[PATCH] D23076: Support for lifetime begin/end markers in the use optimizer
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llvm-commits at lists.llvm.org
Tue Aug 2 17:09:39 PDT 2016
This revision was automatically updated to reflect the committed changes.
Closed by commit rL277553: Support for lifetime begin/end markers in the MemorySSA use optimizer (authored by dannyb).
Changed prior to commit:
https://reviews.llvm.org/D23076?vs=66565&id=66598#toc
Repository:
rL LLVM
https://reviews.llvm.org/D23076
Files:
llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
llvm/trunk/test/Transforms/Util/MemorySSA/lifetime-simple.ll
Index: llvm/trunk/test/Transforms/Util/MemorySSA/lifetime-simple.ll
===================================================================
--- llvm/trunk/test/Transforms/Util/MemorySSA/lifetime-simple.ll
+++ llvm/trunk/test/Transforms/Util/MemorySSA/lifetime-simple.ll
@@ -0,0 +1,30 @@
+; RUN: opt -basicaa -print-memoryssa -verify-memoryssa -analyze < %s 2>&1 | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes='print<memoryssa>,verify<memoryssa>' -disable-output < %s 2>&1 | FileCheck %s
+; This test checks a number of things:
+; First, the lifetime markers should not clobber any uses of Q or P.
+; Second, the loads of P are MemoryUse(LiveOnEntry) due to the placement of the markers vs the loads.
+
+define i8 @test(i8* %P, i8* %Q) {
+entry:
+; CHECK: 1 = MemoryDef(liveOnEntry)
+; CHECK-NEXT: call void @llvm.lifetime.start(i64 32, i8* %P)
+ call void @llvm.lifetime.start(i64 32, i8* %P)
+; CHECK: MemoryUse(liveOnEntry)
+; CHECK-NEXT: %0 = load i8, i8* %P
+ %0 = load i8, i8* %P
+; CHECK: 2 = MemoryDef(1)
+; CHECK-NEXT: store i8 1, i8* %P
+ store i8 1, i8* %P
+; CHECK: 3 = MemoryDef(2)
+; CHECK-NEXT: call void @llvm.lifetime.end(i64 32, i8* %P)
+ call void @llvm.lifetime.end(i64 32, i8* %P)
+; CHECK: MemoryUse(liveOnEntry)
+; CHECK-NEXT: %1 = load i8, i8* %P
+ %1 = load i8, i8* %P
+; CHECK: MemoryUse(2)
+; CHECK-NEXT: %2 = load i8, i8* %Q
+ %2 = load i8, i8* %Q
+ ret i8 %1
+}
+declare void @llvm.lifetime.start(i64 %S, i8* nocapture %P) readonly
+declare void @llvm.lifetime.end(i64 %S, i8* nocapture %P)
Index: llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
+++ llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
@@ -192,13 +192,43 @@
}
};
+static bool lifetimeEndsAt(MemoryDef *MD, const MemoryLocation &Loc,
+ AliasAnalysis &AA) {
+ Instruction *Inst = MD->getMemoryInst();
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+ switch (II->getIntrinsicID()) {
+ case Intrinsic::lifetime_start:
+ case Intrinsic::lifetime_end:
+ return AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), Loc);
+ default:
+ return false;
+ }
+ }
+ return false;
+}
+
static bool instructionClobbersQuery(MemoryDef *MD,
const MemoryLocation &UseLoc,
const Instruction *UseInst,
AliasAnalysis &AA) {
Instruction *DefInst = MD->getMemoryInst();
assert(DefInst && "Defining instruction not actually an instruction");
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) {
+ // These intrinsics will show up as affecting memory, but they are just
+ // markers.
+ switch (II->getIntrinsicID()) {
+ case Intrinsic::lifetime_start:
+ case Intrinsic::lifetime_end:
+ case Intrinsic::invariant_start:
+ case Intrinsic::invariant_end:
+ case Intrinsic::assume:
+ return false;
+ default:
+ break;
+ }
+ }
+
ImmutableCallSite UseCS(UseInst);
if (UseCS) {
ModRefInfo I = AA.getModRefInfo(DefInst, UseCS);
@@ -1308,7 +1338,14 @@
}
MemoryDef *MD = cast<MemoryDef>(VersionStack[UpperBound]);
-
+ // If the lifetime of the pointer ends at this instruction, it's live on
+ // entry.
+ if (!UseMLOC.IsCall && lifetimeEndsAt(MD, UseMLOC.getLoc(), *AA)) {
+ // Reset UpperBound to liveOnEntryDef's place in the stack
+ UpperBound = 0;
+ FoundClobberResult = true;
+ break;
+ }
if (instructionClobbersQuery(MD, MU, UseMLOC, *AA)) {
FoundClobberResult = true;
break;
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