[llvm] [X86] Add custom operation actions for f16: FABS, FNEG, and FCOPYSIGN (PR #128877)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Prashanth (StarOne01)

<details>
<summary>Changes</summary>

This pull request adds custom handling for several floating-point operations for the `f16` type with respect to (https://github.com/llvm/llvm-project/issues/126892)..

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Full diff: https://github.com/llvm/llvm-project/pull/128877.diff


1 Files Affected:

- (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+3) 


``````````diff
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index a4357197e2843..5a80754e7a3bb 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -701,6 +701,9 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     setOperationAction(ISD::FSUB, MVT::f16, Promote);
     setOperationAction(ISD::FMUL, MVT::f16, Promote);
     setOperationAction(ISD::FDIV, MVT::f16, Promote);
+    setOperationAction(ISD::FABS, MVT::f16, Custom);
+    setOperationAction(ISD::FNEG, MVT::f16, Custom);
+    setOperationAction(ISD::FCOPYSIGN, MVT::f16, Custom);
     setOperationAction(ISD::FP_ROUND, MVT::f16, Custom);
     setOperationAction(ISD::FP_EXTEND, MVT::f32, Custom);
     setOperationAction(ISD::FP_EXTEND, MVT::f64, Custom);

``````````

</details>


https://github.com/llvm/llvm-project/pull/128877