[Backport to 16][OpaquePointers][LLVM->SPIRV] Cast the GEP base pointer to source type upon mismatch (#3255) #3263
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…er to source type upon mismatch (KhronosGroup#3255) The source element type used in a GEP may differ from the actual type of the pointer operand (e.g., ptr i8 vs. ptr [N x T]). This mismatch can lead to incorrect address computations during translation to SPIR-V of GEP used in constexpr context, which requires that pointer types match the type of the object being accessed. This patch inserts an explicit bitcast to convert the GEP pointer operand to the expected type, derived from the GEP’s source element type, before emitting an PtrAccessChain. This ensures the resulting SPIR-V instruction has a correctly typed base pointer and produces valid indexing behavior. For example: Before this change, the following GEP was translated incorrectly: getelementptr(i8, ptr addrspace(1) @a_var, i64 2) Whereas this nearly equivalent GEP was handled correctly: getelementptr inbounds ([2 x i8], ptr @a_var, i64 0, i64 1) Previously, the first form was incorrectly interpreted as: getelementptr inbounds ([2 x i8], ptr @a_var, i64 0, i64 2)
MrSidims
approved these changes
Jul 10, 2025
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The source element type used in a GEP may differ from the actual type of the pointer operand (e.g., ptr i8 vs. ptr [N x T]). This mismatch can lead to incorrect address computations during translation to SPIR-V of GEP used in constexpr context, which requires that pointer types match the type of the object being accessed.
This patch inserts an explicit bitcast to convert the GEP pointer operand to the expected type, derived from the GEP’s source element type, before emitting an PtrAccessChain.
This ensures the resulting SPIR-V instruction has a correctly typed base pointer and produces valid indexing behavior.
For example:
Before this change, the following GEP was translated incorrectly: getelementptr(i8, ptr addrspace(1) @a_var, i64 2)
Whereas this nearly equivalent GEP was handled correctly: getelementptr inbounds ([2 x i8], ptr @a_var, i64 0, i64 1)
Previously, the first form was incorrectly interpreted as: getelementptr inbounds ([2 x i8], ptr @a_var, i64 0, i64 2)