[clang] [CIR] Add if statement support (PR #134333)

[Andy Kaylor via cfe-commits]

================
@@ -316,6 +316,106 @@ void CIRGenFunction::emitIgnoredExpr(const Expr *e) {
   emitLValue(e);
 }
 
+/// Emit an `if` on a boolean condition, filling `then` and `else` into
+/// appropriated regions.
+mlir::LogicalResult CIRGenFunction::emitIfOnBoolExpr(const Expr *cond,
+                                                     const Stmt *thenS,
+                                                     const Stmt *elseS) {
+  // Attempt to be more accurate as possible with IfOp location, generate
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andykaylor wrote:

```suggestion
  // Attempt to be as accurate as possible with IfOp location, generate
```

https://github.com/llvm/llvm-project/pull/134333