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

[Luke Lau via llvm-commits]

https://github.com/lukel97 created https://github.com/llvm/llvm-project/pull/90171

This flag has been enabled by default for almost two years now since 1f06398e96d4508d22f42b760f70eb5d4e7b1dc9, 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 unitialized VSETVLIInfo.


>From 2a3263d766de46f8642fedd9a791ed89ed7adcff Mon Sep 17 00:00:00 2001
From: Luke Lau <luke at igalia.com>
Date: Fri, 26 Apr 2024 14:07:06 +0800
Subject: [PATCH] [RISCV] Remove -riscv-insert-vsetvl-strict-asserts flag

This flag has been enabled by default for almost two years now since 1f06398e96d4508d22f42b760f70eb5d4e7b1dc9, 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 unitialized VSETVLIInfo.
---
 llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp | 37 +++++---------------
 1 file changed, 8 insertions(+), 29 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
index c40b9031543fe2..90fa0920c49283 100644
--- a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ b/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) {
@@ -1430,32 +1426,15 @@ 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