[clang] [llvm] [HLSL] Implement `rsqrt` intrinsic (PR #84820)

[Damyan Pepper via cfe-commits]

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@@ -0,0 +1,27 @@
+
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm -disable-llvm-passes -verify -verify-ignore-unexpected
+
+float test_too_few_arg() {
+  return __builtin_hlsl_elementwise_rsqrt();
+  // expected-error at -1 {{too few arguments to function call, expected 1, have 0}}
+}
+
+float2 test_too_many_arg(float2 p0) {
+  return __builtin_hlsl_elementwise_rsqrt(p0, p0);
+  // expected-error at -1 {{too many arguments to function call, expected 1, have 2}}
+}
+
+float builtin_bool_to_float_type_promotion(bool p1) {
+  return __builtin_hlsl_elementwise_rsqrt(p1);
+  // expected-error at -1 {{1st argument must be a vector, integer or floating point type (was 'bool')}}
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damyanp wrote:

"integer" - is this true?  I thought it only worked with things that were float-like.

https://github.com/llvm/llvm-project/pull/84820