[llvm] [TwoAddressInstructionPass] Have visit limit be a command line value (PR #100125)

[via llvm-commits]

https://github.com/AtariDreams created https://github.com/llvm/llvm-project/pull/100125

None

>From d9fd310f971c7ede1ddab811fdf75c2cf2d2d94c Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Tue, 23 Jul 2024 09:54:20 -0400
Subject: [PATCH] [TwoAddressInstructionPass] Have visit limit be a command
 line value

---
 llvm/lib/CodeGen/TwoAddressInstructionPass.cpp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 665d57841a97b..639b3c5f0da5f 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -80,6 +80,13 @@ EnableRescheduling("twoaddr-reschedule",
                    cl::desc("Coalesce copies by rescheduling (default=true)"),
                    cl::init(true), cl::Hidden);
 
+// Limit the number of rescheduling visits to dependent instructions.
+// FIXME: Arbitrary limit to reduce compile time cost.
+static cl::opt<unsigned>
+    MaxVisits("twoaddr-visit-limit", cl::Hidden, cl::init(10),
+              cl::desc("Maximum number of rescheduling visits to dependent "
+                       "instructions (0 = no limit)"));
+
 // Limit the number of dataflow edges to traverse when evaluating the benefit
 // of commuting operands.
 static cl::opt<unsigned> MaxDataFlowEdge(
@@ -994,7 +1001,7 @@ bool TwoAddressInstructionImpl::rescheduleMIBelowKill(
     // Debug or pseudo instructions cannot be counted against the limit.
     if (OtherMI.isDebugOrPseudoInstr())
       continue;
-    if (NumVisited > 10)  // FIXME: Arbitrary limit to reduce compile time cost.
+    if (MaxVisits && NumVisited > MaxVisits)
       return false;
     ++NumVisited;
     if (OtherMI.hasUnmodeledSideEffects() || OtherMI.isCall() ||
@@ -1160,14 +1167,14 @@ bool TwoAddressInstructionImpl::rescheduleKillAboveMI(
     }
   }
 
-  // Check if the reschedule will not break depedencies.
+  // Check if the reschedule will not break dependencies.
   unsigned NumVisited = 0;
   for (MachineInstr &OtherMI :
        make_range(mi, MachineBasicBlock::iterator(KillMI))) {
     // Debug or pseudo instructions cannot be counted against the limit.
     if (OtherMI.isDebugOrPseudoInstr())
       continue;
-    if (NumVisited > 10)  // FIXME: Arbitrary limit to reduce compile time cost.
+    if (MaxVisits && NumVisited > MaxVisits)
       return false;
     ++NumVisited;
     if (OtherMI.hasUnmodeledSideEffects() || OtherMI.isCall() ||