[Support] Remove LLVM_ATTRIBUTE_NORETURN

[gAlfonso-bit]

Summary

Code should use C++11 [[noreturn]] or C11 _Noreturn instead.

[gAlfonso-bit]

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[mclow.lists]

I would like to see you undo all the formatting changes.
They are not germane for this patch, and (IMHO) reduce the readability of the code.

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[mclow.lists]

In D106899#2908395, @gAlfonso-bit wrote:

Done!

Thank you. That's *much* easier to review.

[mclow.lists]

I am not an approver for LLVM, but this LGTM.

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

[[noreturn]] is C++11.
In Oct 2016, the minimum compiler requirement was raised to GCC 4.8/MSVC 2015.
We can use [[noreturn]] since then.

I migrated lld/. I will watch the build bots and migrate llvm/

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

I migrated all llvm/ files. You need to remove them from the patch.

It is a good idea to drop the macro definition in llvm/include/llvm/Support/Compiler.h separately.

It makes it easy to bring back the definition if some important downstream users want extended time for migration.
(Note: the policy is that downstream is on their own. Our thinking of this is kindness, not an obligation of llvm-project.)
For example, swift is using LLVM_ATTRIBUTE_NORETURN.
(I researched a bit: LLVM_ATTRIBUTE_NORETURN is not common in downstream projects.)

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

Drop llvm/include/llvm/Support/Compiler.h change.

[gAlfonso-bit]

Removed Compiler.h changes

[gAlfonso-bit]

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[gAlfonso-bit]

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[gAlfonso-bit]

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[MaskRay]

In D106899#2913925, @gAlfonso-bit wrote:

Still not passing (what is going on?)

If you click a harbomaster URI, sometimes the builds are good

x64 debian passed
x64 windows passed

and sometimes there may be failures apparently unrelated to your patch.
Some discretion is needed.

I ended up making the refactoring by myself. Your change included some whole-file clang-format formatting which wasn't suitable.
I usually run git diff -U0 --no-color 'HEAD^' | clang/tools/clang-format/clang-format-diff.py -i -p1 to only format related lines.

[gAlfonso-bit]

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llvm/include/llvm/Support/Compiler.h

 #define LLVM_ATTRIBUTE_ALWAYS_INLINE inline
 #endif
 
-#ifdef __GNUC__
+// C++14 and up has [[noreturn]]
+#if defined(__cplusplus) && __cplusplus > 201300 &&                            \
+    LLVM_HAS_CPP_ATTRIBUTE(noreturn)
+#define LLVM_ATTRIBUTE_NORETURN [[noreturn]]
+// C11 and up has _Noreturn
+#elif !defined(__cplusplus) && __STDC_VERSION__ > 201112L
+#define LLVM_ATTRIBUTE_NORETURN _Noreturn
+#elif defined(__GNUC__) || __has_attribute(noreturn)
 #define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
 #elif defined(_MSC_VER)
 #define LLVM_ATTRIBUTE_NORETURN __declspec(noreturn)