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Add comment explaining the alignment setting

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This commit is contained in:
Koakuma 2021-02-05 00:25:01 +07:00
parent e3e4af7271
commit d23dfdeab9
1 changed files with 6 additions and 0 deletions
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6
src/stage1/codegen.cpp
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@ -4161,6 +4161,12 @@ static LLVMValueRef gen_frame_size(CodeGen *g, LLVMValueRef fn_val) {
LLVMValueRef negative_one = LLVMConstInt(LLVMInt32Type(), -1, true);
LLVMValueRef prefix_ptr = LLVMBuildInBoundsGEP(g->builder, casted_fn_val, &negative_one, 1, "");
LLVMValueRef load_inst = LLVMBuildLoad(g->builder, prefix_ptr, "");
// Some architectures (e.g SPARCv9) has different alignment requirements between a
// function/usize pointer and also require all loads to be aligned.
// On those architectures, not explicitly setting the alignment will lead into @frameSize
// generating usize-aligned load instruction that could crash if the function pointer
// happens to be not usize-aligned.
LLVMSetAlignment(load_inst, 1);
return load_inst;
}