[llvm] r328214 - [SimplifyCFG] Create attribute for fuzzing-specific optimizations.
Matt Morehouse via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 22 10:07:51 PDT 2018
Author: morehouse
Date: Thu Mar 22 10:07:51 2018
New Revision: 328214
URL: http://llvm.org/viewvc/llvm-project?rev=328214&view=rev
Log:
[SimplifyCFG] Create attribute for fuzzing-specific optimizations.
Summary:
When building with libFuzzer, converting control flow to selects or
obscuring the original operands of CMPs reduces the effectiveness of
libFuzzer's heuristics.
This patch provides an attribute to disable or modify certain optimizations
for optimal fuzzing signal.
Provides a less aggressive alternative to https://reviews.llvm.org/D44057.
Reviewers: vitalybuka, davide, arsenm, hfinkel
Reviewed By: vitalybuka
Subscribers: junbuml, mehdi_amini, wdng, javed.absar, hiraditya, llvm-commits, kcc
Differential Revision: https://reviews.llvm.org/D44232
Added:
llvm/trunk/test/Transforms/SimplifyCFG/opt-for-fuzzing.ll
Modified:
llvm/trunk/include/llvm/Bitcode/LLVMBitCodes.h
llvm/trunk/include/llvm/IR/Attributes.td
llvm/trunk/lib/AsmParser/LLLexer.cpp
llvm/trunk/lib/AsmParser/LLParser.cpp
llvm/trunk/lib/AsmParser/LLToken.h
llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp
llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/trunk/lib/IR/Attributes.cpp
llvm/trunk/lib/IR/Verifier.cpp
llvm/trunk/lib/Transforms/IPO/ForceFunctionAttrs.cpp
llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
Modified: llvm/trunk/include/llvm/Bitcode/LLVMBitCodes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Bitcode/LLVMBitCodes.h?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Bitcode/LLVMBitCodes.h (original)
+++ llvm/trunk/include/llvm/Bitcode/LLVMBitCodes.h Thu Mar 22 10:07:51 2018
@@ -588,6 +588,7 @@ enum AttributeKindCodes {
ATTR_KIND_STRICT_FP = 54,
ATTR_KIND_SANITIZE_HWADDRESS = 55,
ATTR_KIND_NOCF_CHECK = 56,
+ ATTR_KIND_OPT_FOR_FUZZING = 57,
};
enum ComdatSelectionKindCodes {
Modified: llvm/trunk/include/llvm/IR/Attributes.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/Attributes.td?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/Attributes.td (original)
+++ llvm/trunk/include/llvm/IR/Attributes.td Thu Mar 22 10:07:51 2018
@@ -112,6 +112,9 @@ def NoCfCheck : EnumAttr<"nocf_check">;
/// Function doesn't unwind stack.
def NoUnwind : EnumAttr<"nounwind">;
+/// Select optimizations for best fuzzing signal.
+def OptForFuzzing : EnumAttr<"optforfuzzing">;
+
/// opt_size.
def OptimizeForSize : EnumAttr<"optsize">;
Modified: llvm/trunk/lib/AsmParser/LLLexer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLLexer.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/AsmParser/LLLexer.cpp (original)
+++ llvm/trunk/lib/AsmParser/LLLexer.cpp Thu Mar 22 10:07:51 2018
@@ -650,6 +650,7 @@ lltok::Kind LLLexer::LexIdentifier() {
KEYWORD(noreturn);
KEYWORD(nocf_check);
KEYWORD(nounwind);
+ KEYWORD(optforfuzzing);
KEYWORD(optnone);
KEYWORD(optsize);
KEYWORD(readnone);
Modified: llvm/trunk/lib/AsmParser/LLParser.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLParser.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/AsmParser/LLParser.cpp (original)
+++ llvm/trunk/lib/AsmParser/LLParser.cpp Thu Mar 22 10:07:51 2018
@@ -1134,6 +1134,8 @@ bool LLParser::ParseFnAttributeValuePair
case lltok::kw_nocf_check: B.addAttribute(Attribute::NoCfCheck); break;
case lltok::kw_norecurse: B.addAttribute(Attribute::NoRecurse); break;
case lltok::kw_nounwind: B.addAttribute(Attribute::NoUnwind); break;
+ case lltok::kw_optforfuzzing:
+ B.addAttribute(Attribute::OptForFuzzing); break;
case lltok::kw_optnone: B.addAttribute(Attribute::OptimizeNone); break;
case lltok::kw_optsize: B.addAttribute(Attribute::OptimizeForSize); break;
case lltok::kw_readnone: B.addAttribute(Attribute::ReadNone); break;
@@ -1471,6 +1473,7 @@ bool LLParser::ParseOptionalParamAttrs(A
case lltok::kw_noreturn:
case lltok::kw_nocf_check:
case lltok::kw_nounwind:
+ case lltok::kw_optforfuzzing:
case lltok::kw_optnone:
case lltok::kw_optsize:
case lltok::kw_returns_twice:
@@ -1565,6 +1568,7 @@ bool LLParser::ParseOptionalReturnAttrs(
case lltok::kw_noreturn:
case lltok::kw_nocf_check:
case lltok::kw_nounwind:
+ case lltok::kw_optforfuzzing:
case lltok::kw_optnone:
case lltok::kw_optsize:
case lltok::kw_returns_twice:
Modified: llvm/trunk/lib/AsmParser/LLToken.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLToken.h?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/AsmParser/LLToken.h (original)
+++ llvm/trunk/lib/AsmParser/LLToken.h Thu Mar 22 10:07:51 2018
@@ -201,6 +201,7 @@ enum Kind {
kw_noreturn,
kw_nocf_check,
kw_nounwind,
+ kw_optforfuzzing,
kw_optnone,
kw_optsize,
kw_readnone,
Modified: llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp (original)
+++ llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp Thu Mar 22 10:07:51 2018
@@ -1161,6 +1161,7 @@ static uint64_t getRawAttributeMask(Attr
case Attribute::StrictFP: return 1ULL << 55;
case Attribute::SanitizeHWAddress: return 1ULL << 56;
case Attribute::NoCfCheck: return 1ULL << 57;
+ case Attribute::OptForFuzzing: return 1ULL << 58;
case Attribute::Dereferenceable:
llvm_unreachable("dereferenceable attribute not supported in raw format");
break;
@@ -1343,6 +1344,8 @@ static Attribute::AttrKind getAttrFromCo
return Attribute::NoCfCheck;
case bitc::ATTR_KIND_NO_UNWIND:
return Attribute::NoUnwind;
+ case bitc::ATTR_KIND_OPT_FOR_FUZZING:
+ return Attribute::OptForFuzzing;
case bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE:
return Attribute::OptimizeForSize;
case bitc::ATTR_KIND_OPTIMIZE_NONE:
Modified: llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp (original)
+++ llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp Thu Mar 22 10:07:51 2018
@@ -642,6 +642,8 @@ static uint64_t getAttrKindEncoding(Attr
return bitc::ATTR_KIND_NOCF_CHECK;
case Attribute::NoUnwind:
return bitc::ATTR_KIND_NO_UNWIND;
+ case Attribute::OptForFuzzing:
+ return bitc::ATTR_KIND_OPT_FOR_FUZZING;
case Attribute::OptimizeForSize:
return bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE;
case Attribute::OptimizeNone:
Modified: llvm/trunk/lib/IR/Attributes.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Attributes.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Attributes.cpp (original)
+++ llvm/trunk/lib/IR/Attributes.cpp Thu Mar 22 10:07:51 2018
@@ -305,6 +305,8 @@ std::string Attribute::getAsString(bool
return "norecurse";
if (hasAttribute(Attribute::NoUnwind))
return "nounwind";
+ if (hasAttribute(Attribute::OptForFuzzing))
+ return "optforfuzzing";
if (hasAttribute(Attribute::OptimizeNone))
return "optnone";
if (hasAttribute(Attribute::OptimizeForSize))
Modified: llvm/trunk/lib/IR/Verifier.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Verifier.cpp (original)
+++ llvm/trunk/lib/IR/Verifier.cpp Thu Mar 22 10:07:51 2018
@@ -1430,6 +1430,7 @@ static bool isFuncOnlyAttr(Attribute::At
case Attribute::Builtin:
case Attribute::NoBuiltin:
case Attribute::Cold:
+ case Attribute::OptForFuzzing:
case Attribute::OptimizeNone:
case Attribute::JumpTable:
case Attribute::Convergent:
Modified: llvm/trunk/lib/Transforms/IPO/ForceFunctionAttrs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/ForceFunctionAttrs.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/ForceFunctionAttrs.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/ForceFunctionAttrs.cpp Thu Mar 22 10:07:51 2018
@@ -45,6 +45,7 @@ static Attribute::AttrKind parseAttrKind
.Case("nocf_check", Attribute::NoCfCheck)
.Case("norecurse", Attribute::NoRecurse)
.Case("nounwind", Attribute::NoUnwind)
+ .Case("optforfuzzing", Attribute::OptForFuzzing)
.Case("optnone", Attribute::OptimizeNone)
.Case("optsize", Attribute::OptimizeForSize)
.Case("readnone", Attribute::ReadNone)
Modified: llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp Thu Mar 22 10:07:51 2018
@@ -684,6 +684,7 @@ Function *CodeExtractor::constructFuncti
case Attribute::NonLazyBind:
case Attribute::NoRedZone:
case Attribute::NoUnwind:
+ case Attribute::OptForFuzzing:
case Attribute::OptimizeNone:
case Attribute::OptimizeForSize:
case Attribute::SafeStack:
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=328214&r1=328213&r2=328214&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Mar 22 10:07:51 2018
@@ -2273,6 +2273,10 @@ static bool FoldTwoEntryPHINode(PHINode
// dependence information for this check, but simplifycfg can't keep it up
// to date, and this catches most of the cases we care about anyway.
BasicBlock *BB = PN->getParent();
+ const Function *Fn = BB->getParent();
+ if (Fn && Fn->hasFnAttribute(Attribute::OptForFuzzing))
+ return false;
+
BasicBlock *IfTrue, *IfFalse;
Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
if (!IfCond ||
@@ -5799,6 +5803,9 @@ static BasicBlock *allPredecessorsComeFr
bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
BasicBlock *BB = BI->getParent();
+ const Function *Fn = BB->getParent();
+ if (Fn && Fn->hasFnAttribute(Attribute::OptForFuzzing))
+ return false;
// Conditional branch
if (isValueEqualityComparison(BI)) {
Added: llvm/trunk/test/Transforms/SimplifyCFG/opt-for-fuzzing.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/opt-for-fuzzing.ll?rev=328214&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/opt-for-fuzzing.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/opt-for-fuzzing.ll Thu Mar 22 10:07:51 2018
@@ -0,0 +1,49 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+define i32 @foo(i32 %x) optforfuzzing {
+entry:
+ %x.addr = alloca i32, align 4
+ store i32 %x, i32* %x.addr, align 4
+ %0 = load i32, i32* %x.addr, align 4
+ %cmp = icmp sgt i32 %0, 16
+ br i1 %cmp, label %land.rhs, label %land.end
+
+land.rhs:
+ %1 = load i32, i32* %x.addr, align 4
+ %cmp1 = icmp slt i32 %1, 32
+ br label %land.end
+
+land.end:
+ %2 = phi i1 [ false, %entry ], [ %cmp1, %land.rhs ]
+ %conv = zext i1 %2 to i32
+ ret i32 %conv
+
+; CHECK-LABEL: define i32 @foo(i32 %x)
+; CHECK: br i1 %cmp, label %land.rhs, label %land.end
+; CHECK-LABEL: land.rhs:
+; CHECK: br label %land.end
+; CHECK-LABEL: land.end:
+; CHECK: phi {{.*}} %entry {{.*}} %land.rhs
+}
+
+define i32 @bar(i32 %x) {
+entry:
+ %x.addr = alloca i32, align 4
+ store i32 %x, i32* %x.addr, align 4
+ %0 = load i32, i32* %x.addr, align 4
+ %cmp = icmp sgt i32 %0, 16
+ br i1 %cmp, label %land.rhs, label %land.end
+
+land.rhs:
+ %1 = load i32, i32* %x.addr, align 4
+ %cmp1 = icmp slt i32 %1, 32
+ br label %land.end
+
+land.end:
+ %2 = phi i1 [ false, %entry ], [ %cmp1, %land.rhs ]
+ %conv = zext i1 %2 to i32
+ ret i32 %conv
+
+; CHECK-LABEL: define i32 @bar(i32 %x)
+; CHECK-NOT: br
+}
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