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| author | Chris Lattner <sabre@nondot.org> | 2010-04-05 22:14:48 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2010-04-05 22:14:48 +0000 |
| commit | adca6082812fa43d1ad4d76d305b80aaa0e8f0d4 (patch) | |
| tree | 40d91e262e071b303122fe1f27af5a1aeaf2dfe4 /llvm/lib/Transforms/Utils/DemoteRegToStack.cpp | |
| parent | 01fa5c3734d6bc44c498abe8c4410b00d1edad71 (diff) | |
| download | bcm5719-llvm-adca6082812fa43d1ad4d76d305b80aaa0e8f0d4.tar.gz bcm5719-llvm-adca6082812fa43d1ad4d76d305b80aaa0e8f0d4.zip | |
fix a really nasty bug that Evan was tracking in SCCP. When resolving
undefs in branches/switches, we have two cases: a branch on a literal
undef or a branch on a symbolic value which is undef. If we have a
literal undef, the code was correct: forcing it to a constant is the
right thing to do.
If we have a branch on a symbolic value that is undef, we should force
the symbolic value to a constant, which then makes the successor block
live. Forcing the condition of the branch to being a constant isn't
safe if later paths become live and the value becomes overdefined. This
is the case that 'forcedconstant' is designed to handle, so just use it.
This fixes rdar://7765019 but there is no good testcase for this, the
one I have is too insane to be useful in the future.
llvm-svn: 100478
Diffstat (limited to 'llvm/lib/Transforms/Utils/DemoteRegToStack.cpp')
0 files changed, 0 insertions, 0 deletions
