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Fully invalidate cached results when a prior query's size or 

type is insufficient for, or incompatible with, the current query.

llvm-svn: 118721
This commit is contained in:
Dan Gohman 2010-11-10 21:45:11 +00:00
parent ca52411955
commit 2e8ca44b81
2 changed files with 114 additions and 10 deletions
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33
llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -756,24 +756,37 @@ getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
NonLocalPointerInfo *CacheInfo = &Pair.first->second;
// If we already have a cache entry for this CacheKey, we may need to do some
// work to reconcile the cache entry and the current query.
if (!Pair.second) {
// If this query's Size is inconsistent with the cached one, take the
// maximum size and restart the query.
if (CacheInfo->Size != Loc.Size) {
CacheInfo->Size = std::max(CacheInfo->Size, Loc.Size);
if (CacheInfo->Size < Loc.Size) {
// The query's Size is greater than the cached one. Throw out the
// cached data and procede with the query at the greater size.
CacheInfo->Pair = BBSkipFirstBlockPair();
CacheInfo->Size = Loc.Size;
CacheInfo->NonLocalDeps.clear();
} else if (CacheInfo->Size > Loc.Size) {
// This query's Size is less than the cached one. Conservatively restart
// the query using the greater size.
return getNonLocalPointerDepFromBB(Pointer,
Loc.getWithNewSize(CacheInfo->Size),
isLoad, StartBB, Result, Visited,
SkipFirstBlock);
}
// If this query's TBAATag is inconsistent with the cached one, discard the
// tag and restart the query.
// If the query's TBAATag is inconsistent with the cached one,
// conservatively throw out the cached data and restart the query with
// no tag if needed.
if (CacheInfo->TBAATag != Loc.TBAATag) {
CacheInfo->TBAATag = 0;
return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
isLoad, StartBB, Result, Visited,
SkipFirstBlock);
if (CacheInfo->TBAATag) {
CacheInfo->Pair = BBSkipFirstBlockPair();
CacheInfo->TBAATag = 0;
CacheInfo->NonLocalDeps.clear();
}
if (Loc.TBAATag)
return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
isLoad, StartBB, Result, Visited,
SkipFirstBlock);
}
}

91
llvm/test/Analysis/TypeBasedAliasAnalysis/gvn-nonlocal-type-mismatch.ll Normal file
View File

@ -0,0 +1,91 @@
; RUN: opt -enable-tbaa -tbaa -basicaa -gvn -S < %s | FileCheck %s
target datalayout = "e-p:64:64:64"
; GVN should ignore the store to p1 to see that the load from p is
; fully redundant.
; CHECK: @yes
; CHECK: if.then:
; CHECK-NEXT: store i32 0, i32* %q
; CHECK-NEXT: ret void
define void @yes(i1 %c, i32* %p, i32* %p1, i32* %q) nounwind {
entry:
store i32 0, i32* %p, !tbaa !1
store i32 1, i32* %p1, !tbaa !2
br i1 %c, label %if.else, label %if.then
if.then:
%t = load i32* %p, !tbaa !1
store i32 %t, i32* %q
ret void
if.else:
ret void
}
; GVN should ignore the store to p1 to see that the first load from p is
; fully redundant. However, the second load uses a different type. Theoretically
; the other type could be unified with the first type, however for now, GVN
; should just be conservative.
; CHECK: @watch_out_for_type_change
; CHECK: if.then:
; CHECK: %t = load i32* %p
; CHECK: store i32 %t, i32* %q
; CHECK: ret void
; CHECK: if.else:
; CHECK: %u = load i32* %p
; CHECK: store i32 %u, i32* %q
define void @watch_out_for_type_change(i1 %c, i32* %p, i32* %p1, i32* %q) nounwind {
entry:
store i32 0, i32* %p, !tbaa !1
store i32 1, i32* %p1, !tbaa !2
br i1 %c, label %if.else, label %if.then
if.then:
%t = load i32* %p, !tbaa !4
store i32 %t, i32* %q
ret void
if.else:
%u = load i32* %p, !tbaa !3
store i32 %u, i32* %q
ret void
}
; As before, but the types are swapped. This time GVN does managed to
; eliminate one of the loads before noticing the type mismatch.
; CHECK: @watch_out_for_another_type_change
; CHECK: if.then:
; CHECK: %t = load i32* %p
; CHECK: store i32 %t, i32* %q
; CHECK: ret void
; CHECK: if.else:
; CHECK: store i32 0, i32* %q
define void @watch_out_for_another_type_change(i1 %c, i32* %p, i32* %p1, i32* %q) nounwind {
entry:
store i32 0, i32* %p, !tbaa !1
store i32 1, i32* %p1, !tbaa !2
br i1 %c, label %if.else, label %if.then
if.then:
%t = load i32* %p, !tbaa !3
store i32 %t, i32* %q
ret void
if.else:
%u = load i32* %p, !tbaa !4
store i32 %u, i32* %q
ret void
}
!0 = metadata !{}
!1 = metadata !{metadata !"red", metadata !0}
!2 = metadata !{metadata !"blu", metadata !0}
!3 = metadata !{metadata !"outer space"}
!4 = metadata !{metadata !"brick red", metadata !1}