[llvm] [CodeGen] Remove unused -rafast-ignore-missing-defs (PR #228808)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay created https://github.com/llvm/llvm-project/pull/228808

Unused since the 2020 RegAllocFast rewrite (c8757ff3aa7d) introduced it.

>From 41436a4707f3c0d67839ee6f5b7fcd17836c3b3d Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Sat, 3 Oct 2026 19:05:51 -0700
Subject: [PATCH] [CodeGen] Remove unused -rafast-ignore-missing-defs

Unused since the 2020 RegAllocFast rewrite (c8757ff3aa7d) introduced it.
---
 llvm/lib/CodeGen/RegAllocFast.cpp | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/llvm/lib/CodeGen/RegAllocFast.cpp b/llvm/lib/CodeGen/RegAllocFast.cpp
index 467a3a614b65079..4bbf3b956b83d28 100644
--- a/llvm/lib/CodeGen/RegAllocFast.cpp
+++ b/llvm/lib/CodeGen/RegAllocFast.cpp
@@ -61,10 +61,6 @@ STATISTIC(NumStores, "Number of stores added");
 STATISTIC(NumLoads, "Number of loads added");
 STATISTIC(NumCoalesced, "Number of copies coalesced");
 
-// FIXME: Remove this switch when all testcases are fixed!
-static cl::opt<bool> IgnoreMissingDefs("rafast-ignore-missing-defs",
-                                       cl::Hidden);
-
 static RegisterRegAlloc fastRegAlloc("fast", "fast register allocator",
                                      createFastRegisterAllocator);
 
@@ -732,7 +728,7 @@ void RegAllocFastImpl::reloadAtBegin(MachineBasicBlock &MBB) {
     if (getRegUnitState(FirstUnit) == regLiveIn)
       continue;
 
-    assert((&MBB != &MBB.getParent()->front() || IgnoreMissingDefs) &&
+    assert(&MBB != &MBB.getParent()->front() &&
            "no reload in start block. Missing vreg def?");
 
     if (PrologLiveIns.count(PhysReg)) {