[llvm] AMDGPU/GlobalISel: Handle G_BITCAST for 16 bit extendedLLTs (PR #208750)

[Matt Arsenault via llvm-commits]

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@@ -2704,6 +2711,15 @@ bool AMDGPULegalizerInfo::legalizeAddrSpaceCast(
   return true;
 }
 
+bool AMDGPULegalizerInfo::legalizeBitcast(MachineInstr &MI,
+                                          MachineRegisterInfo &MRI,
+                                          MachineIRBuilder &B) const {
+  B.buildTrunc(MI.getOperand(0).getReg(),
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arsenm wrote:

There's nothing custom about this, this is just widenScalar on the source 

https://github.com/llvm/llvm-project/pull/208750