[clang] [libc] [llvm] [libc] Implement (v|f)printf on the GPU (PR #96369)

[Jon Chesterfield via cfe-commits]

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@@ -942,6 +942,36 @@ struct Amdgpu final : public VariadicABIInfo {
   }
 };
 
+struct NVPTX final : public VariadicABIInfo {
+
+  bool enableForTarget() override { return true; }
+
+  bool vaListPassedInSSARegister() override { return true; }
+
+  Type *vaListType(LLVMContext &Ctx) override {
+    return PointerType::getUnqual(Ctx);
+  }
+
+  Type *vaListParameterType(Module &M) override {
+    return PointerType::getUnqual(M.getContext());
+  }
+
+  Value *initializeVaList(Module &M, LLVMContext &Ctx, IRBuilder<> &Builder,
+                          AllocaInst *, Value *Buffer) override {
+    return Builder.CreateAddrSpaceCast(Buffer, vaListParameterType(M));
+  }
+
+  VAArgSlotInfo slotInfo(const DataLayout &DL, Type *Parameter) override {
+    // NVPTX expects natural alignment in all cases. The variadic call ABI will
+    // handle promoting types to their appropriate size and alignment.
+    const unsigned MinAlign = 1;
+    Align A = DL.getABITypeAlign(Parameter);
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JonChesterfield wrote:

can getABITypeAlign return 0?

Does nvptx actually expect natural alignment? That would be inconsistent with the slot size of four which strongly suggests everything is passed with at least four byte alignment

https://github.com/llvm/llvm-project/pull/96369