[llvm] [AMDGPU][True16] Legalize S16 for stores & loads in GlobalISel when True16 is enabled (PR #176963)

[Matt Arsenault via llvm-commits]

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@@ -1573,6 +1573,15 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST_,
                                       {V4S32, ConstantPtr, V4S32, GlobalAlign32},
                                       {S64, ConstantPtr, S64, GlobalAlign32},
                                       {V2S32, ConstantPtr, V2S32, GlobalAlign32}});
+
+    if (ST.useRealTrue16Insts())
+      Actions.legalForTypesWithMemDesc({{S16, GlobalPtr, S8, GlobalAlign8},
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arsenm wrote:

I meant this will require adding a new form of predicated legalForTypesWithMemDesc, you can't just use legalIf as it is 

https://github.com/llvm/llvm-project/pull/176963