[llvm] r291649 - [LICM] Report failing to hoist conditionally-executed loads
Adam Nemet via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 10 20:39:49 PST 2017
Author: anemet
Date: Tue Jan 10 22:39:49 2017
New Revision: 291649
URL: http://llvm.org/viewvc/llvm-project?rev=291649&view=rev
Log:
[LICM] Report failing to hoist conditionally-executed loads
These are interesting again because the user may not be aware that this
is a common reason preventing LICM.
A const is removed from an instruction pointer declaration in order to
pass it to ORE.
Differential Revision: https://reviews.llvm.org/D27940
Added:
llvm/trunk/test/Transforms/LICM/opt-remarks-conditional-load.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LICM.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=291649&r1=291648&r2=291649&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Tue Jan 10 22:39:49 2017
@@ -91,10 +91,11 @@ static bool sink(Instruction &I, const L
const Loop *CurLoop, AliasSetTracker *CurAST,
const LoopSafetyInfo *SafetyInfo,
OptimizationRemarkEmitter *ORE);
-static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
+static bool isSafeToExecuteUnconditionally(Instruction &Inst,
const DominatorTree *DT,
const Loop *CurLoop,
const LoopSafetyInfo *SafetyInfo,
+ OptimizationRemarkEmitter *ORE,
const Instruction *CtxI = nullptr);
static bool pointerInvalidatedByLoop(Value *V, uint64_t Size,
const AAMDNodes &AAInfo,
@@ -434,7 +435,7 @@ bool llvm::hoistRegion(DomTreeNode *N, A
if (CurLoop->hasLoopInvariantOperands(&I) &&
canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) &&
isSafeToExecuteUnconditionally(
- I, DT, CurLoop, SafetyInfo,
+ I, DT, CurLoop, SafetyInfo, ORE,
CurLoop->getLoopPreheader()->getTerminator()))
Changed |= hoist(I, DT, CurLoop, SafetyInfo, ORE);
}
@@ -819,15 +820,28 @@ static bool hoist(Instruction &I, const
/// Only sink or hoist an instruction if it is not a trapping instruction,
/// or if the instruction is known not to trap when moved to the preheader.
/// or if it is a trapping instruction and is guaranteed to execute.
-static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
+static bool isSafeToExecuteUnconditionally(Instruction &Inst,
const DominatorTree *DT,
const Loop *CurLoop,
const LoopSafetyInfo *SafetyInfo,
+ OptimizationRemarkEmitter *ORE,
const Instruction *CtxI) {
if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT))
return true;
- return isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo);
+ bool GuaranteedToExecute =
+ isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo);
+
+ if (!GuaranteedToExecute) {
+ auto *LI = dyn_cast<LoadInst>(&Inst);
+ if (LI && CurLoop->isLoopInvariant(LI->getPointerOperand()))
+ ORE->emit(OptimizationRemarkMissed(
+ DEBUG_TYPE, "LoadWithLoopInvariantAddressCondExecuted", LI)
+ << "failed to hoist load with loop-invariant address "
+ "because load is conditionally executed");
+ }
+
+ return GuaranteedToExecute;
}
namespace {
@@ -1016,14 +1030,14 @@ bool llvm::promoteLoopAccessesToScalars(
// If there is an non-load/store instruction in the loop, we can't promote
// it.
- if (const LoadInst *Load = dyn_cast<LoadInst>(UI)) {
+ if (LoadInst *Load = dyn_cast<LoadInst>(UI)) {
assert(!Load->isVolatile() && "AST broken");
if (!Load->isSimple())
return false;
if (!DereferenceableInPH)
DereferenceableInPH = isSafeToExecuteUnconditionally(
- *Load, DT, CurLoop, SafetyInfo, Preheader->getTerminator());
+ *Load, DT, CurLoop, SafetyInfo, ORE, Preheader->getTerminator());
} else if (const StoreInst *Store = dyn_cast<StoreInst>(UI)) {
// Stores *of* the pointer are not interesting, only stores *to* the
// pointer.
Added: llvm/trunk/test/Transforms/LICM/opt-remarks-conditional-load.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/opt-remarks-conditional-load.ll?rev=291649&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LICM/opt-remarks-conditional-load.ll (added)
+++ llvm/trunk/test/Transforms/LICM/opt-remarks-conditional-load.ll Tue Jan 10 22:39:49 2017
@@ -0,0 +1,47 @@
+; 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"
+
+; With the load from %p conditional, we can't optmize this and the remark
+; should tell us about it.
+
+define void @test(i32* %array, i32* noalias %p) {
+Entry:
+ br label %Loop
+
+Loop:
+ %j = phi i32 [ 0, %Entry ], [ %Next, %else]
+ %addr = getelementptr i32, i32* %array, i32 %j
+ %a = load i32, i32* %addr
+ %c = icmp eq i32 %a, 0
+ br i1 %c, label %then, label %else
+
+then:
+; CHECK: remark: /tmp/kk.c:2:20: failed to hoist load with loop-invariant address because load is conditionally executed
+ %b = load i32, i32* %p, !dbg !8
+ %a2 = add i32 %a, %b
+ store i32 %a2, i32* %addr
+ br label %else
+
+else:
+ %Next = add i32 %j, 1
+ %cond = icmp eq i32 %Next, 0
+ br i1 %cond, label %Out, label %Loop
+
+Out:
+ ret void
+}
+
+!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)
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