[go] cmd/compile: elide sign-extend after zero-extend for wasm

[Gopher Robot (Gerrit)]

Gopher Robot submitted the change

Change information

Commit message:

cmd/compile: elide sign-extend after zero-extend for wasm

Add rules to eliminate sign-extension of values that have already
been zero-extended from fewer bits via an I64And mask:

  (I64Extend32S x:(I64And _ (I64Const [c]))) && c >= 0 && int64(int32(c)) == c => x
  (I64Extend16S x:(I64And _ (I64Const [c]))) && c >= 0 && int64(int16(c)) == c => x
  (I64Extend8S  x:(I64And _ (I64Const [c]))) && c >= 0 && int64(int8(c))  == c => x

When a value has been masked to fit within the non-negative range of
the sign-extension width, the upper bits are already zero and sign-
extending is a no-op. For example, (I64Extend32S (I64And x 0xff))
can be elided because 0xff fits in a signed int32, so bit 31 is
guaranteed to be zero and sign-extending from 32 bits is identity.

Cq-Include-Trybots: luci.golang.try:gotip-wasip1-wasm_wasmtime,gotip-wasip1-wasm_wazero

Change-Id: Ia54d67358756e47ca7635a6a8ca4beadb003820a

Reviewed-on: https://go-review.googlesource.com/c/go/+/756320

Reviewed-by: Keith Randall <k...@google.com>

Reviewed-by: Carlos Amedee <car...@golang.org>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Reviewed-by: Keith Randall <k...@golang.org>

Auto-Submit: Keith Randall <k...@golang.org>

Files:

• M src/cmd/compile/internal/ssa/_gen/Wasm.rules
• M src/cmd/compile/internal/ssa/rewriteWasm.go

Change size: M

Delta: 2 files changed, 67 insertions(+), 0 deletions(-)

Branch: refs/heads/master

Submit Requirements:

• Code-Review: +2 by Keith Randall, +1 by Carlos Amedee, +1 by Keith Randall
• TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

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Gerrit

Gerrit-MessageType: merged

Gerrit-Project: go

Gerrit-Branch: master

Gerrit-Change-Id: Ia54d67358756e47ca7635a6a8ca4beadb003820a

Gerrit-Change-Number: 756320

Gerrit-PatchSet: 3

Gerrit-Owner: George Adams <georgea...@gmail.com>

Gerrit-Reviewer: Carlos Amedee <car...@golang.org>

Gerrit-Reviewer: George Adams <georgea...@gmail.com>

Gerrit-Reviewer: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Gerrit-Reviewer: Gopher Robot <go...@golang.org>

Gerrit-Reviewer: Keith Randall <k...@golang.org>

Gerrit-Reviewer: Keith Randall <k...@google.com>

Gerrit-Reviewer: Martin Möhrmann <moeh...@google.com>