[PATCH] D23076: Support for lifetime begin/end markers in the use optimizer
Daniel Berlin via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 2 12:32:57 PDT 2016
dberlin updated this revision to Diff 66524.
dberlin added a comment.
- Fix bug, add test
https://reviews.llvm.org/D23076
Files:
lib/Transforms/Utils/MemorySSA.cpp
test/Transforms/Util/MemorySSA/lifetime-simple.ll
Index: test/Transforms/Util/MemorySSA/lifetime-simple.ll
===================================================================
--- /dev/null
+++ test/Transforms/Util/MemorySSA/lifetime-simple.ll
@@ -0,0 +1,23 @@
+; 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
+define i8 @test(i8* %P, i8* %Q) {
+; This checks a number of things
+; First, the lifetime markers should not clobber any uses
+; Second, the loads are of live on entry due to the placement of the markers vs the loads
+entry:
+; CHECK: 1 = MemoryDef(liveOnEntry)
+ call void @llvm.lifetime.start(i64 32, i8* %P)
+; CHECK-DAG: MemoryUse(liveOnEntry)
+ %0 = load i8, i8* %P
+; CHECK-DAG: 2 = MemoryDef(1)
+ store i8 1, i8* %P
+; CHECK-DAG: 3 = MemoryDef(2)
+ call void @llvm.lifetime.end(i64 32, i8* %P)
+; CHECK-DAG: MemoryUse(liveOnEntry)
+ %1 = load i8, i8* %P
+; CHECK-DAG: MemoryUse(2)
+ %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: lib/Transforms/Utils/MemorySSA.cpp
===================================================================
--- lib/Transforms/Utils/MemorySSA.cpp
+++ lib/Transforms/Utils/MemorySSA.cpp
@@ -170,13 +170,46 @@
}
};
+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:
+ {
+ if (AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), Loc))
+ return true;
+ }
+ 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);
@@ -1307,7 +1340,14 @@
}
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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