[llvm] [SPIR-V] Strip convergence intrinsics before ISel (PR #75948)

[Nathan Gauër via llvm-commits]

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@@ -12,6 +12,8 @@
 // restore correct SPIR-V types of function arguments and return values.
 // This pass also substitutes some llvm intrinsic calls with calls to newly
 // generated functions (as the Khronos LLVM/SPIR-V Translator does).
+// This pass also trims convergence intrinsics as those were only useful when
+// modifying the CFG during IR passes.
 //
 // NOTE: this pass is a module-level one due to the necessity to modify
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Keenuts wrote:

Done, forced pushed for rebase and since this means mostly a rewrite

https://github.com/llvm/llvm-project/pull/75948