TheRock/compiler/amd-llvm/llvm/unittests/Analysis/IVDescriptorsTest.cpp

//===- IVDescriptorsTest.cpp - IVDescriptors 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/Analysis/IVDescriptors.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/AsmParser/Parser.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"

using namespace llvm;

/// Build the loop info and scalar evolution for the function and run the Test.
static void runWithLoopInfoAndSE(
    Module &M, StringRef FuncName,
    function_ref<void(Function &F, LoopInfo &LI, ScalarEvolution &SE)> Test) {
  auto *F = M.getFunction(FuncName);
  ASSERT_NE(F, nullptr) << "Could not find " << FuncName;

  TargetLibraryInfoImpl TLII(M.getTargetTriple());
  TargetLibraryInfo TLI(TLII);
  AssumptionCache AC(*F);
  DominatorTree DT(*F);
  LoopInfo LI(DT);
  ScalarEvolution SE(*F, TLI, AC, DT, LI);

  Test(*F, LI, SE);
}

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("IVDescriptorsTests", errs());
  return Mod;
}

// This tests that IVDescriptors can obtain the induction binary operator for
// integer induction variables. And getExactFPMathInst() correctly return the
// expected behavior, i.e. no FMF algebra.
TEST(IVDescriptorsTest, LoopWithSingleLatch) {
  // Parse the module.
  LLVMContext Context;

  std::unique_ptr<Module> M = parseIR(
    Context,
    R"(define void @foo(ptr %A, i32 %ub) {
entry:
  br label %for.body
for.body:
  %i = phi i32 [ 0, %entry ], [ %inc, %for.body ]
  %idxprom = sext i32 %i to i64
  %arrayidx = getelementptr inbounds i32, ptr %A, i64 %idxprom
  store i32 %i, ptr %arrayidx, align 4
  %inc = add nsw i32 %i, 1
  %cmp = icmp slt i32 %inc, %ub
  br i1 %cmp, label %for.body, label %for.exit
for.exit:
  br label %for.end
for.end:
  ret void
})"
    );

  runWithLoopInfoAndSE(
      *M, "foo", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
        Function::iterator FI = F.begin();
        // First basic block is entry - skip it.
        BasicBlock *Header = &*(++FI);
        assert(Header->getName() == "for.body");
        Loop *L = LI.getLoopFor(Header);
        EXPECT_NE(L, nullptr);
        PHINode *Inst_i = dyn_cast<PHINode>(&Header->front());
        assert(Inst_i->getName() == "i");
        InductionDescriptor IndDesc;
        bool IsInductionPHI =
            InductionDescriptor::isInductionPHI(Inst_i, L, &SE, IndDesc);
        EXPECT_TRUE(IsInductionPHI);
        Instruction *Inst_inc = nullptr;
        BasicBlock::iterator BBI = Header->begin();
        do {
          if ((&*BBI)->getName() == "inc")
            Inst_inc = &*BBI;
          ++BBI;
        } while (!Inst_inc);
        assert(Inst_inc->getName() == "inc");
        EXPECT_EQ(IndDesc.getInductionBinOp(), Inst_inc);
        EXPECT_EQ(IndDesc.getExactFPMathInst(), nullptr);
      });
}

// Depending on how SCEV deals with ptrtoint cast, the step of a phi could be
// a pointer, and InductionDescriptor used to fail with an assertion.
// So just check that it doesn't assert.
TEST(IVDescriptorsTest, LoopWithPtrToInt) {
  // Parse the module.
  LLVMContext Context;

  std::unique_ptr<Module> M = parseIR(Context, R"(
      target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
      target triple = "thumbv6m-arm-none-eabi"

      declare void @widget()
      declare void @wobble(i32)

      define void @barney(ptr %arg, ptr %arg18, i32 %arg19) {
      bb:
        %tmp = ptrtoint ptr %arg to i32
        %tmp20 = ptrtoint ptr %arg18 to i32
        %tmp21 = or i32 %tmp20, %tmp
        %tmp22 = and i32 %tmp21, 3
        %tmp23 = icmp eq i32 %tmp22, 0
        br i1 %tmp23, label %bb24, label %bb25

      bb24:
        tail call void @widget()
        br label %bb34

      bb25:
        %tmp26 = sub i32 %tmp, %tmp20
        %tmp27 = icmp ult i32 %tmp26, %arg19
        br i1 %tmp27, label %bb28, label %bb34

      bb28:
        br label %bb29

      bb29:
        %tmp30 = phi i32 [ %tmp31, %bb29 ], [ %arg19, %bb28 ]
        tail call void @wobble(i32 %tmp26)
        %tmp31 = sub i32 %tmp30, %tmp26
        %tmp32 = icmp ugt i32 %tmp31, %tmp26
        br i1 %tmp32, label %bb29, label %bb33

      bb33:
        br label %bb34

      bb34:
        ret void
      })");

  runWithLoopInfoAndSE(
      *M, "barney", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
        Function::iterator FI = F.begin();
        // First basic block is entry - skip it.
        BasicBlock *Header = &*(++(++(++(++FI))));
        assert(Header->getName() == "bb29");
        Loop *L = LI.getLoopFor(Header);
        EXPECT_NE(L, nullptr);
        PHINode *Inst_i = dyn_cast<PHINode>(&Header->front());
        assert(Inst_i->getName() == "tmp30");
        InductionDescriptor IndDesc;
        bool IsInductionPHI =
            InductionDescriptor::isInductionPHI(Inst_i, L, &SE, IndDesc);
        EXPECT_TRUE(IsInductionPHI);
      });
}

// This tests that correct identity value is returned for a RecurrenceDescriptor
// that describes FMin reduction idiom.
TEST(IVDescriptorsTest, FMinRednIdentity) {
  // Parse the module.
  LLVMContext Context;

  std::unique_ptr<Module> M = parseIR(Context,
                                      R"(define float @foo(ptr %A, i64 %ub) {
entry:
  br label %for.body

for.body:
  %i = phi i64 [ 0, %entry ], [ %i.next, %for.body ]
  %fmin = phi float [ 1.000000e+00, %entry ], [ %fmin.next, %for.body ]
  %arrayidx = getelementptr inbounds float, ptr %A, i64 %i
  %ld = load float, ptr %arrayidx
  %fmin.cmp = fcmp nnan nsz olt float %fmin, %ld
  %fmin.next = select nnan nsz i1 %fmin.cmp, float %fmin, float %ld
  %i.next = add nsw i64 %i, 1
  %cmp = icmp slt i64 %i.next, %ub
  br i1 %cmp, label %for.body, label %for.end

for.end:
  %fmin.lcssa = phi float [ %fmin.next, %for.body ]
  ret float %fmin.lcssa
})");

  runWithLoopInfoAndSE(
      *M, "foo", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
        Function::iterator FI = F.begin();
        // First basic block is entry - skip it.
        BasicBlock *Header = &*(++FI);
        assert(Header->getName() == "for.body");
        Loop *L = LI.getLoopFor(Header);
        EXPECT_NE(L, nullptr);
        BasicBlock::iterator BBI = Header->begin();
        assert((&*BBI)->getName() == "i");
        ++BBI;
        PHINode *Phi = dyn_cast<PHINode>(&*BBI);
        assert(Phi->getName() == "fmin");
        RecurrenceDescriptor Rdx;
        bool IsRdxPhi = RecurrenceDescriptor::isReductionPHI(Phi, L, Rdx);
        EXPECT_TRUE(IsRdxPhi);
        RecurKind Kind = Rdx.getRecurrenceKind();
        EXPECT_EQ(Kind, RecurKind::FMin);
      });
}

// This tests that correct identity value is returned for a RecurrenceDescriptor
// that describes FMax reduction idiom.
TEST(IVDescriptorsTest, FMaxRednIdentity) {
  // Parse the module.
  LLVMContext Context;

  std::unique_ptr<Module> M = parseIR(Context,
                                      R"(define float @foo(ptr %A, i64 %ub) {
entry:
  br label %for.body

for.body:
  %i = phi i64 [ 0, %entry ], [ %i.next, %for.body ]
  %fmax = phi float [ 1.000000e+00, %entry ], [ %fmax.next, %for.body ]
  %arrayidx = getelementptr inbounds float, ptr %A, i64 %i
  %ld = load float, ptr %arrayidx
  %fmax.cmp = fcmp nnan nsz ogt float %fmax, %ld
  %fmax.next = select nnan nsz i1 %fmax.cmp, float %fmax, float %ld
  %i.next = add nsw i64 %i, 1
  %cmp = icmp slt i64 %i.next, %ub
  br i1 %cmp, label %for.body, label %for.end

for.end:
  %fmax.lcssa = phi float [ %fmax.next, %for.body ]
  ret float %fmax.lcssa
})");

  runWithLoopInfoAndSE(
      *M, "foo", [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
        Function::iterator FI = F.begin();
        // First basic block is entry - skip it.
        BasicBlock *Header = &*(++FI);
        assert(Header->getName() == "for.body");
        Loop *L = LI.getLoopFor(Header);
        EXPECT_NE(L, nullptr);
        BasicBlock::iterator BBI = Header->begin();
        assert((&*BBI)->getName() == "i");
        ++BBI;
        PHINode *Phi = dyn_cast<PHINode>(&*BBI);
        assert(Phi->getName() == "fmax");
        RecurrenceDescriptor Rdx;
        bool IsRdxPhi = RecurrenceDescriptor::isReductionPHI(Phi, L, Rdx);
        EXPECT_TRUE(IsRdxPhi);
        RecurKind Kind = Rdx.getRecurrenceKind();
        EXPECT_EQ(Kind, RecurKind::FMax);
      });
}

TEST(IVDescriptorsTest, UnsupportedFindLastPhi) {
  // Parse the module.
  LLVMContext Context;

  // This is a constructed example for the test, but it's based on a loop like:
  //  int result = default_val;
  //  for (int i = 0; i < N; ++i) {
  //    if (cond_0) {
  //      if (cond_1)
  //        result = v1;
  //    } else {
  //      if (cond_1)
  //        result = v2;
  //    }
  //  }
  //  return result;
  std::unique_ptr<Module> M = parseIR(Context, R"(
    define i64 @unsupported_find_last_phi(
      i64 %v1, i64 %v2, i64 %default_val, i64 %N, i1 %cond.0, i1 %cond.1
    ) {
      entry:
        br label %loop

      loop:
        %result.0 = phi i64 [ %default_val, %entry ], [ %result.3, %for.inc ]
        %idx = phi i64 [ 0, %entry ], [ %inc, %for.inc ]
        br i1 %cond.0, label %outer.if.then, label %if.else

      outer.if.then:
        br i1 %cond.1, label %inner.if.then.0, label %inner.if.end.0

      inner.if.then.0:
        br label %inner.if.end.0

      inner.if.end.0:
        %result.1 = phi i64
          [ %v1, %inner.if.then.0 ], [ %result.0, %outer.if.then ]
        br label %for.inc

      if.else:
        br i1 %cond.1, label %inner.if.then.1, label %inner.if.end.1

      inner.if.then.1:
        br label %inner.if.end.1

      inner.if.end.1:
        %result.2 = phi i64 [ %v2, %inner.if.then.1 ], [ %result.0, %if.else ]
        br label %for.inc

      for.inc:
        %result.3 = phi i64
          [ %result.1, %inner.if.end.0 ], [ %result.2, %inner.if.end.1 ]
        %inc = add nsw i64 %idx, 1
        %cmp = icmp slt i64 %idx, %N
        br i1 %cmp, label  %loop, label %exit

      exit:
        ret i64 %result.3
    })");

  runWithLoopInfoAndSE(*M, "unsupported_find_last_phi",
                       [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
                         Function::iterator FI = F.begin();
                         // First basic block is entry - skip it.
                         BasicBlock *Header = &*(++FI);
                         assert(Header->getName() == "loop");
                         Loop *L = LI.getLoopFor(Header);
                         EXPECT_NE(L, nullptr);
                         BasicBlock::iterator BBI = Header->begin();
                         PHINode *Phi = dyn_cast<PHINode>(&*BBI);
                         EXPECT_NE(Phi, nullptr);
                         EXPECT_EQ(Phi->getName(), "result.0");
                         RecurrenceDescriptor Rdx;
                         bool IsRdxPhi =
                             RecurrenceDescriptor::isReductionPHI(Phi, L, Rdx);
                         EXPECT_FALSE(IsRdxPhi);
                       });
}

// Make sure isReductionPHI doesn't crash when SE is not passed to it.
TEST(IVDescriptorsTest, InvariantStoreNoSCEV) {
  // Parse the module.
  LLVMContext Context;

  std::unique_ptr<Module> M = parseIR(Context, R"(
    define void @smax_with_invariant_store_user(ptr noalias %src, ptr %dst, i64 %n) {
    entry:
      br label %loop

    loop:
      %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
      %max = phi i32 [ 0, %entry ], [ %max.next, %loop ]
      %gep.src = getelementptr inbounds i32, ptr %src, i64 %iv
      %l = load i32, ptr %gep.src, align 4
      %max.next = tail call i32 @llvm.smax.i32(i32 %max, i32 %l)
      store i32 %max.next, ptr %dst, align 4
      %iv.next = add i64 %iv, 1
      %ec = icmp eq i64 %iv, %n
      br i1 %ec, label %exit, label %loop

    exit:
      ret void
    })");

  runWithLoopInfoAndSE(*M, "smax_with_invariant_store_user",
                       [&](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
                         Function::iterator FI = F.begin();
                         // First basic block is entry - skip it.
                         BasicBlock *Header = &*(++FI);
                         assert(Header->getName() == "loop");
                         Loop *L = LI.getLoopFor(Header);
                         EXPECT_NE(L, nullptr);
                         BasicBlock::iterator BBI = Header->begin();
                         ++BBI;
                         PHINode *Phi = dyn_cast<PHINode>(&*BBI);
                         EXPECT_NE(Phi, nullptr);
                         EXPECT_EQ(Phi->getName(), "max");
                         RecurrenceDescriptor Rdx;
                         bool IsRdxPhi =
                             RecurrenceDescriptor::isReductionPHI(Phi, L, Rdx);
                         EXPECT_FALSE(IsRdxPhi);
                       });
}