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cmd/compile: cache CFG-dependent computations

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We compute a lot of stuff based off the CFG: postorder traversal,
dominators, dominator tree, loop nest.  Multiple phases use this
information and we end up recomputing some of it.  Add a cache
for this information so if the CFG hasn't changed, we can reuse
the previous computation.

Change-Id: I9b5b58af06830bd120afbee9cfab395a0a2f74b2
Reviewed-on: https://go-review.googlesource.com/29356
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Keith Randall 2016-09-16 13:50:18 -07:00
parent 2679282da4
commit 75ce89c20d
18 changed files with 83 additions and 59 deletions
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7
src/cmd/compile/internal/ssa/compile.go
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@ -250,7 +250,6 @@ var passes = [...]pass{
{name: "opt", fn: opt, required: true}, // TODO: split required rules and optimizing rules
{name: "zero arg cse", fn: zcse, required: true}, // required to merge OpSB values
{name: "opt deadcode", fn: deadcode, required: true}, // remove any blocks orphaned during opt
{name: "generic domtree", fn: domTree},
{name: "generic cse", fn: cse},
{name: "phiopt", fn: phiopt},
{name: "nilcheckelim", fn: nilcheckelim},
@ -308,12 +307,6 @@ var passOrder = [...]constraint{
{"opt", "nilcheckelim"},
// tighten should happen before lowering to avoid splitting naturally paired instructions such as CMP/SET
{"tighten", "lower"},
// cse, phiopt, nilcheckelim, prove and loopbce share idom.
{"generic domtree", "generic cse"},
{"generic domtree", "phiopt"},
{"generic domtree", "nilcheckelim"},
{"generic domtree", "prove"},
{"generic domtree", "loopbce"},
// tighten will be most effective when as many values have been removed as possible
{"generic deadcode", "tighten"},
{"generic cse", "tighten"},