[SSP, 2/2] Create llvm.stackguard() intrinsic and lower it to LOAD_STACK_GUARD
With this change, ideally IR pass can always generate llvm.stackguard
call to get the stack guard; but for now there are still IR form stack
guard customizations around (see getIRStackGuard()). Future SSP
customization should go through LOAD_STACK_GUARD.
There is a behavior change: stack guard values are not CSEed anymore,
since we should never reuse the value in case that it has been spilled (and
corrupted). See ssp-guard-spill.ll. This also cause the change of stack
size and codegen in X86 and AArch64 test cases.
Ideally we'd like to know if the guard created in llvm.stackprotector() gets
spilled or not. If the value is spilled, discard the value and reload
stack guard; otherwise reuse the value. This can be done by teaching
register allocator to know how to rematerialize LOAD_STACK_GUARD and
force a rematerialization (which seems hard), or check for spilling in
expandPostRAPseudo. It only makes sense when the stack guard is a global
variable, which requires more instructions to load. Anyway, this seems to go out
of the scope of the current patch.
llvm-svn: 266806
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 591361e..0f8d8a5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -465,8 +465,7 @@
class StackProtectorDescriptor {
public:
StackProtectorDescriptor()
- : ParentMBB(nullptr), SuccessMBB(nullptr), FailureMBB(nullptr),
- GuardReg(0) {}
+ : ParentMBB(nullptr), SuccessMBB(nullptr), FailureMBB(nullptr) {}
/// Returns true if all fields of the stack protector descriptor are
/// initialized implying that we should/are ready to emit a stack protector.
@@ -511,16 +510,12 @@
/// always the same.
void resetPerFunctionState() {
FailureMBB = nullptr;
- GuardReg = 0;
}
MachineBasicBlock *getParentMBB() { return ParentMBB; }
MachineBasicBlock *getSuccessMBB() { return SuccessMBB; }
MachineBasicBlock *getFailureMBB() { return FailureMBB; }
- unsigned getGuardReg() const { return GuardReg; }
- void setGuardReg(unsigned R) { GuardReg = R; }
-
private:
/// The basic block for which we are generating the stack protector.
///
@@ -539,9 +534,6 @@
/// contain a call to __stack_chk_fail().
MachineBasicBlock *FailureMBB;
- /// The virtual register holding the stack guard value.
- unsigned GuardReg;
-
/// Add a successor machine basic block to ParentMBB. If the successor mbb
/// has not been created yet (i.e. if SuccMBB = 0), then the machine basic
/// block will be created. Assign a large weight if IsLikely is true.