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[StackIR] Emit unreachable for unwritable insts - #9283
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BinaryInstWriter emits an unreachable instruction when an expression has an unwritable heap type immediate or is a StringNew or StringEncode with a null-typed array operand, but StackIRGenerator::emit previously emitted a normal Basic StackInst for those expressions. Include StringNew and StringEncode with null-typed array operands in Properties::hasUnwritableTypeImmediate and emit unreachable in StackIRGenerator::emit when it returns true so StackIROptimizer and PrintStackIR see the unreachable instruction that will be written to the binary. Also fix BinaryInstWriter::visitStringEncode to check whether curr->array (rather than curr->str) has a null type.
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This pull request updates the handling of string array operations with null-typed array operands to ensure they are correctly identified as having unwritable type immediates. Specifically, it updates hasUnwritableTypeImmediate in src/ir/properties.h to check StringNew and StringEncode expressions, fixes a type check in BinaryInstWriter::visitStringEncode, and ensures StackIRGenerator::emit emits unreachable for these expressions. Test cases are also updated and added to verify the behavior. The review feedback suggests adding defensive null checks for sn->ref and se->array in hasUnwritableTypeImmediate to prevent potential null pointer dereferences.
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aheejin
approved these changes
Oct 20, 2026
This reverts commit 972d469.
…nreachable # Conflicts: # src/wasm/wasm-stack.cpp
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BinaryInstWriter emits an unreachable instruction when an expression has an unwritable heap type immediate or is a StringNew or StringEncode with a null-typed array operand, but StackIRGenerator::emit previously emitted a normal Basic StackInst for those expressions. Include StringNew and StringEncode with null-typed array operands in Properties::hasUnwritableTypeImmediate and emit unreachable in StackIRGenerator::emit when it returns true so StackIROptimizer and PrintStackIR see the unreachable instruction that will be written to the binary.
Also fix BinaryInstWriter::visitStringEncode to check whether curr->array (rather than curr->str) has a null type.