Summary:
"-fmerge-all-constants" is a non-conforming optimization and should not
be the default. It is also causing miscompiles when building Linux
Kernel (https://lkml.org/lkml/2018/3/20/872).
Fixes PR18538.
Reviewers: rjmccall, rsmith, chandlerc
Reviewed By: rsmith, chandlerc
Subscribers: srhines, cfe-commits
Differential Revision: https://reviews.llvm.org/D45289
llvm-svn: 329300
Summary:
This change avoids the overhead of storing, and later crawling,
an initializer list of all zeros for arrays. When LLVM
visits this (llvm/IR/Constants.cpp) ConstantArray::getImpl()
it will scan the list looking for an array of all zero.
We can avoid the store, and short-cut the scan, by detecting
all zeros when clang builds-up the initialization representation.
This was brought to my attention when investigating PR36030
Reviewers: majnemer, rjmccall
Reviewed By: rjmccall
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D42549
llvm-svn: 324776
Manoj Gupta