RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2025-02-19 02:08:06 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Disable coverage opt-out for strong postdominator blocks.

Browse Source 
Coverage instrumentation has an optimization not to instrument extra
blocks, if the pass is already "accounted for" by a
successor/predecessor basic block.
However (https://github.com/google/sanitizers/issues/783) this
reasoning may become circular, which stops valid paths from having
coverage.
In the worst case this can cause fuzzing to stop working entirely.

This change simplifies logic to something which trivially can not have
such circular reasoning, as losing valid paths does not seem like a
good trade-off for a ~15% decrease in the # of instrumented basic blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303698 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
George Karpenkov 2017-05-23 21:58:54 +00:00
parent f226a627f9
commit fe601fedc1
2 changed files with 29 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
lib/Transforms/Instrumentation/SanitizerCoverage.cpp
View File

@ -31,7 +31,6 @@
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DataLayout.h"
@ -169,7 +168,6 @@ public:
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<PostDominatorTreeWrapperPass>();
}
private:
@ -367,23 +365,8 @@ static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
return true;
}
// True if block has predecessors and it postdominates all of them.
static bool isFullPostDominator(const BasicBlock *BB,
const PostDominatorTree *PDT) {
if (pred_begin(BB) == pred_end(BB))
return false;
for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
if (!PDT->dominates(BB, PRED))
return false;
}
return true;
}
static bool shouldInstrumentBlock(const Function &F, const BasicBlock *BB,
const DominatorTree *DT,
const PostDominatorTree *PDT,
const SanitizerCoverageOptions &Options) {
// Don't insert coverage for unreachable blocks: we will never call
// __sanitizer_cov() for them, so counting them in
@ -401,7 +384,7 @@ static bool shouldInstrumentBlock(const Function &F, const BasicBlock *BB,
if (Options.NoPrune || &F.getEntryBlock() == BB)
return true;
return !(isFullDominator(BB, DT) || isFullPostDominator(BB, PDT));
return !isFullDominator(BB, DT);
}
bool SanitizerCoverageModule::runOnFunction(Function &F) {
@ -433,11 +416,9 @@ bool SanitizerCoverageModule::runOnFunction(Function &F) {
const DominatorTree *DT =
&getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
const PostDominatorTree *PDT =
&getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
for (auto &BB : F) {
if (shouldInstrumentBlock(F, &BB, DT, PDT, Options))
if (shouldInstrumentBlock(F, &BB, DT, Options))
BlocksToInstrument.push_back(&BB);
for (auto &Inst : BB) {
if (Options.IndirectCalls) {
@ -719,7 +700,6 @@ INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
"ModulePass",
false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
"SanitizerCoverage: TODO."
"ModulePass",

27
test/Instrumentation/SanitizerCoverage/chains.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: opt < %s -sancov -sanitizer-coverage-level=4 -sanitizer-coverage-trace-pc -sanitizer-coverage-prune-blocks=1 -S | FileCheck %s
define i32 @blah(i32) #0 {
%2 = icmp sgt i32 %0, 1
br i1 %2, label %branch, label %exit
; CHECK: call void @__sanitizer_cov_trace_pc()
branch:
br label %pos2
; CHECK-LABEL: branch:
; CHECK-NOT: call void @__sanitizer_cov_trace_pc()
pos2:
br label %pos3
; CHECK-LABEL: pos2:
; CHECK-NOT: call void @__sanitizer_cov_trace_pc()
pos3:
br label %pos4
; CHECK-LABEL: pos3:
; CHECK-NOT: call void @__sanitizer_cov_trace_pc()
pos4:
ret i32 0
; CHECK-LABEL: pos4:
; CHECK: call void @__sanitizer_cov_trace_pc()
exit:
ret i32 0
; CHECK-LABEL: exit:
; CHECK: call void @__sanitizer_cov_trace_pc()
}