[CIR][Lowering] Fix BrCond Lowering

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -612,12 +612,18 @@ class CIRBrCondOpLowering
                   mlir::ConversionPatternRewriter &rewriter) const override {
     mlir::Value i1Condition;
 
+    auto hasOneUse = false;
+
+    if (auto defOp = brOp.getCond().getDefiningOp())
+      hasOneUse = defOp->getResult(0).hasOneUse();
+
     if (auto defOp = adaptor.getCond().getDefiningOp()) {
       if (auto zext = dyn_cast<mlir::LLVM::ZExtOp>(defOp)) {
         if (zext->use_empty() &&
             zext->getOperand(0).getType() == rewriter.getI1Type()) {
           i1Condition = zext->getOperand(0);
-          rewriter.eraseOp(zext);
+          if (hasOneUse)
+            rewriter.eraseOp(zext);
         }
       }
     }

clang/test/CIR/Lowering/brcond.cir

@@ -0,0 +1,43 @@
+// RUN: cir-opt %s -cir-to-llvm | FileCheck %s -check-prefix=MLIR
+// RUN: cir-translate %s -cir-to-llvmir | FileCheck %s -check-prefix=LLVM
+
+!s32i = !cir.int<s, 32>
+#fn_attr = #cir<extra({inline = #cir.inline<no>, nothrow = #cir.nothrow, optnone = #cir.optnone})>
+module { cir.func no_proto  @test() -> !cir.bool extra(#fn_attr) {
+    %0 = cir.const #cir.int<0> : !s32i 
+    %1 = cir.cast(int_to_bool, %0 : !s32i), !cir.bool 
+    cir.br ^bb1 
+  ^bb1:
+    cir.brcond %1 ^bb2, ^bb3 
+  ^bb2:
+    cir.return %1 : !cir.bool 
+  ^bb3:
+    cir.br ^bb4 
+  ^bb4:
+    cir.return %1 : !cir.bool 
+  } 
+}
+
+// MLIR:         {{.*}} = llvm.mlir.constant(0 : i32) : i32
+// MLIR-NEXT:    {{.*}} = llvm.mlir.constant(0 : i32) : i32
+// MLIR-NEXT:    {{.*}} = llvm.icmp "ne" {{.*}}, {{.*}} : i32
+// MLIR-NEXT:    {{.*}} = llvm.zext {{.*}} : i1 to i8
+// MLIR-NEXT:    llvm.br ^bb1
+// MLIR-NEXT:  ^bb1:
+// MLIR-NEXT:    llvm.cond_br {{.*}}, ^bb2, ^bb3
+// MLIR-NEXT:  ^bb2:
+// MLIR-NEXT:    llvm.return {{.*}} : i8
+// MLIR-NEXT:  ^bb3:
+// MLIR-NEXT:    llvm.br ^bb4
+// MLIR-NEXT:  ^bb4:
+// MLIR-NEXT:    llvm.return {{.*}} : i8
+
+// LLVM: br label {{.*}}
+// LLVM: 1:
+// LLVM: br i1 false, label {{.*}}, label {{.*}}
+// LLVM: 2:
+// LLVM:  ret i8 0
+// LLVM: 3:
+// LLVM:  br label {{.*}}
+// LLVM: 4:
+// LLVM:  ret i8 0