[Mlir-commits] [mlir] [mlir][llvm] Do not inline variadic functions (PR #77241)

[Tobias Gysi]

https://github.com/gysit updated https://github.com/llvm/llvm-project/pull/77241

>From 493cc38186cb3ce9416efe00b6583c73266ef29f Mon Sep 17 00:00:00 2001
From: Tobias Gysi <tobias.gysi at nextsilicon.com>
Date: Sun, 7 Jan 2024 14:11:14 +0000
Subject: [PATCH] [mlir][llvm] Do not inline variadic functions

This revision updates the llvm dialect inliner to explicitly disallow
the inlining of variadic functions. Already previously the inlining
failed if the number of function arguments did not match the number of
call arguments. After the change, inlining checks the function is not
variadic and it does not contain a va_start intrinsic.
---
 mlir/lib/Dialect/LLVMIR/IR/LLVMInlining.cpp |  7 +++++-
 mlir/test/Dialect/LLVMIR/inlining.mlir      | 25 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/mlir/lib/Dialect/LLVMIR/IR/LLVMInlining.cpp b/mlir/lib/Dialect/LLVMIR/IR/LLVMInlining.cpp
index 65c1daee6711ad..4a6154ea6d3004 100644
--- a/mlir/lib/Dialect/LLVMIR/IR/LLVMInlining.cpp
+++ b/mlir/lib/Dialect/LLVMIR/IR/LLVMInlining.cpp
@@ -663,6 +663,10 @@ struct LLVMInlinerInterface : public DialectInlinerInterface {
                  << "Cannot inline: callable is not an LLVM::LLVMFuncOp\n");
       return false;
     }
+    if (funcOp.isVarArg()) {
+      LLVM_DEBUG(llvm::dbgs() << "Cannot inline: callable is variadic\n");
+      return false;
+    }
     // TODO: Generate aliasing metadata from noalias argument/result attributes.
     if (auto attrs = funcOp.getArgAttrs()) {
       for (DictionaryAttr attrDict : attrs->getAsRange<DictionaryAttr>()) {
@@ -704,7 +708,8 @@ struct LLVMInlinerInterface : public DialectInlinerInterface {
   }
 
   bool isLegalToInline(Operation *op, Region *, bool, IRMapping &) const final {
-    return true;
+    // The inliner cannot handle variadic function arguments.
+    return !isa<LLVM::VaStartOp>(op);
   }
 
   /// Handle the given inlined return by replacing it with a branch. This
diff --git a/mlir/test/Dialect/LLVMIR/inlining.mlir b/mlir/test/Dialect/LLVMIR/inlining.mlir
index 63e7a46f1bdb06..3af8753bc318ab 100644
--- a/mlir/test/Dialect/LLVMIR/inlining.mlir
+++ b/mlir/test/Dialect/LLVMIR/inlining.mlir
@@ -644,3 +644,28 @@ llvm.func @caller(%ptr : !llvm.ptr) -> i32 {
   llvm.store %c5, %ptr { access_groups = [#caller] } : i32, !llvm.ptr
   llvm.return %0 : i32
 }
+
+// -----
+
+llvm.func @vararg_func(...) {
+  llvm.return
+}
+
+llvm.func @vararg_intrinrics() {
+  %0 = llvm.mlir.constant(1 : i32) : i32
+  %list = llvm.alloca %0 x !llvm.struct<"struct.va_list_opaque", (ptr)> : (i32) -> !llvm.ptr
+  // The vararg intinriscs should normally be part of a variadic function.
+  // However, this test uses a non-variadic function to ensure the presence of
+  // the intrinsic alone suffices to prevent inlining.
+  llvm.intr.vastart %list : !llvm.ptr
+  llvm.return
+}
+
+// CHECK-LABEL: func @caller
+llvm.func @caller() {
+  // CHECK-NEXT: llvm.call @vararg_func()
+  llvm.call @vararg_func() vararg(!llvm.func<void (...)>) : () -> ()
+  // CHECK-NEXT: llvm.call @vararg_intrinrics()
+  llvm.call @vararg_intrinrics() : () -> ()
+  llvm.return
+}