[clang] [llvm] [RISCV] Add stack clash protection (PR #117612)

[Craig Topper via cfe-commits]

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@@ -610,22 +610,134 @@ static MCCFIInstruction createDefCFAOffset(const TargetRegisterInfo &TRI,
                                         Comment.str());
 }
 
+// Allocate stack space and probe it if necessary.
 void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
-                                       StackOffset Offset, bool EmitCFI,
-                                       unsigned CFIIndex) const {
+                                       MachineFunction &MF, uint64_t Offset,
+                                       uint64_t RealStackSize, bool EmitCFI,
+                                       bool NeedProbe,
+                                       uint64_t ProbeSize) const {
   DebugLoc DL;
   const RISCVRegisterInfo *RI = STI.getRegisterInfo();
   const RISCVInstrInfo *TII = STI.getInstrInfo();
 
-  RI->adjustReg(MBB, MBBI, DL, SPReg, SPReg, Offset, MachineInstr::FrameSetup,
+  // Simply allocate the stack if it's not big enough to require a probe.
+  if (!NeedProbe || Offset <= ProbeSize) {
+    RI->adjustReg(MBB, MBBI, DL, SPReg, SPReg, StackOffset::getFixed(-Offset),
+                  MachineInstr::FrameSetup, getStackAlign());
+
+    if (EmitCFI) {
+      // Emit ".cfi_def_cfa_offset RealStackSize"
+      unsigned CFIIndex = MF.addFrameInst(
+          MCCFIInstruction::cfiDefCfaOffset(nullptr, RealStackSize));
+      BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex)
+          .setMIFlag(MachineInstr::FrameSetup);
+    }
+
+    return;
+  }
+
+  // Unroll the probe loop depending on the number of iterations.
+  if (Offset < ProbeSize * 5) {
+    uint64_t CurrentOffset = 0;
+    bool IsRV64 = STI.hasFeature(RISCV::Feature64Bit);
----------------
topperc wrote:

STI.is64Bit()?

https://github.com/llvm/llvm-project/pull/117612