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[InstCombine] Add a flag to disable LowerDbgDeclare

Description

[InstCombine] Add a flag to disable LowerDbgDeclare

Summary:
This should improve optimized debug info for address-taken variables at
the cost of inaccurate debug info in some situations.

We patched this into clang and deployed this change to Chromium
developers, and this significantly improved debuggability of optimized
code. The long-term solution to PR34136 seems more and more like it's
going to take a while, so I would like to commit this change under a
flag so that it can be used as a stop-gap measure.

This flag should really help so for C++ aggregates like std::string and
std::vector, which are typically address-taken, even after inlining, and
cannot be SROA-ed.

Reviewers: aprantl, dblaikie, probinson, dberlin

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D36596

Details

Committed
rnkSep 12 2017, 6:43 PM
Differential Revision
D36596: [InstCombine] Add a flag to disable LowerDbgDeclare
Parents
rL313107: Add native_recip(x) as ((1)/(x))
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