cmd/compile/internal/ssa: BCE for induction variables
There are 5293 loop in the main go repository. A survey of the top most common for loops: 18 for __k__ := 0; i < len(sa.Addr); i++ { 19 for __k__ := 0; ; i++ { 19 for __k__ := 0; i < 16; i++ { 25 for __k__ := 0; i < length; i++ { 30 for __k__ := 0; i < 8; i++ { 49 for __k__ := 0; i < len(s); i++ { 67 for __k__ := 0; i < n; i++ { 376 for __k__ := range __slice__ { 685 for __k__, __v__ := range __slice__ { 2074 for __, __v__ := range __slice__ { The algorithm to find induction variables handles all cases with an upper limit. It currently doesn't find related induction variables such as c * ind or c + ind. 842 out of 22954 bound checks are removed for src/make.bash. 1957 out of 42952 bounds checks are removed for src/all.bash. Things to do in follow-up CLs: * Find the associated pointer for `for _, v := range a {}` * Drop the NilChecks on the pointer. * Replace the implicit induction variable by a loop over the pointer Generated garbage can be reduced if we share the sdom between passes. % benchstat old.txt new.txt name old time/op new time/op delta Template 337ms ± 3% 333ms ± 3% ~ (p=0.258 n=9+9) GoTypes 1.11s ± 2% 1.10s ± 2% ~ (p=0.912 n=10+10) Compiler 5.25s ± 1% 5.29s ± 2% ~ (p=0.077 n=9+9) MakeBash 33.5s ± 1% 34.1s ± 2% +1.85% (p=0.011 n=9+9) name old alloc/op new alloc/op delta Template 63.6MB ± 0% 63.9MB ± 0% +0.52% (p=0.000 n=10+9) GoTypes 218MB ± 0% 219MB ± 0% +0.59% (p=0.000 n=10+9) Compiler 978MB ± 0% 985MB ± 0% +0.69% (p=0.000 n=10+10) name old allocs/op new allocs/op delta Template 582k ± 0% 583k ± 0% +0.10% (p=0.000 n=10+10) GoTypes 1.78M ± 0% 1.78M ± 0% +0.12% (p=0.000 n=10+10) Compiler 7.68M ± 0% 7.69M ± 0% +0.05% (p=0.000 n=10+10) name old text-bytes new text-bytes delta HelloSize 581k ± 0% 581k ± 0% -0.08% (p=0.000 n=10+10) CmdGoSize 6.40M ± 0% 6.39M ± 0% -0.08% (p=0.000 n=10+10) name old data-bytes new data-bytes delta HelloSize 3.66k ± 0% 3.66k ± 0% ~ (all samples are equal) CmdGoSize 134k ± 0% 134k ± 0% ~ (all samples are equal) name old bss-bytes new bss-bytes delta HelloSize 126k ± 0% 126k ± 0% ~ (all samples are equal) CmdGoSize 149k ± 0% 149k ± 0% ~ (all samples are equal) name old exe-bytes new exe-bytes delta HelloSize 947k ± 0% 946k ± 0% -0.01% (p=0.000 n=10+10) CmdGoSize 9.92M ± 0% 9.91M ± 0% -0.06% (p=0.000 n=10+10) Change-Id: Ie74bdff46fd602db41bb457333d3a762a0c3dc4d Reviewed-on: https://go-review.googlesource.com/20517Reviewed-by:David Chase <drchase@google.com> Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
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test/loopbce.go
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