[libclc] [libclc] Move rsqrt to the CLC library (PR #129045)

[Matt Arsenault via cfe-commits]

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@@ -0,0 +1,4 @@
+__attribute__((weak)) _CLC_OVERLOAD _CLC_DEF __CLC_GENTYPE
+__clc_rsqrt(__CLC_GENTYPE val) {
+  return __CLC_FP_LIT(1.0) / __clc_sqrt(val);
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arsenm wrote:

For this to work as you want, probably needs to directly use the sqrt builtin (or really, we should enable fast contract throughout the entire library and disable it in the handful of locations that are not OK with it)

https://github.com/llvm/llvm-project/pull/129045