[clang] [llvm] [clang][HLSL][SPRI-V] Add convergence intrinsics (PR #80680)

[Matt Arsenault via cfe-commits]

Nathan =?utf-8?q?Gauër?= <brioche at google.com>,
Nathan =?utf-8?q?Gauër?= <brioche at google.com>,
Nathan =?utf-8?q?Gauër?= <brioche at google.com>,
Nathan =?utf-8?q?Gauër?= <brioche at google.com>,
Nathan =?utf-8?q?Gauër?= <brioche at google.com>,
Nathan =?utf-8?q?Gauër?= <brioche at google.com>
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In-Reply-To: <llvm.org/llvm/llvm-project/pull/80680 at github.com>


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@@ -1295,11 +1295,13 @@ double4 trunc(double4);
 /// true, across all active lanes in the current wave.
 _HLSL_AVAILABILITY(shadermodel, 6.0)
 _HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_active_count_bits)
+__attribute__((convergent))
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arsenm wrote:

Convergence requires all transitive callers to also be convergent. No real code is going to do this. The existence of convergence operations means you have a convergent language and must optimize to known-not-convergent 

https://github.com/llvm/llvm-project/pull/80680