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cmd/compile: PPC64 folds (MOVWZreg (RLWINM x)) incorrectly in some cases #67844

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pmur opened this issue Jun 5, 2024 · 4 comments
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cmd/compile: PPC64 folds (MOVWZreg (RLWINM x)) incorrectly in some cases #67844

pmur opened this issue Jun 5, 2024 · 4 comments
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@pmur
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compiler/runtime Issues related to the Go compiler and/or runtime. FixPending Issues that have a fix which has not yet been reviewed or submitted. NeedsFix The path to resolution is known, but the work has not been done. release-blocker
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Go1.23

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@pmur
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pmur commented Jun 5, 2024

Go version

master

Output of go env in your module/workspace:

GOARCH=ppc64le

What did you do?

Adding the following codegen test to bitRotateAndMask:

        // ppc64x: "MOVWZ", "RLWNM\t[$]1, R[0-9]*, [$]28, [$]3, R"
        io64[3] = uint64(bits.RotateLeft32(io32[0],1) & 0xF000000F)

What did you see happen?

The MOVWZ is missing.

What did you expect to see?

The MOVWZ opcode should be present for certain usages of RLWINM to ensure the upper 32 bits are cleared when the value is expected to be zero-extended.
@pmur pmur added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jun 5, 2024
@pmur pmur self-assigned this Jun 5, 2024
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Change https://go.dev/cl/590896 mentions this issue: cmd/compile/ssa: fix (MOVWZreg (RLWINM)) folding on PPC64

@randall77 randall77 added this to the Go1.23 milestone Jun 7, 2024
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Do we need this fix backported?

@pmur
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pmur commented Jun 7, 2024

No, I added this rule in 1.23.

@dmitshur dmitshur added NeedsFix The path to resolution is known, but the work has not been done. FixPending Issues that have a fix which has not yet been reviewed or submitted. labels Jun 7, 2024
@dmitshur dmitshur moved this to In Progress in Release Blockers Jun 7, 2024
@github-project-automation github-project-automation bot moved this from In Progress to Done in Release Blockers Jun 7, 2024
@gabyhelp gabyhelp mentioned this issue Jun 8, 2024
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@pmur pmur

Labels
compiler/runtime Issues related to the Go compiler and/or runtime. FixPending Issues that have a fix which has not yet been reviewed or submitted. NeedsFix The path to resolution is known, but the work has not been done. release-blocker
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Release Blockers
Status: Done
Milestone
Go1.23
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@dmitshur @randall77 @gopherbot @pmur