[clang] [CIR] Upstream lowering of conditional operators to TernaryOp (PR #138156)

[Erich Keane via cfe-commits]

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@@ -272,6 +272,22 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
     return createCast(loc, cir::CastKind::bitcast, src, newTy);
   }
 
+  // TODO(cir): the following function was introduced to keep in sync with LLVM
+  // codegen. CIR does not have "zext" operations. It should eventually be
+  // renamed or removed. For now, we just add whatever cast is required here.
+  mlir::Value createZExtOrBitCast(mlir::Location loc, mlir::Value src,
+                                  mlir::Type newTy) {
+    mlir::Type srcTy = src.getType();
+
+    if (srcTy == newTy)
+      return src;
+
+    if (mlir::isa<cir::BoolType>(srcTy) && mlir::isa<cir::IntType>(newTy))
+      return createBoolToInt(src, newTy);
+
+    llvm_unreachable("unhandled extension cast");
----------------
erichkeane wrote:

This doesn't seem like it should be an unreachable, right?  Perhaps an assert that the types are equal or its int-to-bool, but this unreachable seems odd?  also, what function in classic-codegen is this intended to mirror?  The only one I found was the `CastInst` one by the same name, and it doesn't seem to mirror its implementation much at all.

https://github.com/llvm/llvm-project/pull/138156