[TableGen] CodeGenDAGPatterns::GenerateVariants - full caching of matching predicates

Further extension to D51035, this patch avoids all repeated predicates[] matching by caching as it collects the patterns that have multiple variants.

Saves around 25secs in debug builds of x86 -gen-dag-isel.

Differential Revision: https://reviews.llvm.org/D51839

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342467 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed