[llvm] [LoopInterchange] Constrain load/stores in a loop (PR #118973)
Madhur Amilkanthwar via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 6 06:16:47 PST 2024
https://github.com/madhur13490 updated https://github.com/llvm/llvm-project/pull/118973
>From ca6235d2844ac2202f08ad89ff1d89c2df501c48 Mon Sep 17 00:00:00 2001
From: Madhur Amilkanthwar <madhura at nvidia.com>
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 100th 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.
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 | 26 +-
.../LoopInterchange/many-load-stores.ll | 257 ++++++++++++++++++
2 files changed, 272 insertions(+), 11 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 a0c0080c0bda1c..7f5afe9790a21d 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -66,8 +66,8 @@ using CharMatrix = std::vector<std::vector<char>>;
} // end anonymous namespace
-// Maximum number of dependencies that can be handled in the dependency matrix.
-static const unsigned MaxMemInstrCount = 100;
+// Maximum number of load-stores that can be handled in the dependency matrix.
+static const unsigned MaxMemInstrCount = 64;
// Maximum loop depth supported.
static const unsigned MaxLoopNestDepth = 10;
@@ -84,7 +84,8 @@ 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<Value *, 16>;
ValueVector MemInstr;
@@ -110,6 +111,16 @@ 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())
+ << "Reached maximum loads/stores than can be supported in the loop.";
+ });
+ return false;
+ }
ValueVector::iterator I, IE, J, JE;
StringSet<> Seen;
@@ -161,12 +172,6 @@ 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 +455,7 @@ 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;
}
@@ -1728,7 +1733,6 @@ PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
// 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<CacheCost> 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 00000000000000..c57c0c7249a984
--- /dev/null
+++ b/llvm/test/Transforms/LoopInterchange/many-load-stores.ll
@@ -0,0 +1,257 @@
+; REQUIRES: asserts
+; RUN: opt < %s -passes=loop-interchange -debug -disable-output 2>&1 | FileCheck %s
+target triple = "aarch64-unknown-linux-gnu"
+
+ at A = dso_local local_unnamed_addr global [2048 x [2048 x i32]] zeroinitializer, align 4
+ at B = dso_local local_unnamed_addr global [2048 x [2048 x i32]] zeroinitializer, align 4
+ at C = dso_local local_unnamed_addr global [2048 x [2048 x i32]] zeroinitializer, align 4
+
+; CHECK: The transform doesn't support more than 64 load stores in a loop
+; CHECK: Populating dependency matrix failed
+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
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