[llvm] r342958 - [LoopUnroll] Add check to Latch's terminator in UnrollRuntimeLoopRemainder
David Green via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 25 03:08:48 PDT 2018
Author: dmgreen
Date: Tue Sep 25 03:08:47 2018
New Revision: 342958
URL: http://llvm.org/viewvc/llvm-project?rev=342958&view=rev
Log:
[LoopUnroll] Add check to Latch's terminator in UnrollRuntimeLoopRemainder
In this patch, I'm adding an extra check to the Latch's terminator in llvm::UnrollRuntimeLoopRemainder,
similar to how it is already done in the llvm::UnrollLoop.
The compiler would crash if this function is called with a malformed loop.
Patch by Rodrigo Caetano Rocha!
Differential Revision: https://reviews.llvm.org/D51486
Added:
llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll
llvm/trunk/unittests/Transforms/Utils/UnrollLoopTest.cpp
Modified:
llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
llvm/trunk/unittests/Transforms/Utils/CMakeLists.txt
Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp?rev=342958&r1=342957&r2=342958&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp Tue Sep 25 03:08:47 2018
@@ -545,13 +545,27 @@ bool llvm::UnrollRuntimeLoopRemainder(Lo
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 =
Added: llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll?rev=342958&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll (added)
+++ llvm/trunk/test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll Tue Sep 25 03:08:47 2018
@@ -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
+}
Modified: llvm/trunk/unittests/Transforms/Utils/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Transforms/Utils/CMakeLists.txt?rev=342958&r1=342957&r2=342958&view=diff
==============================================================================
--- llvm/trunk/unittests/Transforms/Utils/CMakeLists.txt (original)
+++ llvm/trunk/unittests/Transforms/Utils/CMakeLists.txt Tue Sep 25 03:08:47 2018
@@ -15,5 +15,6 @@ add_llvm_unittest(UtilsTests
IntegerDivisionTest.cpp
LocalTest.cpp
SSAUpdaterBulkTest.cpp
+ UnrollLoopTest.cpp
ValueMapperTest.cpp
)
Added: llvm/trunk/unittests/Transforms/Utils/UnrollLoopTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Transforms/Utils/UnrollLoopTest.cpp?rev=342958&view=auto
==============================================================================
--- llvm/trunk/unittests/Transforms/Utils/UnrollLoopTest.cpp (added)
+++ llvm/trunk/unittests/Transforms/Utils/UnrollLoopTest.cpp Tue Sep 25 03:08:47 2018
@@ -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);
+}
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