diff options
4 files changed, 123 insertions, 5 deletions
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp index ce078ab8f7b..3361883acd0 100644 --- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp +++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp @@ -545,13 +545,27 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count, BasicBlock *Header = L->getHeader(); BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator()); + + if (!LatchBR || LatchBR->isUnconditional()) { + // The loop-rotate pass can be helpful to avoid this in many cases. + LLVM_DEBUG( + dbgs() + << "Loop latch not terminated by a conditional branch.\n"); + return false; + } + unsigned ExitIndex = LatchBR->getSuccessor(0) == Header ? 1 : 0; BasicBlock *LatchExit = LatchBR->getSuccessor(ExitIndex); - // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the - // targets of the Latch be an exit block out of the loop. This needs - // to be guaranteed by the callers of UnrollRuntimeLoopRemainder. - assert(!L->contains(LatchExit) && - "one of the loop latch successors should be the exit block!"); + + if (L->contains(LatchExit)) { + // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the + // targets of the Latch be an exit block out of the loop. + LLVM_DEBUG( + dbgs() + << "One of the loop latch successors must be the exit block.\n"); + return false; + } + // These are exit blocks other than the target of the latch exiting block. SmallVector<BasicBlock *, 4> OtherExits; bool isMultiExitUnrollingEnabled = diff --git a/llvm/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll b/llvm/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll new file mode 100644 index 00000000000..6915981375a --- /dev/null +++ b/llvm/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll @@ -0,0 +1,27 @@ +; REQUIRES: asserts +; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-allow-remainder=true -unroll-count=4 + +; Make sure that the runtime unroll does not break with a non-exiting latch. +define i32 @test(i32* %a, i32* %b, i32* %c, i64 %n) { +entry: + br label %while.cond + +while.cond: ; preds = %while.body, %entry + %i.0 = phi i64 [ 0, %entry ], [ %inc, %while.body ] + %cmp = icmp slt i64 %i.0, %n + br i1 %cmp, label %while.body, label %while.end + +while.body: ; preds = %while.cond + %arrayidx = getelementptr inbounds i32, i32* %b, i64 %i.0 + %0 = load i32, i32* %arrayidx + %arrayidx1 = getelementptr inbounds i32, i32* %c, i64 %i.0 + %1 = load i32, i32* %arrayidx1 + %mul = mul nsw i32 %0, %1 + %arrayidx2 = getelementptr inbounds i32, i32* %a, i64 %i.0 + store i32 %mul, i32* %arrayidx2 + %inc = add nsw i64 %i.0, 1 + br label %while.cond + +while.end: ; preds = %while.cond + ret i32 0 +} diff --git a/llvm/unittests/Transforms/Utils/CMakeLists.txt b/llvm/unittests/Transforms/Utils/CMakeLists.txt index 13c321b38a1..785b79865dc 100644 --- a/llvm/unittests/Transforms/Utils/CMakeLists.txt +++ b/llvm/unittests/Transforms/Utils/CMakeLists.txt @@ -15,5 +15,6 @@ add_llvm_unittest(UtilsTests IntegerDivisionTest.cpp LocalTest.cpp SSAUpdaterBulkTest.cpp + UnrollLoopTest.cpp ValueMapperTest.cpp ) diff --git a/llvm/unittests/Transforms/Utils/UnrollLoopTest.cpp b/llvm/unittests/Transforms/Utils/UnrollLoopTest.cpp new file mode 100644 index 00000000000..5f7c2d62380 --- /dev/null +++ b/llvm/unittests/Transforms/Utils/UnrollLoopTest.cpp @@ -0,0 +1,76 @@ +//===- UnrollLoopTest.cpp - Unit tests for UnrollLoop ---------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Utils/UnrollLoop.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/BasicBlock.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/Support/SourceMgr.h" +#include "gtest/gtest.h" + +using namespace llvm; + +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("UnrollLoopTests", errs()); + return Mod; +} + +TEST(LoopUnrollRuntime, Latch) { + LLVMContext C; + + std::unique_ptr<Module> M = parseIR( + C, + R"(define i32 @test(i32* %a, i32* %b, i32* %c, i64 %n) { +entry: + br label %while.cond + +while.cond: ; preds = %while.body, %entry + %i.0 = phi i64 [ 0, %entry ], [ %inc, %while.body ] + %cmp = icmp slt i64 %i.0, %n + br i1 %cmp, label %while.body, label %while.end + +while.body: ; preds = %while.cond + %arrayidx = getelementptr inbounds i32, i32* %b, i64 %i.0 + %0 = load i32, i32* %arrayidx + %arrayidx1 = getelementptr inbounds i32, i32* %c, i64 %i.0 + %1 = load i32, i32* %arrayidx1 + %mul = mul nsw i32 %0, %1 + %arrayidx2 = getelementptr inbounds i32, i32* %a, i64 %i.0 + store i32 %mul, i32* %arrayidx2 + %inc = add nsw i64 %i.0, 1 + br label %while.cond + +while.end: ; preds = %while.cond + ret i32 0 +})" + ); + + auto *F = M->getFunction("test"); + DominatorTree DT(*F); + LoopInfo LI(DT); + AssumptionCache AC(*F); + TargetLibraryInfoImpl TLII; + TargetLibraryInfo TLI(TLII); + ScalarEvolution SE(*F, TLI, AC, DT, LI); + + Loop *L = *LI.begin(); + + bool PreserveLCSSA = L->isRecursivelyLCSSAForm(DT,LI); + + bool ret = UnrollRuntimeLoopRemainder(L, 4, true, false, false, &LI, &SE, &DT, &AC, PreserveLCSSA); + EXPECT_FALSE(ret); +} |
