From 2e3567d449262b1360088ce38557175dfdbb72a5 Mon Sep 17 00:00:00 2001 From: Madhur Amilkanthwar Date: Thu, 5 Dec 2024 21:08:48 -0800 Subject: [PATCH] [LoopInterchange] Constrain load/stores in a loop In the current state of the code, the transform computes entries for the dependency matrix until MaxMemInstrCount which is 100. After 99th entry it terminates and thus overall wastes compile-time. It would be nice if we can compute total number of entries upfront and early exit if the number of entries > 100. However, computing the number of entries is not always possible as it depends on two factors: 1. Number of load-store pairs in a loop. 2. Number of common loop levels for each of the pair. This patch just constrains the whole computation on the number of loads and store instructions in the loop. With 64, I see 39 interchanges compared to 42 with the trunk. (With 128, it is 42 vs 43 but I see increase in the compile-time.) In an other approach, I experimented with computing 1 and constraining the number of pairs but that did not lead to any additional benefit in terms of compile-time. However, when other issues are fixed, I can revisit this approach. --- .../lib/Transforms/Scalar/LoopInterchange.cpp | 42 ++- .../LoopInterchange/many-load-stores.ll | 260 ++++++++++++++++++ 2 files changed, 289 insertions(+), 13 deletions(-) create mode 100644 llvm/test/Transforms/LoopInterchange/many-load-stores.ll diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp index a0c0080c0bda1..e64e052dece17 100644 --- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp +++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp @@ -57,6 +57,14 @@ static cl::opt LoopInterchangeCostThreshold( "loop-interchange-threshold", cl::init(0), cl::Hidden, cl::desc("Interchange if you gain more than this number")); +// Maximum number of load-stores that can be handled in the dependency matrix. +static cl::opt MaxMemInstrCount( + "loop-interchange-max-meminstr-count", cl::init(64), cl::Hidden, + cl::desc( + "Maximum number of load-store instructions that should be handled " + "in the dependency matrix. Higher value may lead to more interchanges " + "at the cost of compile-time")); + namespace { using LoopVector = SmallVector; @@ -66,9 +74,6 @@ using CharMatrix = std::vector>; } // end anonymous namespace -// Maximum number of dependencies that can be handled in the dependency matrix. -static const unsigned MaxMemInstrCount = 100; - // Maximum loop depth supported. static const unsigned MaxLoopNestDepth = 10; @@ -84,7 +89,8 @@ static void printDepMatrix(CharMatrix &DepMatrix) { static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level, Loop *L, DependenceInfo *DI, - ScalarEvolution *SE) { + ScalarEvolution *SE, + OptimizationRemarkEmitter *ORE) { using ValueVector = SmallVector; ValueVector MemInstr; @@ -109,7 +115,18 @@ static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level, LLVM_DEBUG(dbgs() << "Found " << MemInstr.size() << " Loads and Stores to analyze\n"); - + if (MemInstr.size() > MaxMemInstrCount) { + LLVM_DEBUG(dbgs() << "The transform doesn't support more than " + << MaxMemInstrCount << " load/stores in a loop\n"); + ORE->emit([&]() { + return OptimizationRemarkMissed(DEBUG_TYPE, "UnsupportedLoop", + L->getStartLoc(), L->getHeader()) + << "Number of loads/stores exceeded, the supported maximum " + "can be increased with option " + "-loop-interchange-maxmeminstr-count."; + }); + return false; + } ValueVector::iterator I, IE, J, JE; StringSet<> Seen; @@ -161,12 +178,6 @@ static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level, // Make sure we only add unique entries to the dependency matrix. if (Seen.insert(StringRef(Dep.data(), Dep.size())).second) DepMatrix.push_back(Dep); - - if (DepMatrix.size() > MaxMemInstrCount) { - LLVM_DEBUG(dbgs() << "Cannot handle more than " << MaxMemInstrCount - << " dependencies inside loop\n"); - return false; - } } } } @@ -450,7 +461,7 @@ struct LoopInterchange { CharMatrix DependencyMatrix; Loop *OuterMostLoop = *(LoopList.begin()); if (!populateDependencyMatrix(DependencyMatrix, LoopNestDepth, - OuterMostLoop, DI, SE)) { + OuterMostLoop, DI, SE, ORE)) { LLVM_DEBUG(dbgs() << "Populating dependency matrix failed\n"); return false; } @@ -1725,10 +1736,15 @@ PreservedAnalyses LoopInterchangePass::run(LoopNest &LN, LPMUpdater &U) { Function &F = *LN.getParent(); SmallVector LoopList(LN.getLoops()); + + if (MaxMemInstrCount < 1) { + LLVM_DEBUG(dbgs() << "MaxMemInstrCount should be at least 1"); + return PreservedAnalyses::all(); + } + // Ensure minimum depth of the loop nest to do the interchange. if (!hasMinimumLoopDepth(LoopList)) return PreservedAnalyses::all(); - DependenceInfo DI(&F, &AR.AA, &AR.SE, &AR.LI); std::unique_ptr CC = CacheCost::getCacheCost(LN.getOutermostLoop(), AR, DI); diff --git a/llvm/test/Transforms/LoopInterchange/many-load-stores.ll b/llvm/test/Transforms/LoopInterchange/many-load-stores.ll new file mode 100644 index 0000000000000..2eb999361988c --- /dev/null +++ b/llvm/test/Transforms/LoopInterchange/many-load-stores.ll @@ -0,0 +1,260 @@ +; RUN: opt < %s -passes=loop-interchange --pass-remarks-missed=loop-interchange -disable-output 2>&1 | FileCheck %s +; RUN: opt < %s -passes=loop-interchange --pass-remarks-missed=loop-interchange -loop-interchange-max-meminstr-count=75 +; -disable-output 2>&1 | FileCheck --check-prefix=CHECK-INSTR-COUNT %s +target triple = "aarch64-unknown-linux-gnu" + +@A = dso_local local_unnamed_addr global [2048 x [2048 x i32]] zeroinitializer, align 4 +@B = dso_local local_unnamed_addr global [2048 x [2048 x i32]] zeroinitializer, align 4 +@C = dso_local local_unnamed_addr global [2048 x [2048 x i32]] zeroinitializer, align 4 + +; CHECK: Number of loads/stores exceeded, the supported maximum +; can be increased with option -loop-interchange-maxmeminstr-count. +; CHECK-INSTR-COUNT-NOT: Number of loads/stores exceeded, the supported maximum +; can be increased with option -loop-interchange-maxmeminstr-count. +define dso_local noundef i32 @many_load_stores() { + br label %1 + +1: ; preds = %9, %0 + %2 = phi i32 [ 0, %0 ], [ %10, %9 ] + %3 = icmp slt i32 %2, 2048 + br i1 %3, label %5, label %4 + +4: ; preds = %1 + ret i32 0 + +5: ; preds = %1 + br label %6 + +6: ; preds = %11, %5 + %7 = phi i32 [ 0, %5 ], [ %208, %11 ] + %8 = icmp slt i32 %7, 85 + br i1 %8, label %11, label %9 + +9: ; preds = %6 + %10 = add nsw i32 %2, 1 + br label %1 + +11: ; preds = %6 + %12 = sext i32 %2 to i64 + %13 = getelementptr inbounds [2048 x [2048 x i32]], [2048 x [2048 x i32]]* @B, i64 0, i64 %12 + %14 = sext i32 %7 to i64 + %15 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %14 + %16 = load i32, i32* %15, align 4 + %17 = getelementptr inbounds [2048 x [2048 x i32]], [2048 x [2048 x i32]]* @C, i64 0, i64 %12 + %18 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %14 + %19 = load i32, i32* %18, align 4 + %20 = add nsw i32 %16, %19 + %21 = getelementptr inbounds [2048 x [2048 x i32]], [2048 x [2048 x i32]]* @A, i64 0, i64 %12 + %22 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %14 + store i32 %20, i32* %22, align 4 + %23 = add nsw i32 %7, 1 + %24 = sext i32 %23 to i64 + %25 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %24 + %26 = load i32, i32* %25, align 4 + %27 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %24 + %28 = load i32, i32* %27, align 4 + %29 = add nsw i32 %26, %28 + %30 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %24 + store i32 %29, i32* %30, align 4 + %31 = add nsw i32 %23, 1 + %32 = sext i32 %31 to i64 + %33 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %32 + %34 = load i32, i32* %33, align 4 + %35 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %32 + %36 = load i32, i32* %35, align 4 + %37 = add nsw i32 %34, %36 + %38 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %32 + store i32 %37, i32* %38, align 4 + %39 = add nsw i32 %31, 1 + %40 = sext i32 %39 to i64 + %41 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %40 + %42 = load i32, i32* %41, align 4 + %43 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %40 + %44 = load i32, i32* %43, align 4 + %45 = add nsw i32 %42, %44 + %46 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %40 + store i32 %45, i32* %46, align 4 + %47 = add nsw i32 %39, 1 + %48 = sext i32 %47 to i64 + %49 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %48 + %50 = load i32, i32* %49, align 4 + %51 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %48 + %52 = load i32, i32* %51, align 4 + %53 = add nsw i32 %50, %52 + %54 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %48 + store i32 %53, i32* %54, align 4 + %55 = add nsw i32 %47, 1 + %56 = sext i32 %55 to i64 + %57 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %56 + %58 = load i32, i32* %57, align 4 + %59 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %56 + %60 = load i32, i32* %59, align 4 + %61 = add nsw i32 %58, %60 + %62 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %56 + store i32 %61, i32* %62, align 4 + %63 = add nsw i32 %55, 1 + %64 = sext i32 %63 to i64 + %65 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %64 + %66 = load i32, i32* %65, align 4 + %67 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %64 + %68 = load i32, i32* %67, align 4 + %69 = add nsw i32 %66, %68 + %70 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %64 + store i32 %69, i32* %70, align 4 + %71 = add nsw i32 %63, 1 + %72 = sext i32 %71 to i64 + %73 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %72 + %74 = load i32, i32* %73, align 4 + %75 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %72 + %76 = load i32, i32* %75, align 4 + %77 = add nsw i32 %74, %76 + %78 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %72 + store i32 %77, i32* %78, align 4 + %79 = add nsw i32 %71, 1 + %80 = sext i32 %79 to i64 + %81 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %80 + %82 = load i32, i32* %81, align 4 + %83 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %80 + %84 = load i32, i32* %83, align 4 + %85 = add nsw i32 %82, %84 + %86 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %80 + store i32 %85, i32* %86, align 4 + %87 = add nsw i32 %79, 1 + %88 = sext i32 %87 to i64 + %89 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %88 + %90 = load i32, i32* %89, align 4 + %91 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %88 + %92 = load i32, i32* %91, align 4 + %93 = add nsw i32 %90, %92 + %94 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %88 + store i32 %93, i32* %94, align 4 + %95 = add nsw i32 %87, 1 + %96 = sext i32 %95 to i64 + %97 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %96 + %98 = load i32, i32* %97, align 4 + %99 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %96 + %100 = load i32, i32* %99, align 4 + %101 = add nsw i32 %98, %100 + %102 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %96 + store i32 %101, i32* %102, align 4 + %103 = add nsw i32 %95, 1 + %104 = sext i32 %103 to i64 + %105 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %104 + %106 = load i32, i32* %105, align 4 + %107 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %104 + %108 = load i32, i32* %107, align 4 + %109 = add nsw i32 %106, %108 + %110 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %104 + store i32 %109, i32* %110, align 4 + %111 = add nsw i32 %103, 1 + %112 = sext i32 %111 to i64 + %113 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %112 + %114 = load i32, i32* %113, align 4 + %115 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %112 + %116 = load i32, i32* %115, align 4 + %117 = add nsw i32 %114, %116 + %118 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %112 + store i32 %117, i32* %118, align 4 + %119 = add nsw i32 %111, 1 + %120 = sext i32 %119 to i64 + %121 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %120 + %122 = load i32, i32* %121, align 4 + %123 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %120 + %124 = load i32, i32* %123, align 4 + %125 = add nsw i32 %122, %124 + %126 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %120 + store i32 %125, i32* %126, align 4 + %127 = add nsw i32 %119, 1 + %128 = sext i32 %127 to i64 + %129 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %128 + %130 = load i32, i32* %129, align 4 + %131 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %128 + %132 = load i32, i32* %131, align 4 + %133 = add nsw i32 %130, %132 + %134 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %128 + store i32 %133, i32* %134, align 4 + %135 = add nsw i32 %127, 1 + %136 = sext i32 %135 to i64 + %137 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %136 + %138 = load i32, i32* %137, align 4 + %139 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %136 + %140 = load i32, i32* %139, align 4 + %141 = add nsw i32 %138, %140 + %142 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %136 + store i32 %141, i32* %142, align 4 + %143 = add nsw i32 %135, 1 + %144 = sext i32 %143 to i64 + %145 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %144 + %146 = load i32, i32* %145, align 4 + %147 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %144 + %148 = load i32, i32* %147, align 4 + %149 = add nsw i32 %146, %148 + %150 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %144 + store i32 %149, i32* %150, align 4 + %151 = add nsw i32 %143, 1 + %152 = sext i32 %151 to i64 + %153 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %152 + %154 = load i32, i32* %153, align 4 + %155 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %152 + %156 = load i32, i32* %155, align 4 + %157 = add nsw i32 %154, %156 + %158 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %152 + store i32 %157, i32* %158, align 4 + %159 = add nsw i32 %151, 1 + %160 = sext i32 %159 to i64 + %161 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %160 + %162 = load i32, i32* %161, align 4 + %163 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %160 + %164 = load i32, i32* %163, align 4 + %165 = add nsw i32 %162, %164 + %166 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %160 + store i32 %165, i32* %166, align 4 + %167 = add nsw i32 %159, 1 + %168 = sext i32 %167 to i64 + %169 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %168 + %170 = load i32, i32* %169, align 4 + %171 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %168 + %172 = load i32, i32* %171, align 4 + %173 = add nsw i32 %170, %172 + %174 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %168 + store i32 %173, i32* %174, align 4 + %175 = add nsw i32 %167, 1 + %176 = sext i32 %175 to i64 + %177 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %176 + %178 = load i32, i32* %177, align 4 + %179 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %176 + %180 = load i32, i32* %179, align 4 + %181 = add nsw i32 %178, %180 + %182 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %176 + store i32 %181, i32* %182, align 4 + %183 = add nsw i32 %175, 1 + %184 = sext i32 %183 to i64 + %185 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %184 + %186 = load i32, i32* %185, align 4 + %187 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %184 + %188 = load i32, i32* %187, align 4 + %189 = add nsw i32 %186, %188 + %190 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %184 + store i32 %189, i32* %190, align 4 + %191 = add nsw i32 %183, 1 + %192 = sext i32 %191 to i64 + %193 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %192 + %194 = load i32, i32* %193, align 4 + %195 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %192 + %196 = load i32, i32* %195, align 4 + %197 = add nsw i32 %194, %196 + %198 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %192 + store i32 %197, i32* %198, align 4 + %199 = add nsw i32 %191, 1 + %200 = sext i32 %199 to i64 + %201 = getelementptr inbounds [2048 x i32], [2048 x i32]* %13, i64 0, i64 %200 + %202 = load i32, i32* %201, align 4 + %203 = getelementptr inbounds [2048 x i32], [2048 x i32]* %17, i64 0, i64 %200 + %204 = load i32, i32* %203, align 4 + %205 = add nsw i32 %202, %204 + %206 = getelementptr inbounds [2048 x i32], [2048 x i32]* %21, i64 0, i64 %200 + store i32 %205, i32* %206, align 4 + %207 = add nsw i32 %199, 1 + %208 = add nsw i32 %207, 24 + br label %6 +} \ No newline at end of file