't this also make it harder to test the current behaviour?

I mean, LLVM doesn't support officially SVE entirely, so there's no point in expecting anything to work for now. What is the coverage of the current ACLE implementation in Clang/LLVM?

If we already have the most used ones, how about adding a warning that SVE support is not complete, YMMV, etc. instead?

[sdesmalen]

Thanks, I see your argument for having the feature enabled even when the ACLE is still partially supported. At the moment however, LLVM still only support the assembler/disassembler and inline asm.
We'll be working to add support for the ACLE soon, but for now having the flag enabled sets the wrong expectations.

[rengolin]

I see, makes sense. LGTM, thanks!

cfe/trunk/lib/Basic/Targets/AArch64.cpp

void AArch64TargetInfo::getTargetDefines(const LangOptions &Opts,
   Builder.defineMacro("__ARM_SIZEOF_MINIMAL_ENUM", Opts.ShortEnums ? "1" : "4");
 
   if (FPU & NeonMode) {
     Builder.defineMacro("__ARM_NEON", "1");
     // 64-bit NEON supports half, single and double precision operations.
     Builder.defineMacro("__ARM_NEON_FP", "0xE");
   }
 
-  if (FPU & SveMode)
-    Builder.defineMacro("__ARM_FEATURE_SVE", "1");
-
   if (HasCRC)
     Builder.defineMacro("__ARM_FEATURE_CRC32", "1");
 
   if (HasCrypto)
     Builder.defineMacro("__ARM_FEATURE_CRYPTO", "1");
 
   if (HasUnaligned)
     Builder.defineMacro("__ARM_FEATURE_UNALIGNED", "1");

cfe/trunk/test/Preprocessor/aarch64-target-features.c

 
 // RUN: %clang -target aarch64 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-GENERIC %s
 // RUN: %clang -target aarch64 -march=armv8-a -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-GENERIC %s
 // CHECK-GENERIC: "-cc1"{{.*}} "-triple" "aarch64{{.*}}" "-target-feature" "+neon"
 
 // RUN: %clang -target aarch64 -mtune=cyclone -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-MTUNE-CYCLONE %s
 
 // RUN: %clang -target aarch64-none-linux-gnu -march=armv8-a+sve -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-SVE %s
-// CHECK-SVE: __ARM_FEATURE_SVE 1
+// CHECK-SVE-NOT: __ARM_FEATURE_SVE 1
 
 // RUN: %clang -target aarch64-none-linux-gnu -march=armv8.2a+dotprod -x c -E -dM %s -o - | FileCheck --check-prefix=CHECK-DOTPROD %s
 // CHECK-DOTPROD: __ARM_FEATURE_DOTPROD 1
 
 // On ARMv8.2-A and above, +fp16fml implies +fp16.
 // On ARMv8.4-A and above, +fp16 implies +fp16fml.
 // RUN: %clang -target aarch64-none-linux-gnueabi -march=armv8.2-a+nofp16fml+fp16 -x c -E -dM %s -o - | FileCheck -match-full-lines --check-prefix=CHECK-FULLFP16-NOFML --check-prefix=CHECK-FULLFP16-VECTOR-SCALAR %s
 // RUN: %clang -target aarch64-none-linux-gnueabi -march=armv8.2-a+nofp16+fp16fml -x c -E -dM %s -o - | FileCheck -match-full-lines --check-prefix=CHECK-FULLFP16-FML --check-prefix=CHECK-FULLFP16-VECTOR-SCALAR %s