JIT: fix arm64 issue around flags and neg with contained operand #113391
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If `neg` has a contained operand (`mul`) it cannot set flags. Fixes dotnet#113320
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Pull Request Overview
This PR introduces a regression test to verify the JIT fix addressing an arm64 issue where a neg instruction with a contained operand (mul) cannot set flags.
- Adds a new test file to capture the faulty behavior
- Verifies JIT behavior on Arm64 in both Debug and Release builds
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Also fixes issue I ran into in #112998. @dotnet/jit-contrib PTAL |
BruceForstall
approved these changes
Mar 11, 2025
EgorBo
reviewed
Mar 11, 2025
| { | ||
| return true; | ||
| } | ||
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| // We do not support setting zero flag for madd/msub. | ||
| if (OperIs(GT_NEG) && (!gtGetOp1()->OperIs(GT_MUL) || !gtGetOp1()->isContained())) |
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I presume just if (OperIs(GT_NEG) && !gtGetOp1()->isContained()) would be enough since NEG can't contain anything. Also, we should've had a separate node type for MUL+ADD/SUB (likely my fault)
EgorBo
approved these changes
Mar 11, 2025
jakobbotsch
reviewed
Mar 11, 2025
| @@ -19978,17 +19978,21 @@ bool GenTree::SupportsSettingZeroFlag() | |||
| } | |||
| #endif | |||
| #elif defined(TARGET_ARM64) | |||
| if (OperIs(GT_AND, GT_AND_NOT, GT_NEG)) | |||
| if (OperIs(GT_AND, GT_AND_NOT)) | |||
| { | |||
| return true; | |||
| } | |||
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| // We do not support setting zero flag for madd/msub. | |||
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Suggested change
| // We do not support setting zero flag for madd/msub. | |
| // We do not support setting zero flag for mneg/madd/msub. |
feel free to skip to avoid CI rerun...
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If
neghas a contained operand (mul) it cannot set flags.Fixes #113320