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[dfsan] Introduce further optimization to reduce the number of union queries.

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Specifically, do not compute a union if it is statically known that one
shadow set subsumes the other.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213100 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2014-07-15 22:13:19 +00:00
parent 427c5cb4f9
commit 110748bbb4
2 changed files with 51 additions and 4 deletions
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36
lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
View File

@ -63,7 +63,10 @@
#include "llvm/Support/SpecialCaseList.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <iterator>
#include <set>
#include <utility>
using namespace llvm;
@ -284,6 +287,7 @@ struct DFSanFunction {
};
DenseMap<std::pair<Value *, Value *>, CachedCombinedShadow>
CachedCombinedShadows;
DenseMap<Value *, std::set<Value *>> ShadowElements;
DFSanFunction(DataFlowSanitizer &DFS, Function *F, bool IsNativeABI)
: DFS(DFS), F(F), IA(DFS.getInstrumentedABI()),
@ -892,6 +896,24 @@ Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
if (V1 == V2)
return V1;
auto V1Elems = ShadowElements.find(V1);
auto V2Elems = ShadowElements.find(V2);
if (V1Elems != ShadowElements.end() && V2Elems != ShadowElements.end()) {
if (std::includes(V1Elems->second.begin(), V1Elems->second.end(),
V2Elems->second.begin(), V2Elems->second.end())) {
return V1;
} else if (std::includes(V2Elems->second.begin(), V2Elems->second.end(),
V1Elems->second.begin(), V1Elems->second.end())) {
return V2;
}
} else if (V1Elems != ShadowElements.end()) {
if (V1Elems->second.count(V2))
return V1;
} else if (V2Elems != ShadowElements.end()) {
if (V2Elems->second.count(V1))
return V2;
}
auto Key = std::make_pair(V1, V2);
if (V1 > V2)
std::swap(Key.first, Key.second);
@ -917,6 +939,20 @@ Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
CCS.Block = Tail;
CCS.Shadow = Phi;
std::set<Value *> UnionElems;
if (V1Elems != ShadowElements.end()) {
UnionElems = V1Elems->second;
} else {
UnionElems.insert(V1);
}
if (V2Elems != ShadowElements.end()) {
UnionElems.insert(V2Elems->second.begin(), V2Elems->second.end());
} else {
UnionElems.insert(V2);
}
ShadowElements[Phi] = std::move(UnionElems);
return Phi;
}

19
test/Instrumentation/DataFlowSanitizer/union.ll
View File

@ -8,10 +8,10 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
; CHECK-LABEL: @"dfs$f"
define void @f(i32 %x, i32 %y) {
; CHECK: __dfsan_union
; CHECK: call{{.*}}__dfsan_union
%xay = add i32 %x, %y
store i32 %xay, i32* @a
; CHECK-NOT: __dfsan_union
; CHECK-NOT: call{{.*}}__dfsan_union
%xmy = mul i32 %x, %y
store i32 %xmy, i32* @b
ret void
@ -25,13 +25,13 @@ define void @g(i1 %p, i32 %x, i32 %y) {
br i1 %p, label %l1, label %l2
l1:
; CHECK: __dfsan_union
; CHECK: call{{.*}}__dfsan_union
%xay = add i32 %x, %y
store i32 %xay, i32* @a
br label %l3
l2:
; CHECK: __dfsan_union
; CHECK: call{{.*}}__dfsan_union
%xmy = mul i32 %x, %y
store i32 %xmy, i32* @b
br label %l3
@ -39,3 +39,14 @@ l2:
l3:
ret void
}
; In this case, we know that the label for %xayax subsumes the label for %xay.
; CHECK-LABEL: @"dfs$h"
define i32 @h(i32 %x, i32 %y) {
; CHECK: call{{.*}}__dfsan_union
%xay = add i32 %x, %y
; CHECK-NOT: call{{.*}}__dfsan_union
%xayax = add i32 %xay, %x
ret i32 %xayax
}