[llvm] [X86] LowerAsmOperandForConstraint - ensure we treat L constraint immediates as signed constants (PR #171098)

[Simon Pilgrim via llvm-commits]

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RKSimon wrote:

Yes - for completeness it should be, although it won't currently assert as we're sign extending a i32 to i64 - so the getTargetConstant(uint64_t, SDLoc, MVT::i64) type is guaranteed to be re-presentable as i64.

https://github.com/llvm/llvm-project/pull/171098