[RISCV] Use implicit def/use of SP for PROBED_STACKALLOC*. (#139153)

Author: topperc

llvm/lib/Target/RISCV/RISCVFrameLowering.cpp

@@ -633,7 +633,6 @@ void RISCVFrameLowering::allocateAndProbeStackForRVV(
 
   // It will be expanded to a probe loop in `inlineStackProbe`.
   BuildMI(MBB, MBBI, DL, TII->get(RISCV::PROBED_STACKALLOC_RVV))
-      .addReg(SPReg)
       .addReg(TargetReg);
 
   if (EmitCFI) {
@@ -828,9 +827,7 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
   }
 
   // It will be expanded to a probe loop in `inlineStackProbe`.
-  BuildMI(MBB, MBBI, DL, TII->get(RISCV::PROBED_STACKALLOC))
-      .addReg(SPReg)
-      .addReg(TargetReg);
+  BuildMI(MBB, MBBI, DL, TII->get(RISCV::PROBED_STACKALLOC)).addReg(TargetReg);
 
   if (EmitCFI) {
     // Set the CFA register back to SP.
@@ -2433,7 +2430,7 @@ void RISCVFrameLowering::inlineStackProbe(MachineFunction &MF,
         MI->getOpcode() == RISCV::PROBED_STACKALLOC_RVV) {
       MachineBasicBlock::iterator MBBI = MI->getIterator();
       DebugLoc DL = MBB.findDebugLoc(MBBI);
-      Register TargetReg = MI->getOperand(1).getReg();
+      Register TargetReg = MI->getOperand(0).getReg();
       emitStackProbeInline(MBBI, DL, TargetReg,
                            (MI->getOpcode() == RISCV::PROBED_STACKALLOC_RVV));
       MBBI->eraseFromParent();

llvm/lib/Target/RISCV/RISCVInstrInfo.td

@@ -1518,17 +1518,18 @@ def GIAddrRegImm :
 
 /// Stack probing
 
-let hasSideEffects = 1, mayLoad = 1, mayStore = 1, isCodeGenOnly = 1 in {
+let hasSideEffects = 1, mayLoad = 1, mayStore = 1, isCodeGenOnly = 1,
+    Defs = [X2], Uses = [X2] in {
 // Probed stack allocation of a constant size, used in function prologues when
 // stack-clash protection is enabled.
-def PROBED_STACKALLOC : Pseudo<(outs GPR:$sp),
-                               (ins GPR:$target),
-                               []>,
-                               Sched<[]>;
-def PROBED_STACKALLOC_RVV : Pseudo<(outs GPR:$sp),
+def PROBED_STACKALLOC : Pseudo<(outs),
                                (ins GPR:$target),
                                []>,
                                Sched<[]>;
+def PROBED_STACKALLOC_RVV : Pseudo<(outs),
+                                   (ins GPR:$target),
+                                   []>,
+                                   Sched<[]>;
 let usesCustomInserter = 1 in
 def PROBED_STACKALLOC_DYN : Pseudo<(outs),
                                (ins GPR:$target),