On AMDGPU, alloca instructions have penalty that can
be avoided when SROA is applied after inlining.
This patch introduces the default implementation of
TargetTransformInfo::getCallerAllocaCost.
Reviewed By: mtrofin
Differential Revision: https://reviews.llvm.org/D149740
This change yields an additional 2% size reduction on an internal search
binary, and an additional 0.5% size reduction on fuchsia.
Differential Revision: https://reviews.llvm.org/D104751