[CodeGenPrep]No negative cost in the ExtLd promotion

Summary: This change prevent the signed value of cost from being negative as the value is passed as an unsigned argument.

Reviewers: mcrosier, jmolloy, qcolombet, javed.absar

Reviewed By: mcrosier, qcolombet

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28871

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293307 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed