Revert "[SystemZFrameLowering] Don't overrwrite R1D (backchain) when probing."

Temporarily reverted.

This reverts commit ea475c77ff9eab1de7d44684c8fb453b39f70081.

1 files changed, 21 insertions, 31 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index 0bfab12..57529c8 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -488,6 +488,15 @@ void SystemZFrameLowering::emitPrologue(MachineFunction &MF,
   MFFrame.setStackSize(StackSize);
 
   if (StackSize) {
+    // Determine if we want to store a backchain.
+    bool StoreBackchain = MF.getFunction().hasFnAttribute("backchain");
+
+    // If we need backchain, save current stack pointer.  R1 is free at this
+    // point.
+    if (StoreBackchain)
+      BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::LGR))
+        .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
+
     // Allocate StackSize bytes.
     int64_t Delta = -int64_t(StackSize);
     const unsigned ProbeSize = TLI.getStackProbeSize(MF);
@@ -503,23 +512,18 @@ void SystemZFrameLowering::emitPrologue(MachineFunction &MF,
         .addImm(StackSize);
     }
     else {
-      bool StoreBackchain = MF.getFunction().hasFnAttribute("backchain");
-      // If we need backchain, save current stack pointer.  R1 is free at
-      // this point.
-      if (StoreBackchain)
-        BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::LGR))
-          .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
       emitIncrement(MBB, MBBI, DL, SystemZ::R15D, Delta, ZII);
       buildCFAOffs(MBB, MBBI, DL, SPOffsetFromCFA + Delta, ZII);
-      if (StoreBackchain) {
-        // The back chain is stored topmost with packed-stack.
-        int Offset = usePackedStack(MF) ? SystemZMC::CallFrameSize - 8 : 0;
-        BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::STG))
-          .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D)
-          .addImm(Offset).addReg(0);
-      }
     }
     SPOffsetFromCFA += Delta;
+
+    if (StoreBackchain) {
+      // The back chain is stored topmost with packed-stack.
+      int Offset = usePackedStack(MF) ? SystemZMC::CallFrameSize - 8 : 0;
+      BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::STG))
+        .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D)
+        .addImm(Offset).addReg(0);
+    }
   }
 
   if (HasFP) {
@@ -664,11 +668,6 @@ void SystemZFrameLowering::inlineStackProbe(MachineFunction &MF,
       .addMemOperand(MMO);
   };
 
-  bool StoreBackchain = MF.getFunction().hasFnAttribute("backchain");
-  if (StoreBackchain)
-    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::LGR))
-      .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
-
   if (NumFullBlocks < 3) {
     // Emit unrolled probe statements.
     for (unsigned int i = 0; i < NumFullBlocks; i++)
@@ -678,11 +677,10 @@ void SystemZFrameLowering::inlineStackProbe(MachineFunction &MF,
     uint64_t LoopAlloc = ProbeSize * NumFullBlocks;
     SPOffsetFromCFA -= LoopAlloc;
 
-    // Use R0D to hold the exit value.
-    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::LGR), SystemZ::R0D)
+    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::LGR), SystemZ::R1D)
       .addReg(SystemZ::R15D);
-    buildDefCFAReg(*MBB, MBBI, DL, SystemZ::R0D, ZII);
-    emitIncrement(*MBB, MBBI, DL, SystemZ::R0D, -int64_t(LoopAlloc), ZII);
+    buildDefCFAReg(*MBB, MBBI, DL, SystemZ::R1D, ZII);
+    emitIncrement(*MBB, MBBI, DL, SystemZ::R1D, -int64_t(LoopAlloc), ZII);
     buildCFAOffs(*MBB, MBBI, DL, -int64_t(SystemZMC::CallFrameSize + LoopAlloc),
                  ZII);
 
@@ -695,7 +693,7 @@ void SystemZFrameLowering::inlineStackProbe(MachineFunction &MF,
     MBB = LoopMBB;
     allocateAndProbe(*MBB, MBB->end(), ProbeSize, false/*EmitCFI*/);
     BuildMI(*MBB, MBB->end(), DL, ZII->get(SystemZ::CLGR))
-      .addReg(SystemZ::R15D).addReg(SystemZ::R0D);
+      .addReg(SystemZ::R15D).addReg(SystemZ::R1D);
     BuildMI(*MBB, MBB->end(), DL, ZII->get(SystemZ::BRC))
       .addImm(SystemZ::CCMASK_ICMP).addImm(SystemZ::CCMASK_CMP_GT).addMBB(MBB);
 
@@ -710,14 +708,6 @@ void SystemZFrameLowering::inlineStackProbe(MachineFunction &MF,
   if (Residual)
     allocateAndProbe(*MBB, MBBI, Residual, true/*EmitCFI*/);
 
-  if (StoreBackchain) {
-    // The back chain is stored topmost with packed-stack.
-    int Offset = usePackedStack(MF) ? SystemZMC::CallFrameSize - 8 : 0;
-    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::STG))
-      .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D)
-      .addImm(Offset).addReg(0);
-  }
-
   StackAllocMI->eraseFromParent();
 }