diff options
Diffstat (limited to 'llvm/lib/Analysis/ValueTracking.cpp')
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 09a8fbe..1eda7a7 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -89,6 +89,9 @@ using namespace llvm::PatternMatch; static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses", cl::Hidden, cl::init(20)); +/// Maximum number of instructions to check between assume and context +/// instruction. +static constexpr unsigned MaxInstrsToCheckForFree = 16; /// Returns the bitwidth of the given scalar or pointer type. For vector types, /// returns the element type's bitwidth. @@ -561,6 +564,29 @@ bool llvm::isValidAssumeForContext(const Instruction *Inv, return false; } +bool llvm::willNotFreeBetween(const Instruction *Assume, + const Instruction *CtxI) { + if (CtxI->getParent() != Assume->getParent() || !Assume->comesBefore(CtxI)) + return false; + // Make sure the current function cannot arrange for another thread to free on + // its behalf. + if (!CtxI->getFunction()->hasNoSync()) + return false; + + // Check if there are any calls between the assume and CtxI that may + // free memory. + for (const auto &[Idx, I] : + enumerate(make_range(Assume->getIterator(), CtxI->getIterator()))) { + // Limit number of instructions to walk. + if (Idx > MaxInstrsToCheckForFree) + return false; + if (const auto *CB = dyn_cast<CallBase>(&I)) + if (!CB->hasFnAttr(Attribute::NoFree)) + return false; + } + return true; +} + // TODO: cmpExcludesZero misses many cases where `RHS` is non-constant but // we still have enough information about `RHS` to conclude non-zero. For // example Pred=EQ, RHS=isKnownNonZero. cmpExcludesZero is called in loops |