[llvm] [TLI] Fix replace-with-veclib crash with invalid arguments (PR #77112)

[Paschalis Mpeis via llvm-commits]

================
@@ -0,0 +1,89 @@
+//===--- ReplaceWithVecLibTest.cpp - replace-with-veclib unit tests -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/ReplaceWithVeclib.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+static std::unique_ptr<Module> parseIR(LLVMContext &C, const char *IR) {
+  SMDiagnostic Err;
+  std::unique_ptr<Module> Mod = parseAssemblyString(IR, Err, C);
+  if (!Mod)
+    Err.print("ReplaceWithVecLibTest", errs());
+  return Mod;
+}
+
+/// Runs ReplaceWithVecLib with different TLIIs that have custom VecDescs. This
+/// allows checking that the pass won't crash when the function to replace (from
+/// the input IR) does not match the replacement function (derived from the
+/// VecDesc mapping).
+class ReplaceWithVecLibTest : public ::testing::Test {
+protected:
+  LLVMContext Ctx;
+
+  /// Creates TLII using the given \p VD, and then runs the ReplaceWithVeclib
+  /// pass. The pass should not crash even when the replacement function
+  /// (derived from the \p VD mapping) does not match the function to be
+  /// replaced (from the input \p IR).
+  bool run(const VecDesc &VD, const char *IR) {
+    // Create TLII and register it with FAM so it's preserved when
+    // ReplaceWithVeclib pass runs.
+    TargetLibraryInfoImpl TLII = TargetLibraryInfoImpl(Triple());
+    TLII.addVectorizableFunctions({VD});
+    FunctionAnalysisManager FAM;
+    FAM.registerPass([&TLII]() { return TargetLibraryAnalysis(TLII); });
+
+    // Register and run the pass on the 'foo' function from the input IR.
+    FunctionPassManager FPM;
+    FPM.addPass(ReplaceWithVeclib());
+    std::unique_ptr<Module> M = parseIR(Ctx, IR);
+    PassBuilder PB;
+    PB.registerFunctionAnalyses(FAM);
+    FPM.run(*M->getFunction("foo"), FAM);
+
+    return true;
+  }
+};
+
+} // end anonymous namespace
+
+static const char *IR = R"IR(
+define <vscale x 4 x float> @foo(<vscale x 4 x float> %in){
+  %call = call <vscale x 4 x float> @llvm.powi.f32.i32(<vscale x 4 x float> %in, i32 3)
+  ret <vscale x 4 x float> %call
+}
+
+declare <vscale x 4 x float> @llvm.powi.f32.i32(<vscale x 4 x float>, i32) #0
+)IR";
+
+// The VFABI prefix in TLI describes signature which is matching the powi
+// intrinsic declaration.
+TEST_F(ReplaceWithVecLibTest, TestValidMapping) {
+  VecDesc CorrectVD = {"llvm.powi.f32.i32", "_ZGVsMxvu_powi",
+                       ElementCount::getScalable(4), /*Masked*/ true,
+                       "_ZGVsMxvu"};
+  EXPECT_TRUE(run(CorrectVD, IR));
+}
+
+// The VFABI prefix in TLI describes signature which is not matching the powi
+// intrinsic declaration.
+TEST_F(ReplaceWithVecLibTest, TestInvalidMapping) {
+  VecDesc IncorrectVD = {"llvm.powi.f32.i32", "_ZGVsMxvv_powi",
+                         ElementCount::getScalable(4), /*Masked*/ true,
+                         "_ZGVsMxvv"};
+  EXPECT_TRUE(run(IncorrectVD, IR));
----------------
paschalis-mpeis wrote:

Discussed offline and @mgabka some inspiration how to test this by capturing std err.

https://github.com/llvm/llvm-project/pull/77112