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Currently the describeLoadedValue() hook is assumed to describe the value of the instruction's first explicit define. The hook will not be called for instructions with more than one explicit define. This commit adds a register parameter to the describeLoadedValue() hook, and invokes the hook for all registers in the worklist. This will allow us to for example describe instructions which produce more than two parameters' values; e.g. Hexagon's various combine instructions. This also fixes a case in our downstream target where we may pass smaller parameters in the high part of a register. If such a parameter's value is produced by a larger copy instruction, we can't describe the call site value using the super-register, and we instead need to know which sub-register that should be used. This also allows us to handle cases like this: $ebx = [...] $rdi = MOVSX64rr32 $ebx $esi = MOV32rr $edi CALL64pcrel32 @call The hook will first be invoked for the MOV32rr instruction, which will say that @call's second parameter (passed in $esi) is described by $edi. As $edi is not preserved it will be added to the worklist. When we get to the MOVSX64rr32 instruction, we need to describe two values; the sign-extended value of $ebx -> $rdi for the first parameter, and $ebx -> $edi for the second parameter, which is now possible. This commit modifies the dbgcall-site-lea-interpretation.mir test case. In the test case, the values of some 32-bit parameters were produced with LEA64r. Perhaps we can in general cases handle such by emitting expressions that AND out the lower 32-bits, but I have not been able to land in a case where a LEA64r is used for a 32-bit parameter instead of LEA64_32 from C code. I have not found a case where it would be useful to describe parameters using implicit defines, so in this patch the hook is still only invoked for explicit defines of forwarding registers.
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