From 5605a1eeddeb87abdf39a60bc59303c5dc978154 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@google.com>
Date: Fri, 15 Jul 2022 23:58:11 -0700
Subject: [PATCH] Use drop_begin (NFC)

---
 llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp     |  4 ++--
 mlir/lib/Target/Cpp/TranslateToCpp.cpp               |  3 +--
 mlir/lib/Target/LLVMIR/ModuleTranslation.cpp         | 16 +++++++---------
 mlir/lib/Target/SPIRV/Serialization/SerializeOps.cpp |  2 +-
 4 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index 975eb88..05f3143 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -1213,8 +1213,8 @@ void SystemZXPLINKFrameLowering::emitPrologue(MachineFunction &MF,
     // Mark the FramePtr as live at the beginning of every block except
     // the entry block.  (We'll have marked R8 as live on entry when
     // saving the GPRs.)
-    for (auto I = std::next(MF.begin()), E = MF.end(); I != E; ++I)
-      I->addLiveIn(Regs.getFramePointerRegister());
+    for (MachineBasicBlock &B : llvm::drop_begin(MF))
+      B.addLiveIn(Regs.getFramePointerRegister());
   }
 }
 
diff --git a/mlir/lib/Target/Cpp/TranslateToCpp.cpp b/mlir/lib/Target/Cpp/TranslateToCpp.cpp
index b3878eb..3b3fba1 100644
--- a/mlir/lib/Target/Cpp/TranslateToCpp.cpp
+++ b/mlir/lib/Target/Cpp/TranslateToCpp.cpp
@@ -645,8 +645,7 @@ static LogicalResult printOperation(CppEmitter &emitter,
   }
 
   // Declare variables for basic block arguments.
-  for (auto it = std::next(blocks.begin()); it != blocks.end(); ++it) {
-    Block &block = *it;
+  for (Block &block : llvm::drop_begin(blocks)) {
     for (BlockArgument &arg : block.getArguments()) {
       if (emitter.hasValueInScope(arg))
         return functionOp.emitOpError(" block argument #")
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index 182274e..4855571 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -485,17 +485,15 @@ void mlir::LLVM::detail::connectPHINodes(Region &region,
                                          const ModuleTranslation &state) {
   // Skip the first block, it cannot be branched to and its arguments correspond
   // to the arguments of the LLVM function.
-  for (auto it = std::next(region.begin()), eit = region.end(); it != eit;
-       ++it) {
-    Block *bb = &*it;
-    llvm::BasicBlock *llvmBB = state.lookupBlock(bb);
+  for (Block &bb : llvm::drop_begin(region)) {
+    llvm::BasicBlock *llvmBB = state.lookupBlock(&bb);
     auto phis = llvmBB->phis();
-    auto numArguments = bb->getNumArguments();
+    auto numArguments = bb.getNumArguments();
     assert(numArguments == std::distance(phis.begin(), phis.end()));
     for (auto &numberedPhiNode : llvm::enumerate(phis)) {
       auto &phiNode = numberedPhiNode.value();
       unsigned index = numberedPhiNode.index();
-      for (auto *pred : bb->getPredecessors()) {
+      for (auto *pred : bb.getPredecessors()) {
         // Find the LLVM IR block that contains the converted terminator
         // instruction and use it in the PHI node. Note that this block is not
         // necessarily the same as state.lookupBlock(pred), some operations
@@ -504,9 +502,9 @@ void mlir::LLVM::detail::connectPHINodes(Region &region,
         llvm::Instruction *terminator =
             state.lookupBranch(pred->getTerminator());
         assert(terminator && "missing the mapping for a terminator");
-        phiNode.addIncoming(
-            state.lookupValue(getPHISourceValue(bb, pred, numArguments, index)),
-            terminator->getParent());
+        phiNode.addIncoming(state.lookupValue(getPHISourceValue(
+                                &bb, pred, numArguments, index)),
+                            terminator->getParent());
       }
     }
   }
diff --git a/mlir/lib/Target/SPIRV/Serialization/SerializeOps.cpp b/mlir/lib/Target/SPIRV/Serialization/SerializeOps.cpp
index cdf7fc5..ad1724f 100644
--- a/mlir/lib/Target/SPIRV/Serialization/SerializeOps.cpp
+++ b/mlir/lib/Target/SPIRV/Serialization/SerializeOps.cpp
@@ -420,7 +420,7 @@ LogicalResult Serializer::processLoopOp(spirv::LoopOp loopOp) {
   // properly. We don't need to assign for the entry block, which is just for
   // satisfying MLIR region's structural requirement.
   auto &body = loopOp.body();
-  for (Block &block : llvm::make_range(std::next(body.begin(), 1), body.end()))
+  for (Block &block : llvm::drop_begin(body))
     getOrCreateBlockID(&block);
 
   auto *headerBlock = loopOp.getHeaderBlock();
-- 
2.7.4