[pull] master from golang:master#100
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…bnormal When fadd64/fsub64 cancel two near-equal, opposite-sign normal operands into a subnormal result, fpack64 is handed a mantissa far below 1<<mantbits64 while exp is still a normal-range exponent. fpack64 saved mant0/exp0/trunc0 before its normalization loop, so the denormal branch restored an un-normalized mantissa and right-shifted it to align to the subnormal exponent (the wrong direction here), returning the un-normalized cancellation mantissa at the wrong scale instead of the correctly rounded subnormal. Save mant0/exp0/trunc0 after the normalization loop so the denormal path restores a normalized mantissa and aligns correctly. This is a no-op for callers that already pass a normalized mantissa (fmul64, fdiv64, conversions). fpack32 is updated identically for parity, though its denormal branch is not reachable with an un-normalized mantissa through any current caller. This only manifests on softfloat targets (e.g. GOMIPS=softfloat), which is why it has gone unnoticed on hardware-float platforms. A randomized differential check against hardware found the previous code wrong on >50% of normal pairs that cancel into a subnormal; with this change those cases match hardware. Fixes #79964 Change-Id: I29f7ec79905ddb98af4f997a69b0a2f0574c3c9d GitHub-Last-Rev: 42a73cd GitHub-Pull-Request: #79965 Reviewed-on: https://go-review.googlesource.com/c/go/+/789861 Reviewed-by: Sayer Turner <sayerturner65@gmail.com> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Keith Randall <khr@golang.org> Auto-Submit: Keith Randall <khr@golang.org> LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TestCtrlBreak relied on a fixed sleep to wait for a testing child program to be ready to receive the signal. This may cause flaky timeouts on slow machines. Instead, wait for the child to print a "ready" message like other signal tests, particularly runtime.TestLibraryCtrlHandler. Also fix a typo in the child program's file name to ensure it's easy to associate with the test. Fixes #80036 Change-Id: Ib3d8e6194538df95e76548771b401cf9b9de5674 Reviewed-on: https://go-review.googlesource.com/c/go/+/792020 LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Alex Brainman <alex.brainman@gmail.com> Reviewed-by: Hongxiang Jiang <hxjiang@golang.org> Auto-Submit: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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