From 6f8fc217eaa12bf657be1c6468ed9938d10168b3 Mon Sep 17 00:00:00 2001
From: Dimitry Andric <dim@FreeBSD.org>
Date: Thu, 27 Jan 2022 23:06:42 +0100
Subject: Vendor import of llvm-project main
 llvmorg-14-init-17616-g024a1fab5c35.

---
 llvm/lib/CodeGen/RegisterScavenging.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'llvm/lib/CodeGen/RegisterScavenging.cpp')

diff --git a/llvm/lib/CodeGen/RegisterScavenging.cpp b/llvm/lib/CodeGen/RegisterScavenging.cpp
index c0a07ec4c91d..424ad7419165 100644
--- a/llvm/lib/CodeGen/RegisterScavenging.cpp
+++ b/llvm/lib/CodeGen/RegisterScavenging.cpp
@@ -533,6 +533,22 @@ Register RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
         Candidates.reset(*AI);
   }
 
+  // If we have already scavenged some registers, remove them from the
+  // candidates. If we end up recursively calling eliminateFrameIndex, we don't
+  // want to be clobbering previously scavenged registers or their associated
+  // stack slots.
+  for (ScavengedInfo &SI : Scavenged) {
+    if (SI.Reg) {
+      if (isRegUsed(SI.Reg)) {
+        LLVM_DEBUG(
+          dbgs() << "Removing " << printReg(SI.Reg, TRI) <<
+          " from scavenging candidates since it was already scavenged\n");
+        for (MCRegAliasIterator AI(SI.Reg, TRI, true); AI.isValid(); ++AI)
+          Candidates.reset(*AI);
+      }
+    }
+  }
+
   // Try to find a register that's unused if there is one, as then we won't
   // have to spill.
   BitVector Available = getRegsAvailable(RC);
@@ -553,6 +569,12 @@ Register RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
   if (!AllowSpill)
     return 0;
 
+#ifndef NDEBUG
+  for (ScavengedInfo &SI : Scavenged) {
+    assert(SI.Reg != SReg && "scavenged a previously scavenged register");
+  }
+#endif
+
   ScavengedInfo &Scavenged = spill(SReg, *RC, SPAdj, I, UseMI);
   Scavenged.Restore = &*std::prev(UseMI);
 
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