[libc-commits] [clang] [libc] [llvm] [NVPTX] Implement variadic functions using IR lowering (PR #96015)

[Joseph Huber via libc-commits]

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@@ -938,6 +938,37 @@ 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 doesn't apply minimum alignment to types present in structs. Types
+    // with alignment less than four should be promoted by the compiler and will
+    // get the proper minimum alignment in those cases.
+    const unsigned MinAlign = 1;
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jhuber6 wrote:

So, the standard varargs handling will automatically promote things like shorts to ints and floats to doubles. What the comment means is that `clang` already handled the size / alignment in those cases, so we need to use a minimum alignment of 1 so we respect the alignment for things that clang didn't modify.

https://github.com/llvm/llvm-project/pull/96015