[PATCH] D52852: [WebAssembly] __builtin_wasm_extract_lane_* builtins

[Craig Topper via Phabricator via cfe-commits]

craig.topper added inline comments.


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Comment at: include/clang/Basic/BuiltinsWebAssembly.def:46
+BUILTIN(__builtin_wasm_extract_lane_s_i16x8, "iV8sIi", "ncV:128:")
+BUILTIN(__builtin_wasm_extract_lane_u_i16x8, "iV8sIi", "ncV:128:")
+BUILTIN(__builtin_wasm_extract_lane_i32x4, "iV4iIi", "ncV:128:")
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aheejin wrote:
> - I guess the return types should be the same as its element type, because we are translating to not wasm but LLVM IR instructions and `extractelement`'s return type and element type are the same.
> - What does `I` mean in the second argument? The instruction says it is required for constant folding. How is the generated IR different if we use it?
The I makes Sema ensure it is a Integer Constant Expression.


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Comment at: lib/CodeGen/CGBuiltin.cpp:12433
+    Value *Vec = EmitScalarExpr(E->getArg(0));
+    Value *Lane = EmitScalarExpr(E->getArg(1));
+    Value *Extract = Builder.CreateExtractElement(Vec, Lane);
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I believe you need to use isIntegerConstantExpr to force clang to really evaluate it as a constant integer. if its a more complicated expression.


Repository:
  rC Clang

https://reviews.llvm.org/D52852