[llvm] [NFC][GlobalISel] Pass `APInt` by const reference (PR #157827)

[Matt Arsenault via llvm-commits]

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@@ -457,7 +457,8 @@ getFConstantSplat(Register VReg, const MachineRegisterInfo &MRI,
 /// G_BUILD_VECTOR_TRUNC where all of the elements are \p SplatValue or undef.
 LLVM_ABI bool isBuildVectorConstantSplat(const Register Reg,
                                          const MachineRegisterInfo &MRI,
-                                         int64_t SplatValue, bool AllowUndef);
+                                         const APInt &SplatValue,
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arsenm wrote:

This change is unrelated to the title. This should probably have APInt and int64_t overloads 

https://github.com/llvm/llvm-project/pull/157827