[llvm] [X86] Stop adding liveins for virtual registers in emitStackProbeInlineWindowsCoreCLR64. (PR #106828)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/106828

In the livein interface, the register goes through a MCPhysReg which is uint16_t. This causes the virtual register bit to be dropped making it alias to some nonsense physical register.

Found by llvm/test/CodeGen/X86/win_coreclr_chkstk.ll after replacing the MCPhysReg with MCRegister.

>From 67aae0049c694e3619909d440500dc360ae74c51 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Fri, 30 Aug 2024 22:47:03 -0700
Subject: [PATCH] [X86] Stop adding liveins for virtual registers in
 emitStackProbeInlineWindowsCoreCLR64.

In the livein interface, the register goes through a MCPhysReg which
is uint16_t. This causes the virtual register bit to be dropped making
it alias to some nonsense physical register.

Found by llvm/test/CodeGen/X86/win_coreclr_chkstk.ll after replacing
the MCPhysReg with MCRegister.
---
 llvm/lib/Target/X86/X86FrameLowering.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 43a3219f789c4a..39ccf22e580ade 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -1037,7 +1037,8 @@ void X86FrameLowering::emitStackProbeInlineWindowsCoreCLR64(
       .addImm(X86::COND_AE);
 
   // Add code to roundMBB to round the final stack pointer to a page boundary.
-  RoundMBB->addLiveIn(FinalReg);
+  if (InProlog)
+    RoundMBB->addLiveIn(FinalReg);
   BuildMI(RoundMBB, DL, TII.get(X86::AND64ri32), RoundedReg)
       .addReg(FinalReg)
       .addImm(PageMask);
@@ -1054,7 +1055,8 @@ void X86FrameLowering::emitStackProbeInlineWindowsCoreCLR64(
         .addMBB(LoopMBB);
   }
 
-  LoopMBB->addLiveIn(JoinReg);
+  if (InProlog)
+    LoopMBB->addLiveIn(JoinReg);
   addRegOffset(BuildMI(LoopMBB, DL, TII.get(X86::LEA64r), ProbeReg), JoinReg,
                false, -PageSize);
 
@@ -1067,7 +1069,8 @@ void X86FrameLowering::emitStackProbeInlineWindowsCoreCLR64(
       .addReg(0)
       .addImm(0);
 
-  LoopMBB->addLiveIn(RoundedReg);
+  if (InProlog)
+    LoopMBB->addLiveIn(RoundedReg);
   BuildMI(LoopMBB, DL, TII.get(X86::CMP64rr))
       .addReg(RoundedReg)
       .addReg(ProbeReg);
@@ -1091,7 +1094,8 @@ void X86FrameLowering::emitStackProbeInlineWindowsCoreCLR64(
 
   // Now that the probing is done, add code to continueMBB to update
   // the stack pointer for real.
-  ContinueMBB->addLiveIn(SizeReg);
+  if (InProlog)
+    ContinueMBB->addLiveIn(SizeReg);
   BuildMI(*ContinueMBB, ContinueMBBI, DL, TII.get(X86::SUB64rr), X86::RSP)
       .addReg(X86::RSP)
       .addReg(SizeReg);