[CIR][CodeGen][BugFix] don't place alloca before the label (#875)

This PR fixes the case, when a temporary var is used, and `alloca`
operation is inserted in the block start before the `label` operation.
Implementation: when we search for the `alloca` place in a block, we
take label operations into account as well.

Fix #870

---------

Co-authored-by: Bruno Cardoso Lopes <[email protected]>

Author: 2 people

clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h

@@ -538,14 +538,14 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
   // ----------------------
   //
   OpBuilder::InsertPoint getBestAllocaInsertPoint(mlir::Block *block) {
-    auto lastAlloca =
+    auto last =
         std::find_if(block->rbegin(), block->rend(), [](mlir::Operation &op) {
-          return mlir::isa<mlir::cir::AllocaOp>(&op);
+          return mlir::isa<mlir::cir::AllocaOp, mlir::cir::LabelOp>(&op);
         });
 
-    if (lastAlloca != block->rend())
+    if (last != block->rend())
       return OpBuilder::InsertPoint(block,
-                                    ++mlir::Block::iterator(&*lastAlloca));
+                                    ++mlir::Block::iterator(&*last));
     return OpBuilder::InsertPoint(block, block->begin());
   };
 

clang/test/CIR/CodeGen/goto.cpp

@@ -271,4 +271,20 @@ void flatLoopWithNoTerminatorInFront(int* ptr) {
 // CHECK:  ^bb[[#RETURN]]:
 // CHECK:    cir.return
 // CHECK:  }
-// CHECK:}
+// CHECK:}
+
+struct S {};
+struct S get();
+void bar(struct S);
+
+void foo() {
+  { 
+    label:      
+      bar(get());
+  }   
+}
+
+// NOFLAT: cir.func  @_Z3foov()
+// NOFLAT:   cir.scope {
+// NOFLAT:     cir.label "label"
+// NOFLAT:     %0 = cir.alloca !ty_S, !cir.ptr<!ty_S>, ["agg.tmp0"]