[RISCV] Set RegState for the stack-clash prologue registers

[rzinsly]

Set both prologue scratch registers as InternalRead for stack-clash protection to fix the tests with LLVM_ENABLE_EXPENSIVE_CHECKS.

See buildbot failure: https://lab.llvm.org/buildbot/#/builders/16/builds/10433

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Raphael Moreira Zinsly (rzinsly)

Changes

Set both prologue scratch registers as InternalRead for stack-clash protection to fix the tests with LLVM_ENABLE_EXPENSIVE_CHECKS.

See buildbot failure: https://lab.llvm.org/buildbot/#/builders/16/builds/10433

---

Full diff: https://github.com/llvm/llvm-project/pull/119451.diff

1 Files Affected:

• (modified) llvm/lib/Target/RISCV/RISCVFrameLowering.cpp (+2-2)

diff --git a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
index 655de0b4e7eb5d..e7a477a6165606 100644
--- a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -2043,7 +2043,7 @@ static void emitStackProbeInline(MachineFunction &MF, MachineBasicBlock &MBB,
   //   SUB SP, SP, ProbeSize
   BuildMI(*LoopTestMBB, LoopTestMBB->end(), DL, TII->get(RISCV::SUB), SPReg)
       .addReg(SPReg)
-      .addReg(ScratchReg)
+      .addReg(ScratchReg, RegState::InternalRead)
       .setMIFlags(Flags);
 
   //   s[d|w] zero, 0(sp)
@@ -2057,7 +2057,7 @@ static void emitStackProbeInline(MachineFunction &MF, MachineBasicBlock &MBB,
   //   BNE SP, TargetReg, LoopTest
   BuildMI(*LoopTestMBB, LoopTestMBB->end(), DL, TII->get(RISCV::BNE))
       .addReg(SPReg)
-      .addReg(TargetReg)
+      .addReg(TargetReg, RegState::InternalRead)
       .addMBB(LoopTestMBB)
       .setMIFlags(Flags);
 

[topperc]

This is no the correct fix. This is

diff --git a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
index 655de0b4e7eb..1028149bf513 100644
--- a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -14,6 +14,7 @@
 #include "RISCVMachineFunctionInfo.h"
 #include "RISCVSubtarget.h"
 #include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/CodeGen/LivePhysRegs.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -2066,6 +2067,8 @@ static void emitStackProbeInline(MachineFunction &MF, MachineBasicBlock &MBB,
   LoopTestMBB->addSuccessor(ExitMBB);
   LoopTestMBB->addSuccessor(LoopTestMBB);
   MBB.addSuccessor(LoopTestMBB);
+  // Update liveins.
+  fullyRecomputeLiveIns({ExitMBB, LoopTestMBB});
 }

[rzinsly]

@topperc Ok, thanks for working on this, I'm closing this PR.