[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);
+    if (A < MinAlign)
+      A = Align(MinAlign);
+    return {A, false};
+  }
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JonChesterfield wrote:

Are you really looking for `if (A < 1) A = 1;` here? Align has max/min functions which would be clearer

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