[flang] [llvm] [Pipeline] Add IPSCCPPass at O3 to fix function specialization phase ordering (PR #201543)

[via llvm-commits]

anoopkg6 wrote:

Since this PR was submitted, [#207732](https://github.com/llvm/llvm-project/pull/207732) ([flang] Propagate INTENT(IN) dummy arguments as readonly) was merged on July 14. This patch enables FuncSpec in the first IPSCCP pass by satisfying the onlyReadsMemory() check in promoteConstantStackValues. This affects the performance numbers quoted in the original description. Updated analysis on interaction of two patches to follow.

https://github.com/llvm/llvm-project/pull/201543