[llvm] [ConstantTime][LLVM] Add llvm.ct.select intrinsic with generic SelectionDAG lowering (PR #166702)

[Julius Alexandre via llvm-commits]

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@@ -476,9 +476,10 @@ class LLVM_ABI TargetLoweringBase {
   MachineMemOperand::Flags
   getVPIntrinsicMemOperandFlags(const VPIntrinsic &VPIntrin) const;
 
-  virtual bool isSelectSupported(SelectSupportKind /*kind*/) const {
-    return true;
-  }
+  virtual bool isSelectSupported(SelectSupportKind kind) const { return true; }
+
+  /// Return true if the target has custom lowering for constant-time select.
+  virtual bool isCtSelectSupported(EVT VT) const { return false; }
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wizardengineer wrote:

I removed it completely and relied on `isOperationLegalOrCustom` instead.

https://github.com/llvm/llvm-project/pull/166702