Fix some 16- and 8-bit behavior in x64 backend related to rotates. #3610
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Uncovered by @bjorn3 (thanks!): 8- and 16-bit rotates were not working properly in recent versions of Cranelift with part of the lowering migrated to ISLE. This PR fixes a few issues: - 8- and 16-bit rotate-left needs to mask a constant amount, if any, because we use a 32-bit rotate instruction and so don't get the appropriate shift-amount masking for free from x86 semantics. - `operand_size_from_type` was incorrect: it only handled 32- and 64-bit types and silently returned `OperandSize::Size32` for everything else. Now uses the `OperandSize::from_ty(ty)` helper as the pre-ISLE code did. Our test coverage for narrow value types is not great; this PR adds some runtests for rotl/rotr but more would always be better!
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alexcrichton
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Dec 16, 2021
…e-width for shifts.
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I can confirm this fixes rotate in cg_clif. |
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bjorn3
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Dec 17, 2021
This reverts commit a1037fa. There are two regressions in Cranelift with respect to small integer operations. Both have already been fixed on thebmain branch, but we will have to wait for a new Cranelift release. They have been fixed by bytecodealliance/wasmtime#3610 and bytecodealliance/wasmtime#3617.
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Uncovered by @bjorn3 (thanks!): 8- and 16-bit rotates were not working
properly in recent versions of Cranelift with part of the lowering
migrated to ISLE.
This PR fixes a few issues:
8- and 16-bit rotate-left needs to mask a constant amount, if any,
because we use a 32-bit rotate instruction and so don't get the
appropriate shift-amount masking for free from x86 semantics.
operand_size_from_typewas incorrect: it only handled 32- and 64-bittypes and silently returned
OperandSize::Size32for everything else.Now uses the
OperandSize::from_ty(ty)helper as the pre-ISLE codedid.
Our test coverage for narrow value types is not great; this PR adds some
runtests for rotl/rotr but more would always be better!