[llvm] [NVPTX] Improve support for rsqrt.approx (PR #89417)

[Artem Belevich via llvm-commits]

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@@ -30,6 +30,10 @@ using namespace llvm;
 #define DEBUG_TYPE "nvptx-isel"
 #define PASS_NAME "NVPTX DAG->DAG Pattern Instruction Selection"
 
+static cl::opt<bool>
+    DisableRsqrtOpt("nvptx-disable-rsqrt-opt", cl::init(false), cl::Hidden,
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Artem-B wrote:

Also, a nit on the option name. Disabling a "disable-something" knob always strikes me as odd.  Can we make it a positive control? E.g. `-nvptx-approx-rsqrt` ? 

Naming is hard. :-/ 

https://github.com/llvm/llvm-project/pull/89417