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MachineSink: make shouldSink a TII target hook

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Some targets may disagree on what they want sunk or not sunk,
so make this a target hook instead of hardcoded.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264799 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Fiona Glaser 2016-03-29 22:44:57 +00:00
parent d6dc9e03af
commit 513c245e44
2 changed files with 14 additions and 7 deletions
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12
include/llvm/Target/TargetInstrInfo.h
View File

@ -256,6 +256,18 @@ public:
return MI->isAsCheapAsAMove();
}
/// Return true if the instruction should be sunk by MachineSink.
///
/// MachineSink determines on its own whether the instruction is safe to sink;
/// this gives the target a hook to override the default behavior with regards
/// to which instructions should be sunk.
/// The default behavior is to not sink insert_subreg, subreg_to_reg, and
/// reg_sequence. These are meant to be close to the source to make it easier
/// to coalesce.
virtual bool shouldSink(const MachineInstr &MI) const {
return !MI.isInsertSubreg() && !MI.isSubregToReg() && !MI.isRegSequence();
}
/// Re-issue the specified 'original' instruction at the
/// specific location targeting a new destination register.
/// The register in Orig->getOperand(0).getReg() will be substituted by

9
lib/CodeGen/MachineSink.cpp
View File

@ -472,10 +472,6 @@ bool MachineSinking::PostponeSplitCriticalEdge(MachineInstr *MI,
return true;
}
static bool AvoidsSinking(MachineInstr *MI, MachineRegisterInfo *MRI) {
return MI->isInsertSubreg() || MI->isSubregToReg() || MI->isRegSequence();
}
/// collectDebgValues - Scan instructions following MI and collect any
/// matching DBG_VALUEs.
static void collectDebugValues(MachineInstr *MI,
@ -724,9 +720,8 @@ static bool SinkingPreventsImplicitNullCheck(MachineInstr *MI,
/// instruction out of its current block into a successor.
bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore,
AllSuccsCache &AllSuccessors) {
// Don't sink insert_subreg, subreg_to_reg, reg_sequence. These are meant to
// be close to the source to make it easier to coalesce.
if (AvoidsSinking(MI, MRI))
// Don't sink instructions that the target prefers not to sink.
if (!TII->shouldSink(*MI))
return false;
// Check if it's safe to move the instruction.