[RISCV] Remove -riscv-insert-vsetvl-strict-asserts flag (#90171)

This flag has been enabled by default for almost two years now since
1f06398, and at this stage we probably
shouldn't be falling back to the fixups.

This removes the flag so we always perform the assertion, as well as
making sure that CurInfo is always valid on exit: We shouldn't leave
emitVSETVLIs with an uninitialized VSETVLIInfo.

Author: lukel97

llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp

@@ -45,10 +45,6 @@ static cl::opt<bool> DisableInsertVSETVLPHIOpt(
     "riscv-disable-insert-vsetvl-phi-opt", cl::init(false), cl::Hidden,
     cl::desc("Disable looking through phis when inserting vsetvlis."));
 
-static cl::opt<bool> UseStrictAsserts(
-    "riscv-insert-vsetvl-strict-asserts", cl::init(true), cl::Hidden,
-    cl::desc("Enable strict assertion checking for the dataflow algorithm"));
-
 namespace {
 
 static unsigned getVLOpNum(const MachineInstr &MI) {
@@ -1432,32 +1428,14 @@ void RISCVInsertVSETVLI::emitVSETVLIs(MachineBasicBlock &MBB) {
     transferAfter(CurInfo, MI);
   }
 
-  // If we reach the end of the block and our current info doesn't match the
-  // expected info, insert a vsetvli to correct.
-  if (!UseStrictAsserts) {
-    const VSETVLIInfo &ExitInfo = BlockInfo[MBB.getNumber()].Exit;
-    if (CurInfo.isValid() && ExitInfo.isValid() && !ExitInfo.isUnknown() &&
-        CurInfo != ExitInfo) {
-      // Note there's an implicit assumption here that terminators never use
-      // or modify VL or VTYPE.  Also, fallthrough will return end().
-      auto InsertPt = MBB.getFirstInstrTerminator();
-      insertVSETVLI(MBB, InsertPt, MBB.findDebugLoc(InsertPt), ExitInfo,
-                    CurInfo);
-      CurInfo = ExitInfo;
-    }
-  }
-
-  if (UseStrictAsserts && CurInfo.isValid()) {
-    const auto &Info = BlockInfo[MBB.getNumber()];
-    if (CurInfo != Info.Exit) {
-      LLVM_DEBUG(dbgs() << "in block " << printMBBReference(MBB) << "\n");
-      LLVM_DEBUG(dbgs() << "  begin        state: " << Info.Pred << "\n");
-      LLVM_DEBUG(dbgs() << "  expected end state: " << Info.Exit << "\n");
-      LLVM_DEBUG(dbgs() << "  actual   end state: " << CurInfo << "\n");
-    }
-    assert(CurInfo == Info.Exit &&
-           "InsertVSETVLI dataflow invariant violated");
+  const auto &Info = BlockInfo[MBB.getNumber()];
+  if (CurInfo != Info.Exit) {
+    LLVM_DEBUG(dbgs() << "in block " << printMBBReference(MBB) << "\n");
+    LLVM_DEBUG(dbgs() << "  begin        state: " << Info.Pred << "\n");
+    LLVM_DEBUG(dbgs() << "  expected end state: " << Info.Exit << "\n");
+    LLVM_DEBUG(dbgs() << "  actual   end state: " << CurInfo << "\n");
   }
+  assert(CurInfo == Info.Exit && "InsertVSETVLI dataflow invariant violated");
 }
 
 /// Perform simple partial redundancy elimination of the VSETVLI instructions