[CIR] Fix for missing side effects during null pointer initialization #1547
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When a pointer variable is initialized with a null pointer, the AST contains a NullToPointer cast. If we just emit a null pointer of the correct type, we will miss any side effects that occur in the initializer. This change adds code to emit the initializer expression if it is not a simple constant. This results in an extra null pointer constant being emitted when the expression has side effects, but the constant emitted while visiting the expression does not have the correct type, so the alternative would be to capture the emitted constant and bitcast it to the correct type. An extra constant seems less intrusive than an unnecessary bitcast.
andykaylor requested review from bcardosolopes, dkolsen-pgi, erichkeane and lanza 
| Thanks to @dkolsen-pgi for suggesting the test case to introduce side effects in the initializer! |
terapines-osc-cir pushed a commit to Terapines/clangir that referenced this pull request Sep 2, 2025
…llvm#1547) When a pointer variable is initialized with a null pointer, the AST contains a NullToPointer cast. If we just emit a null pointer of the correct type, we will miss any side effects that occur in the initializer. This change adds code to emit the initializer expression if it is not a simple constant. This results in an extra null pointer constant being emitted when the expression has side effects, but the constant emitted while visiting the expression does not have the correct type, so the alternative would be to capture the emitted constant and bitcast it to the correct type. An extra constant seems less intrusive than an unnecessary bitcast.
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When a pointer variable is initialized with a null pointer, the AST contains a NullToPointer cast. If we just emit a null pointer of the correct type, we will miss any side effects that occur in the initializer. This change adds code to emit the initializer expression if it is not a simple constant.
This results in an extra null pointer constant being emitted when the expression has side effects, but the constant emitted while visiting the expression does not have the correct type, so the alternative would be to capture the emitted constant and bitcast it to the correct type. An extra constant seems less intrusive than an unnecessary bitcast.