[llvm] [SandboxIR] Add pointer-diff utility function (PR #110176)

[via llvm-commits]

https://github.com/Sterling-Augustine created https://github.com/llvm/llvm-project/pull/110176

This will be used when gathering seeds to calculate the lane an instruction in the bundle uses.

>From cba50ef42245e2c33e85c18e61be815e2b2840c2 Mon Sep 17 00:00:00 2001
From: Sterling Augustine <saugustine at google.com>
Date: Wed, 25 Sep 2024 13:18:32 -0700
Subject: [PATCH] [SandboxIR] Add pointer-diff utility function.

This will be used when gathering seeds to calculate the lane
an instruction in the bundle uses.
---
 llvm/include/llvm/SandboxIR/Utils.h    | 33 +++++++++++
 llvm/unittests/SandboxIR/UtilsTest.cpp | 77 ++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)

diff --git a/llvm/include/llvm/SandboxIR/Utils.h b/llvm/include/llvm/SandboxIR/Utils.h
index 4e8a175f547059..9f1c08d2b6c308 100644
--- a/llvm/include/llvm/SandboxIR/Utils.h
+++ b/llvm/include/llvm/SandboxIR/Utils.h
@@ -12,8 +12,12 @@
 #ifndef LLVM_SANDBOXIR_UTILS_H
 #define LLVM_SANDBOXIR_UTILS_H
 
+#include "llvm/Analysis/LoopAccessAnalysis.h"
 #include "llvm/Analysis/MemoryLocation.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/SandboxIR/SandboxIR.h"
+#include <optional>
 
 namespace llvm::sandboxir {
 
@@ -57,6 +61,35 @@ class Utils {
   memoryLocationGetOrNone(const Instruction *I) {
     return llvm::MemoryLocation::getOrNone(cast<llvm::Instruction>(I->Val));
   }
+  /// \Returns true if \p I1 accesses a memory location lower than \p I2.
+  template <typename LoadOrStoreT>
+  static bool atLowerAddress(LoadOrStoreT *I0, LoadOrStoreT *I1,
+                             ScalarEvolution &SE, const DataLayout &DL) {
+    auto Diff = getPointerDiffInBytes(I0, I1, SE, DL);
+    if (!Diff)
+      return false;
+    return *Diff > 0;
+  }
+
+  /// \Returns the number gap between the memory locations accessed by \p I0 and
+  /// \p I1 in bytes.
+  template <typename LoadOrStoreT>
+  static std::optional<int>
+  getPointerDiffInBytes(LoadOrStoreT *I0, LoadOrStoreT *I1, ScalarEvolution &SE,
+                        const DataLayout &DL) {
+    static_assert(std::is_same<LoadOrStoreT, sandboxir::LoadInst>::value ||
+                      std::is_same<LoadOrStoreT, sandboxir::StoreInst>::value,
+                  "Expected sandboxir::Load or sandboxir::Store!");
+    llvm::Value *Opnd0 = I0->getPointerOperand()->Val;
+    llvm::Value *Opnd1 = I1->getPointerOperand()->Val;
+    llvm::Value *Ptr0 = getUnderlyingObject(Opnd0);
+    llvm::Value *Ptr1 = getUnderlyingObject(Opnd1);
+    if (Ptr0 != Ptr1)
+      return false;
+    llvm::Type *ElemTy = llvm::Type::getInt8Ty(SE.getContext());
+    return getPointersDiff(ElemTy, Opnd0, ElemTy, Opnd1, DL, SE,
+                           /*StrictCheck=*/false, /*CheckType=*/false);
+  }
 };
 } // namespace llvm::sandboxir
 
diff --git a/llvm/unittests/SandboxIR/UtilsTest.cpp b/llvm/unittests/SandboxIR/UtilsTest.cpp
index ded3edf1206a4b..7b2ce3c9b7f05e 100644
--- a/llvm/unittests/SandboxIR/UtilsTest.cpp
+++ b/llvm/unittests/SandboxIR/UtilsTest.cpp
@@ -7,9 +7,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/SandboxIR/Utils.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/AsmParser/Parser.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Module.h"
@@ -54,3 +59,75 @@ define void @foo(ptr %arg0) {
   EXPECT_EQ(sandboxir::Utils::memoryLocationGetOrNone(Ld),
             MemoryLocation::getOrNone(LLVMLd));
 }
+
+TEST_F(UtilsTest, GetPointerDiffInBytes) {
+  parseIR(C, R"IR(
+define void @foo(ptr %ptr) {
+  %gep0 = getelementptr inbounds float, ptr %ptr, i64 0
+  %gep1 = getelementptr inbounds float, ptr %ptr, i64 1
+  %gep2 = getelementptr inbounds float, ptr %ptr, i64 2
+  %gep3 = getelementptr inbounds float, ptr %ptr, i64 3
+
+  %ld0 = load float, ptr %gep0
+  %ld1 = load float, ptr %gep1
+  %ld2 = load float, ptr %gep2
+  %ld3 = load float, ptr %gep3
+
+  %v2ld0 = load <2 x float>, ptr %gep0
+  %v2ld1 = load <2 x float>, ptr %gep1
+  %v2ld2 = load <2 x float>, ptr %gep2
+  %v2ld3 = load <2 x float>, ptr %gep3
+
+  %v3ld0 = load <3 x float>, ptr %gep0
+  %v3ld1 = load <3 x float>, ptr %gep1
+  %v3ld2 = load <3 x float>, ptr %gep2
+  %v3ld3 = load <3 x float>, ptr %gep3
+  ret void
+}
+)IR");
+  llvm::Function &LLVMF = *M->getFunction("foo");
+  DominatorTree DT(LLVMF);
+  TargetLibraryInfoImpl TLII;
+  TargetLibraryInfo TLI(TLII);
+  DataLayout DL(M->getDataLayout());
+  AssumptionCache AC(LLVMF);
+  BasicAAResult BAA(DL, LLVMF, TLI, AC, &DT);
+  AAResults AA(TLI);
+  AA.addAAResult(BAA);
+  LoopInfo LI(DT);
+  ScalarEvolution SE(LLVMF, TLI, AC, DT, LI);
+  sandboxir::Context Ctx(C);
+
+  auto &F = *Ctx.createFunction(&LLVMF);
+  auto &BB = *F.begin();
+  auto It = std::next(BB.begin(), 4);
+  auto *L0 = cast<sandboxir::LoadInst>(&*It++);
+  auto *L1 = cast<sandboxir::LoadInst>(&*It++);
+  auto *L2 = cast<sandboxir::LoadInst>(&*It++);
+  auto *L3 = cast<sandboxir::LoadInst>(&*It++);
+  (void)L3;
+
+  auto *V2L0 = cast<sandboxir::LoadInst>(&*It++);
+  auto *V2L1 = cast<sandboxir::LoadInst>(&*It++);
+  auto *V2L2 = cast<sandboxir::LoadInst>(&*It++);
+  auto *V2L3 = cast<sandboxir::LoadInst>(&*It++);
+
+  auto *V3L0 = cast<sandboxir::LoadInst>(&*It++);
+  (void)V3L0;
+  auto *V3L1 = cast<sandboxir::LoadInst>(&*It++);
+  auto *V3L2 = cast<sandboxir::LoadInst>(&*It++);
+  (void)V3L2;
+  auto *V3L3 = cast<sandboxir::LoadInst>(&*It++);
+  (void)V3L3;
+
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(L0, L1, SE, DL), 4);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(L0, L2, SE, DL), 8);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(L1, L0, SE, DL), -4);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(L0, V2L0, SE, DL), 0);
+
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(L0, V2L1, SE, DL), 4);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(L0, V3L1, SE, DL), 4);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(V2L0, V2L2, SE, DL), 8);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(V2L0, V2L3, SE, DL), 12);
+  EXPECT_EQ(*sandboxir::Utils::getPointerDiffInBytes(V2L3, V2L0, SE, DL), -12);
+}