Index: clang/lib/Analysis/UninitializedValues.cpp =================================================================== --- clang/lib/Analysis/UninitializedValues.cpp +++ clang/lib/Analysis/UninitializedValues.cpp @@ -575,6 +575,28 @@ continue; } + if (AtPredExit == MayUninitialized) { + // If the predecessor's terminator is an "asm goto" that initializes + // the variable, then it won't be counted as "initialized" on the + // non-fallthrough paths. + CFGTerminator term = Pred->getTerminator(); + if (const auto *as = dyn_cast_or_null(term.getStmt())) { + const CFGBlock *fallthrough = *Pred->succ_begin(); + if (as->isAsmGoto() && + llvm::any_of(as->outputs(), [&](const Expr *output) { + return vd == findVar(output).getDecl() && + llvm::any_of(as->labels(), + [&](const AddrLabelExpr *label) { + return label->getLabel()->getStmt() == B->Label && + B != fallthrough; + }); + })) { + Use.setUninitAfterDecl(); + continue; + } + } + } + unsigned &SV = SuccsVisited[Pred->getBlockID()]; if (!SV) { // When visiting the first successor of a block, mark all NULL @@ -760,6 +782,17 @@ } } +void TransferFunctions::VisitGCCAsmStmt(GCCAsmStmt *as) { + // An "asm goto" statement is a terminator that may initialize some variables. + if (!as->isAsmGoto()) + return; + + for (const auto &o : as->outputs()) + if (const auto *VD = findVar(o).getDecl()) + if (vals[VD] != Initialized) + vals[VD] = MayUninitialized; +} + void TransferFunctions::VisitObjCMessageExpr(ObjCMessageExpr *ME) { // If the Objective-C message expression is an implicit no-return that // is not modeled in the CFG, set the tracked dataflow values to Unknown. @@ -797,6 +830,10 @@ if (Optional cs = I.getAs()) tf.Visit(const_cast(cs->getStmt())); } + CFGTerminator terminator = block->getTerminator(); + if (const auto *as = dyn_cast_or_null(terminator.getStmt())) + if (as->isAsmGoto()) + tf.Visit(as); return vals.updateValueVectorWithScratch(block); } Index: clang/test/Analysis/uninit-asm-goto.cpp =================================================================== --- /dev/null +++ clang/test/Analysis/uninit-asm-goto.cpp @@ -0,0 +1,59 @@ +// RUN: %clang_cc1 -std=c++11 -Wuninitialized -verify %s + +// test1: Expect no diagnostics +int test1(int x) { + int y; + asm goto("# %0 %1 %2" : "=r"(y) : "r"(x) : : err); + return y; + err: + return -1; +} + +int test2(int x) { + int y; // expected-warning {{variable 'y' is used uninitialized whenever its declaration is reached}} \ + // expected-note {{initialize the variable}} + if (x < 42) + asm volatile goto("testl %0, %0; testl %1, %2; jne %l3" : "+S"(x), "+D"(y) : "r"(x) :: indirect_1, indirect_2); + else + asm volatile goto("testl %0, %1; testl %2, %3; jne %l5" : "+S"(x), "+D"(y) : "r"(x), "r"(y) :: indirect_1, indirect_2); + return x + y; +indirect_1: + return -42; +indirect_2: + return y; // expected-note {{uninitialized use occurs here}} +} + +int test3(int x) { + int y; // expected-warning {{variable 'y' is used uninitialized whenever its declaration is reached}} \ + // expected-note {{initialize the variable}} + asm goto("xorl %1, %0; jmp %l2" : "=&r"(y) : "r"(x) : : fail); +normal: + y += x; + return y; + if (x) { +fail: + return y; // expected-note {{uninitialized use occurs here}} + } + return 0; +} + +int test4(int x) { + int y; // expected-warning {{variable 'y' is used uninitialized whenever its declaration is reached}} \ + // expected-note {{initialize the variable}} + goto forward; +backward: + return y; // expected-note {{uninitialized use occurs here}} +forward: + asm goto("# %0 %1 %2" : "=r"(y) : "r"(x) : : backward); + return y; +} + +// test5: Expect no diagnostics +int test5(int x) { + int y; + asm volatile goto("testl %0, %0; testl %1, %2; jne %l3" : "+S"(x), "+D"(y) : "r"(x) :: fallthrough_1, fallthrough_2); +fallthrough_1: + return y; +fallthrough_2: + return -2; +}