[clang] [llvm] [AVR] Fix Avr indvar detection and strength reduction (missed optimization) (PR #152028)

[Ben Shi via llvm-commits]

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@@ -0,0 +1,68 @@
+//===- AVRTargetTransformInfo.h - AVR specific TTI ---------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This file defines a TargetTransformInfoImplBase conforming object specific
+/// to the AVR target machine. It uses the target's detailed information to
+/// provide more precise answers to certain TTI queries, while letting the
+/// target independent and default TTI implementations handle the rest.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_AVR_AVRTARGETTRANSFORMINFO_H
+#define LLVM_LIB_TARGET_AVR_AVRTARGETTRANSFORMINFO_H
+
+#include "AVRSubtarget.h"
+#include "AVRTargetMachine.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/CodeGen/BasicTTIImpl.h"
+#include "llvm/IR/Function.h"
+#include <optional>
+
+namespace llvm {
+
+class AVRTTIImpl final : public BasicTTIImplBase<AVRTTIImpl> {
+  using BaseT = BasicTTIImplBase<AVRTTIImpl>;
+  using TTI = TargetTransformInfo;
+
+  friend BaseT;
+
+  const AVRSubtarget *ST;
+  const AVRTargetLowering *TLI;
+  const Function *currentF;
+
+  const AVRSubtarget *getST() const { return ST; }
+  const AVRTargetLowering *getTLI() const { return TLI; }
+
+public:
+  explicit AVRTTIImpl(const AVRTargetMachine *TM, const Function &F)
+      : BaseT(TM, F.getDataLayout()), ST(TM->getSubtargetImpl(F)),
+        TLI(ST->getTargetLowering()), currentF(&F) {}
+
+  bool isLSRCostLess(const TargetTransformInfo::LSRCost &C1,
+                     const TargetTransformInfo::LSRCost &C2) const override {
+    // Detect %incdec.ptr because loop-reduce loses them
+    for (const BasicBlock &BB : *currentF) {
+      if (BB.getName().find("while.body") != std::string::npos) {
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benshi001 wrote:

We should not rely on names to find loop body, what if other compilers like flang-frontend and rustc do not use these names?

https://github.com/llvm/llvm-project/pull/152028