Commit Graph

3 Commits

Author SHA1 Message Date
Simon Dardis 230f453574 [CodeGenPrepare] Check that erased sunken address are not reused
CodeGenPrepare sinks address computations from one basic block to another
and attempts to reuse address computations that have already been sunk. If
the same address computation appears twice with the first instance as an
operand of a load whose result is an operand to a simplifable select,
CodeGenPrepare simplifies the select and recursively erases the now dead
instructions. CodeGenPrepare then attempts to use the erased address
computation for the second load.

Fix this by erasing the cached address value if it has zero uses before
looking for the address value in the sunken address map.

This partially resolves PR35209.

Thanks to Alexander Richardson for reporting the issue!

This fixed version relands r318032 which was reverted in r318049 due to
sanitizer buildbot failures.

Reviewers: john.brawn

Differential Revision: https://reviews.llvm.org/D39841

llvm-svn: 318956
2017-11-24 16:45:28 +00:00
Simon Dardis 8222160eb3 Revert "[CodeGenPrepare] Check that erased sunken address are not reused"
This reverts commit r318032. The test broke some sanitizer bots.

llvm-svn: 318049
2017-11-13 16:41:17 +00:00
Simon Dardis 8e2a5bd235 [CodeGenPrepare] Check that erased sunken address are not reused
CodeGenPrepare sinks address computations from one basic block to another
and attempts to reuse address computations that have already been sunk. If
the same address computation appears twice with the first instance as an
operand of a load whose result is an operand to a simplifable select,
CodeGenPrepare simplifies the select and recursively erases the now dead
instructions. CodeGenPrepare then attempts to use the erased address
computation for the second load.

Fix this by erasing the cached address value if it has zero uses before
looking for the address value in the sunken address map.

This partially resolves PR35209.

Thanks to Alexander Richardson for reporting the issue!

Reviewers: john.brawn

Differential Revision: https://reviews.llvm.org/D39841

llvm-svn: 318032
2017-11-13 11:47:21 +00:00