[clang] [CIR] Add support for null checks with operator delete (PR #185987)

[Erich Keane via cfe-commits]

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@@ -1201,10 +1196,21 @@ void CIRGenFunction::emitCXXDeleteExpr(const CXXDeleteExpr *e) {
   // unconditionally perform the operator delete call in that case. For now, we
   // assume that deleted pointers are null rarely enough that it's better to
   // keep the branch. This might be worth revisiting for a -O0 code size win.
-  //
-  // CIR note: emit the code size friendly by default for now, such as mentioned
-  // in `emitObjectDelete`.
   assert(!cir::MissingFeatures::emitNullCheckForDeleteCalls());
+  cir::YieldOp thenYield;
+  mlir::Value notNull = builder.createPtrNotNull(ptr.getPointer());
+  cir::IfOp::create(builder, getLoc(e->getExprLoc()), notNull,
+                    /*withElseRegion=*/false,
+                    /*thenBuilder=*/
+                    [&](mlir::OpBuilder &b, mlir::Location loc) {
+                      thenYield = builder.createYield(loc);
+                    });
+
+  // Emit the rest of the CIR inside the if-op's then region, but restore the
+  // insertion point to the point after the if when this function returns.
+  mlir::OpBuilder::InsertionGuard guard(builder);
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erichkeane wrote:

Ah, huh.... I kinda hate those too :)  Less motivated to change here then, I'd suspect it would be cleaner/less awkward to change them all, but that can be done another day.

https://github.com/llvm/llvm-project/pull/185987