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author | Dimitry Andric <dim@FreeBSD.org> | 2016-01-13 19:58:01 +0000 |
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committer | Dimitry Andric <dim@FreeBSD.org> | 2016-01-13 19:58:01 +0000 |
commit | 050e163ae8b4bb6eb252b59e2f8f36e68ae9239d (patch) | |
tree | 7376a0c71aad05d327e5b1dcbceb3311a10f9f29 /lib/CodeGen/MachineInstr.cpp | |
parent | 8a6c1c25bce0267ee4072bd7b786b921e8a66a35 (diff) | |
download | src-test2-050e163ae8b4bb6eb252b59e2f8f36e68ae9239d.tar.gz src-test2-050e163ae8b4bb6eb252b59e2f8f36e68ae9239d.zip |
Notes
Diffstat (limited to 'lib/CodeGen/MachineInstr.cpp')
-rw-r--r-- | lib/CodeGen/MachineInstr.cpp | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp index 6b8eeccd173d..6dca74d60026 100644 --- a/lib/CodeGen/MachineInstr.cpp +++ b/lib/CodeGen/MachineInstr.cpp @@ -866,14 +866,44 @@ void MachineInstr::addMemOperand(MachineFunction &MF, setMemRefs(NewMemRefs, NewMemRefs + NewNum); } +/// Check to see if the MMOs pointed to by the two MemRefs arrays are +/// identical. +static bool hasIdenticalMMOs(const MachineInstr &MI1, const MachineInstr &MI2) { + auto I1 = MI1.memoperands_begin(), E1 = MI1.memoperands_end(); + auto I2 = MI2.memoperands_begin(), E2 = MI2.memoperands_end(); + if ((E1 - I1) != (E2 - I2)) + return false; + for (; I1 != E1; ++I1, ++I2) { + if (**I1 != **I2) + return false; + } + return true; +} + std::pair<MachineInstr::mmo_iterator, unsigned> MachineInstr::mergeMemRefsWith(const MachineInstr& Other) { - // TODO: If we end up with too many memory operands, return the empty - // conservative set rather than failing asserts. + + // If either of the incoming memrefs are empty, we must be conservative and + // treat this as if we've exhausted our space for memrefs and dropped them. + if (memoperands_empty() || Other.memoperands_empty()) + return std::make_pair(nullptr, 0); + + // If both instructions have identical memrefs, we don't need to merge them. + // Since many instructions have a single memref, and we tend to merge things + // like pairs of loads from the same location, this catches a large number of + // cases in practice. + if (hasIdenticalMMOs(*this, Other)) + return std::make_pair(MemRefs, NumMemRefs); + // TODO: consider uniquing elements within the operand lists to reduce // space usage and fall back to conservative information less often. - size_t CombinedNumMemRefs = (memoperands_end() - memoperands_begin()) - + (Other.memoperands_end() - Other.memoperands_begin()); + size_t CombinedNumMemRefs = NumMemRefs + Other.NumMemRefs; + + // If we don't have enough room to store this many memrefs, be conservative + // and drop them. Otherwise, we'd fail asserts when trying to add them to + // the new instruction. + if (CombinedNumMemRefs != uint8_t(CombinedNumMemRefs)) + return std::make_pair(nullptr, 0); MachineFunction *MF = getParent()->getParent(); mmo_iterator MemBegin = MF->allocateMemRefsArray(CombinedNumMemRefs); |