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| author | Jorropo <jorropo.pgm@gmail.com> | 2023-07-25 16:19:10 +0200 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2023-07-31 18:33:29 +0000 |
| commit | bac4e2f241ca8df3d5be6ddf83214b9a681f4086 (patch) | |
| tree | 6fcd6b62c19354d7e6ba9496a764976982db0c16 /src/cmd/compile/internal/ssa/loopbce.go | |
| parent | 8613ef81e676bda77f6413a587e68c3dcc5b03ae (diff) | |
| download | go-bac4e2f241ca8df3d5be6ddf83214b9a681f4086.tar.xz | |
cmd/compile: try to rewrite loops to count down
Fixes #61629
This reduce the pressure on regalloc because then the loop only keep alive
one value (the iterator) instead of the iterator and the upper bound since
the comparison now acts against an immediate, often zero which can be skipped.
This optimize things like:
for i := 0; i < n; i++ {
Or a range over a slice where the index is not used:
for _, v := range someSlice {
Or the new range over int from #61405:
for range n {
It is hit in 975 unique places while doing ./make.bash.
Change-Id: I5facff8b267a0b60ea3c1b9a58c4d74cdb38f03f
Reviewed-on: https://go-review.googlesource.com/c/go/+/512935
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Diffstat (limited to 'src/cmd/compile/internal/ssa/loopbce.go')
| -rw-r--r-- | src/cmd/compile/internal/ssa/loopbce.go | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/cmd/compile/internal/ssa/loopbce.go b/src/cmd/compile/internal/ssa/loopbce.go index b7dfaa33e3..3dbd7350ae 100644 --- a/src/cmd/compile/internal/ssa/loopbce.go +++ b/src/cmd/compile/internal/ssa/loopbce.go @@ -13,12 +13,14 @@ import ( type indVarFlags uint8 const ( - indVarMinExc indVarFlags = 1 << iota // minimum value is exclusive (default: inclusive) - indVarMaxInc // maximum value is inclusive (default: exclusive) + indVarMinExc indVarFlags = 1 << iota // minimum value is exclusive (default: inclusive) + indVarMaxInc // maximum value is inclusive (default: exclusive) + indVarCountDown // if set the iteration starts at max and count towards min (default: min towards max) ) type indVar struct { ind *Value // induction variable + nxt *Value // the incremented variable min *Value // minimum value, inclusive/exclusive depends on flags max *Value // maximum value, inclusive/exclusive depends on flags entry *Block // entry block in the loop. @@ -277,6 +279,7 @@ func findIndVar(f *Func) []indVar { if !inclusive { flags |= indVarMinExc } + flags |= indVarCountDown step = -step } if f.pass.debug >= 1 { @@ -285,6 +288,7 @@ func findIndVar(f *Func) []indVar { iv = append(iv, indVar{ ind: ind, + nxt: nxt, min: min, max: max, entry: b.Succs[0].b, |