[llvm] r291648 - [LICM] Report failing to hoist a load with an invariant address
Adam Nemet via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 10 20:39:45 PST 2017
Author: anemet
Date: Tue Jan 10 22:39:45 2017
New Revision: 291648
URL: http://llvm.org/viewvc/llvm-project?rev=291648&view=rev
Log:
[LICM] Report failing to hoist a load with an invariant address
These are interesting because lack of precision in alias information
could be standing in the way of this optimization.
An example is the case in the test suite that I showed in the DevMeeting
talk:
http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/MultiSource/Benchmarks/FreeBench/distray/CMakeFiles/distray.dir/html/_org_test-suite_MultiSource_Benchmarks_FreeBench_distray_distray.c.html#L236
canSinkOrHoistInst is also used from LoopSink, which does not use
opt-remarks so we need to take ORE as an optional argument.
Differential Revision: https://reviews.llvm.org/D27939
Added:
llvm/trunk/test/Transforms/LICM/opt-remarks-intervening-store.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
llvm/trunk/lib/Transforms/Scalar/LICM.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h?rev=291648&r1=291647&r2=291648&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/LoopUtils.h Tue Jan 10 22:39:45 2017
@@ -483,10 +483,11 @@ void getLoopAnalysisUsage(AnalysisUsage
/// If SafetyInfo is not null, we are checking for hoisting/sinking
/// instructions from loop body to preheader/exit. Check if the instruction
/// can execute speculatively.
-///
+/// If \p ORE is set use it to emit optimization remarks.
bool canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
Loop *CurLoop, AliasSetTracker *CurAST,
- LoopSafetyInfo *SafetyInfo);
+ LoopSafetyInfo *SafetyInfo,
+ OptimizationRemarkEmitter *ORE = nullptr);
}
#endif
Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=291648&r1=291647&r2=291648&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Tue Jan 10 22:39:45 2017
@@ -377,7 +377,7 @@ bool llvm::sinkRegion(DomTreeNode *N, Al
// operands of the instruction are loop invariant.
//
if (isNotUsedInLoop(I, CurLoop, SafetyInfo) &&
- canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo)) {
+ canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE)) {
++II;
Changed |= sink(I, LI, DT, CurLoop, CurAST, SafetyInfo, ORE);
}
@@ -432,7 +432,7 @@ bool llvm::hoistRegion(DomTreeNode *N, A
// is safe to hoist the instruction.
//
if (CurLoop->hasLoopInvariantOperands(&I) &&
- canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo) &&
+ canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) &&
isSafeToExecuteUnconditionally(
I, DT, CurLoop, SafetyInfo,
CurLoop->getLoopPreheader()->getTerminator()))
@@ -481,7 +481,8 @@ void llvm::computeLoopSafetyInfo(LoopSaf
bool llvm::canSinkOrHoistInst(Instruction &I, AAResults *AA, DominatorTree *DT,
Loop *CurLoop, AliasSetTracker *CurAST,
- LoopSafetyInfo *SafetyInfo) {
+ LoopSafetyInfo *SafetyInfo,
+ OptimizationRemarkEmitter *ORE) {
// Loads have extra constraints we have to verify before we can hoist them.
if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
if (!LI->isUnordered())
@@ -502,7 +503,17 @@ bool llvm::canSinkOrHoistInst(Instructio
AAMDNodes AAInfo;
LI->getAAMetadata(AAInfo);
- return !pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo, CurAST);
+ bool Invalidated =
+ pointerInvalidatedByLoop(LI->getOperand(0), Size, AAInfo, CurAST);
+ // Check loop-invariant address because this may also be a sinkable load
+ // whose address is not necessarily loop-invariant.
+ if (ORE && Invalidated && CurLoop->isLoopInvariant(LI->getPointerOperand()))
+ ORE->emit(OptimizationRemarkMissed(
+ DEBUG_TYPE, "LoadWithLoopInvariantAddressInvalidated", LI)
+ << "failed to move load with loop-invariant address "
+ "because the loop may invalidate its value");
+
+ return !Invalidated;
} else if (CallInst *CI = dyn_cast<CallInst>(&I)) {
// Don't sink or hoist dbg info; it's legal, but not useful.
if (isa<DbgInfoIntrinsic>(I))
Added: llvm/trunk/test/Transforms/LICM/opt-remarks-intervening-store.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/opt-remarks-intervening-store.ll?rev=291648&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LICM/opt-remarks-intervening-store.ll (added)
+++ llvm/trunk/test/Transforms/LICM/opt-remarks-intervening-store.ll Tue Jan 10 22:39:45 2017
@@ -0,0 +1,67 @@
+; RUN: opt < %s -licm -pass-remarks-missed=licm -o /dev/null 2>&1 | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' %s -o /dev/null -pass-remarks-missed=licm 2>&1 | FileCheck %s
+target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
+
+; Without the noalias on %p, we can't optmize this and the remark should tell
+; us about it.
+
+define void @test(i32* %array, i32* %p) {
+Entry:
+ br label %Loop
+
+Loop:
+ %j = phi i32 [ 0, %Entry ], [ %Next, %Loop ]
+ %addr = getelementptr i32, i32* %array, i32 %j
+ %a = load i32, i32* %addr
+; CHECK: remark: /tmp/kk.c:2:20: failed to move load with loop-invariant address because the loop may invalidate its value
+ %b = load i32, i32* %p, !dbg !8
+ %a2 = add i32 %a, %b
+ store i32 %a2, i32* %addr
+ %Next = add i32 %j, 1
+ %cond = icmp eq i32 %Next, 0
+ br i1 %cond, label %Out, label %Loop
+
+Out:
+ ret void
+}
+
+; This illustrates why we need to check loop-invariance before issuing this
+; remark.
+
+define i32 @invalidated_load_with_non_loop_invariant_address(i32* %array, i32* %array2) {
+Entry:
+ br label %Loop
+
+Loop:
+ %j = phi i32 [ 0, %Entry ], [ %Next, %Loop ]
+
+; CHECK-NOT: /tmp/kk.c:3:20: {{.*}} loop-invariant
+ %addr = getelementptr i32, i32* %array, i32 %j
+ %a = load i32, i32* %addr, !dbg !9
+
+ %addr2 = getelementptr i32, i32* %array2, i32 %j
+ store i32 %j, i32* %addr2
+
+ %Next = add i32 %j, 1
+ %cond = icmp eq i32 %Next, 0
+ br i1 %cond, label %Out, label %Loop
+
+Out:
+ %a2 = phi i32 [ %a, %Loop ]
+ ret i32 %a2
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: NoDebug, enums: !2)
+!1 = !DIFile(filename: "/tmp/kk.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"PIC Level", i32 2}
+!5 = !{!"clang version 3.9.0 "}
+!6 = distinct !DISubprogram(name: "success", scope: !1, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 2, column: 20, scope: !6)
+!9 = !DILocation(line: 3, column: 20, scope: !6)
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