Jesper Antonsson via llvm-dev
2016-Apr-21 14:32 UTC
[llvm-dev] opt function passes swallowed
Hi,
I've observed that FunctionPasses are not run when a specific argument order
is handed to opt. I.e. when I specify:
opt -O3 -float2int file.ll
... the FunctionPasses specified by populateFunctionPasses() are not run.
However, if I put the -O3 after all manually specified passes, then the
FunctionPasses are run:
opt -float2int -O3 file.ll
In the code (opt.cpp), we are explicitly checking the argument order (somewhere
around line 537 for me):
if (OptLevelO3 && OptLevelO3.getPosition() <
PassList.getPosition(i)) {
AddOptimizationPasses(Passes, *FPasses, 3, 0);
OptLevelO3 = false;
}
Note that we set OptLevelO3 to false above. Later, we run FPasses only if some
OptLevelO<n> is true:
if (OptLevelO1 || OptLevelO2 || OptLevelOs || OptLevelOz || OptLevelO3) {
FPasses->doInitialization();
for (Function &F : *M)
FPasses->run(F);
FPasses->doFinalization();
}
Thus FPasses are not run if -O<n> comes before any manually specified
passes in the argument list. Anyone knows if this is intentional and if so, why?
Regards,
Jesper
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