[CodeGen] Allocate RegAllocHints map lazily #102186
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This hint map is not required whenever a new register is added, in fact, at -O0, it is not used at all. Growing this map is quite expensive, as SmallVectors are not trivially copyable. Grow this map only when hints are actually added to avoid multiple grows and grows when no hints are added at all.
arsenm
approved these changes
Aug 6, 2024
topperc
reviewed
Aug 7, 2024
| @@ -801,6 +801,7 @@ class MachineRegisterInfo { | |||
| /// of an earlier hint it will be overwritten. | |||
| void setRegAllocationHint(Register VReg, unsigned Type, Register PrefReg) { | |||
| assert(VReg.isVirtual()); | |||
| RegAllocHints.grow(Register::index2VirtReg(getNumVirtRegs())); | |||
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Should this be getNumVirtRegs() - 1? grow expects an index. getNumVRegs() is one past the largest index. Or maybe we could use resize?
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Good catch, opened #102273
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/66/builds/2559 Here is the relevant piece of the build log for the reference: |
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This hint map is not required whenever a new register is added, in fact, at -O0, it is not used at all. Growing this map is quite expensive, as SmallVectors are not trivially copyable.
Grow this map only when hints are actually added to avoid multiple grows and grows when no hints are added at all.
c-t-t