[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 12:12:58 PDT 2016
dberlin updated this revision to Diff 66519.
dberlin added a comment.
- Remove dead comment
https://reviews.llvm.org/D23076
Files:
lib/Transforms/Utils/MemorySSA.cpp
Index: lib/Transforms/Utils/MemorySSA.cpp
===================================================================
--- lib/Transforms/Utils/MemorySSA.cpp
+++ lib/Transforms/Utils/MemorySSA.cpp
@@ -170,13 +170,40 @@
}
};
+static bool lifetimeEndsAt(MemoryDef *MD, const MemoryLocation &Loc,
+ AliasAnalysis &AA) {
+ Instruction *Inst = MD->getMemoryInst();
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
+ if (AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), Loc))
+ return true;
+ }
+ }
+ 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>(UseInst)) {
+ // 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);
@@ -501,7 +528,7 @@
if (Current == StopAt)
return {Current, false, false};
- if (auto *MD = dyn_cast<MemoryDef>(Current))
+ if (auto *MD = dyn_cast<MemoryDef>(Current)) {
if (MSSA.isLiveOnEntryDef(MD) ||
instructionClobbersQuery(MD, Desc.Loc, Query->Inst, AA))
return {MD, true, false};
@@ -1307,7 +1334,14 @@
}
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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