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cmd/compile: when compiling with -N, avoid entry block

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Lots of constant SSA values we put in the entry block so that
CSE can easily combine them. With -N, however, we don't run CSE, so
putting values in the entry block only serves to extend their lifetime
for no benefit.

Fixes #45897. The number of live SSA values per block goes from >5K to 22.
Memory use goes from ~3GB to ~400MB.

Change-Id: I620b423611790a900e0d4cd270eac5dbdddf2a2b
Reviewed-on: https://go-review.googlesource.com/c/go/+/316369
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Keith Randall 2021-05-03 08:55:57 -07:00
parent 0921211403
commit 5e4f9b077f
1 changed files with 22 additions and 10 deletions
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32
src/cmd/compile/internal/ssagen/ssa.go
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@ -1161,39 +1161,51 @@ func (s *state) newValue4I(op ssa.Op, t *types.Type, aux int64, arg0, arg1, arg2
return s.curBlock.NewValue4I(s.peekPos(), op, t, aux, arg0, arg1, arg2, arg3)
}
func (s *state) entryBlock() *ssa.Block {
b := s.f.Entry
if base.Flag.N > 0 && s.curBlock != nil {
// If optimizations are off, allocate in current block instead. Since with -N
// we're not doing the CSE or tighten passes, putting lots of stuff in the
// entry block leads to O(n^2) entries in the live value map during regalloc.
// See issue 45897.
b = s.curBlock
}
return b
}
// entryNewValue0 adds a new value with no arguments to the entry block.
func (s *state) entryNewValue0(op ssa.Op, t *types.Type) *ssa.Value {
return s.f.Entry.NewValue0(src.NoXPos, op, t)
return s.entryBlock().NewValue0(src.NoXPos, op, t)
}
// entryNewValue0A adds a new value with no arguments and an aux value to the entry block.
func (s *state) entryNewValue0A(op ssa.Op, t *types.Type, aux ssa.Aux) *ssa.Value {
return s.f.Entry.NewValue0A(src.NoXPos, op, t, aux)
return s.entryBlock().NewValue0A(src.NoXPos, op, t, aux)
}
// entryNewValue1 adds a new value with one argument to the entry block.
func (s *state) entryNewValue1(op ssa.Op, t *types.Type, arg *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue1(src.NoXPos, op, t, arg)
return s.entryBlock().NewValue1(src.NoXPos, op, t, arg)
}
// entryNewValue1 adds a new value with one argument and an auxint value to the entry block.
func (s *state) entryNewValue1I(op ssa.Op, t *types.Type, auxint int64, arg *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue1I(src.NoXPos, op, t, auxint, arg)
return s.entryBlock().NewValue1I(src.NoXPos, op, t, auxint, arg)
}
// entryNewValue1A adds a new value with one argument and an aux value to the entry block.
func (s *state) entryNewValue1A(op ssa.Op, t *types.Type, aux ssa.Aux, arg *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue1A(src.NoXPos, op, t, aux, arg)
return s.entryBlock().NewValue1A(src.NoXPos, op, t, aux, arg)
}
// entryNewValue2 adds a new value with two arguments to the entry block.
func (s *state) entryNewValue2(op ssa.Op, t *types.Type, arg0, arg1 *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue2(src.NoXPos, op, t, arg0, arg1)
return s.entryBlock().NewValue2(src.NoXPos, op, t, arg0, arg1)
}
// entryNewValue2A adds a new value with two arguments and an aux value to the entry block.
func (s *state) entryNewValue2A(op ssa.Op, t *types.Type, aux ssa.Aux, arg0, arg1 *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue2A(src.NoXPos, op, t, aux, arg0, arg1)
return s.entryBlock().NewValue2A(src.NoXPos, op, t, aux, arg0, arg1)
}
// const* routines add a new const value to the entry block.
@ -4766,9 +4778,9 @@ func (s *state) openDeferSave(n ir.Node, t *types.Type, val *ssa.Value) *ssa.Val
// declared in the entry block, so that it will be live for the
// defer exit code (which will actually access it only if the
// associated defer call has been activated).
s.defvars[s.f.Entry.ID][memVar] = s.entryNewValue1A(ssa.OpVarDef, types.TypeMem, argTemp, s.defvars[s.f.Entry.ID][memVar])
s.defvars[s.f.Entry.ID][memVar] = s.entryNewValue1A(ssa.OpVarLive, types.TypeMem, argTemp, s.defvars[s.f.Entry.ID][memVar])
addrArgTemp = s.entryNewValue2A(ssa.OpLocalAddr, types.NewPtr(argTemp.Type()), argTemp, s.sp, s.defvars[s.f.Entry.ID][memVar])
s.defvars[s.f.Entry.ID][memVar] = s.f.Entry.NewValue1A(src.NoXPos, ssa.OpVarDef, types.TypeMem, argTemp, s.defvars[s.f.Entry.ID][memVar])
s.defvars[s.f.Entry.ID][memVar] = s.f.Entry.NewValue1A(src.NoXPos, ssa.OpVarLive, types.TypeMem, argTemp, s.defvars[s.f.Entry.ID][memVar])
addrArgTemp = s.f.Entry.NewValue2A(src.NoXPos, ssa.OpLocalAddr, types.NewPtr(argTemp.Type()), argTemp, s.sp, s.defvars[s.f.Entry.ID][memVar])
} else {
// Special case if we're still in the entry block. We can't use
// the above code, since s.defvars[s.f.Entry.ID] isn't defined