[mono] Always store to allocas in OP_LLVM_OUTARG_VT #64303
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OP_LLVM_OUTARG_VT will, for some argument passing conventions, create an alloca and mirror its source SSA value into this alloca. If such an OP_LLVM_OUTARG_VT is first encountered in a basic block that does not contain the definition of the SSA value being mirrored, then sibling basic blocks (e.g. a loop body that may sometimes be skipped) can use garbage data if they also have OP_LLVM_OUTARG_VT opcodes referring to the same SSA values. This commit works around this by unconditionally storing the source OP_LLVM_OUTARG_VT value into its associated alloca. The resulting IR would be a little easier to read if we eagerly stored to an alloca mirror exactly once at each value's definition, but that would require more work to implement.
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OP_LLVM_OUTARG_VT will, for some argument passing conventions, create an
alloca and mirror its source SSA value into this alloca. If such an
OP_LLVM_OUTARG_VT is first encountered in a basic block that does not
contain the definition of the SSA value being mirrored, then sibling
basic blocks (e.g. a loop body that may sometimes be skipped) can use
garbage data if they also have OP_LLVM_OUTARG_VT opcodes referring to
the same SSA values.
This commit works around this by unconditionally storing the source
OP_LLVM_OUTARG_VT value into its associated alloca. The resulting IR
would be a little easier to read if we eagerly stored to an alloca
mirror exactly once at each value's definition, but that would require
more work to implement.
Fixes JIT/SIMD/VectorExp_ro/VectorExp_ro. See #64179.