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[MachineLICM] A command-line option to hoist even cheap instructions

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Add a command-line option to enable hoisting even cheap instructions (in
low-register-pressure situations). This is turned off by default, but has
proved useful for testing purposes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225470 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2015-01-08 22:10:48 +00:00
parent 089a4ba180
commit 9d1500e68f
1 changed files with 6 additions and 1 deletions
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7
lib/CodeGen/MachineLICM.cpp
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@ -49,6 +49,11 @@ AvoidSpeculation("avoid-speculation",
cl::desc("MachineLICM should avoid speculation"),
cl::init(true), cl::Hidden);
static cl::opt<bool>
HoistCheapInsts("hoist-cheap-insts",
cl::desc("MachineLICM should hoist even cheap instructions"),
cl::init(false), cl::Hidden);
STATISTIC(NumHoisted,
"Number of machine instructions hoisted out of loops");
STATISTIC(NumLowRP,
@ -1075,7 +1080,7 @@ bool MachineLICM::CanCauseHighRegPressure(DenseMap<unsigned, int> &Cost,
// Don't hoist cheap instructions if they would increase register pressure,
// even if we're under the limit.
if (CheapInstr)
if (CheapInstr && !HoistCheapInsts)
return true;
for (unsigned i = BackTrace.size(); i != 0; --i) {