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[BOLT] Fix double conversion in CacheMetrics (#75253)

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The change (i) fixes an issue with double-int conversion in CacheMetrics
and
(ii) removes command-line options for computing metrics (which aren't
modified
anyway).
This change might break some tests verifying the exact output of
CacheMetrics.
This commit is contained in:
spupyrev
2024-01-12 10:27:12 -08:00
committed by GitHub
parent 97a9dbb649
commit 0daf303e79
1 changed files with 15 additions and 18 deletions
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33
bolt/lib/Passes/CacheMetrics.cpp
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@@ -14,23 +14,20 @@
#include "bolt/Passes/CacheMetrics.h"
#include "bolt/Core/BinaryBasicBlock.h"
#include "bolt/Core/BinaryFunction.h"
#include "llvm/Support/CommandLine.h"
#include <unordered_map>
using namespace llvm;
using namespace bolt;
namespace opts {
extern cl::OptionCategory BoltOptCategory;
extern cl::opt<unsigned> ITLBPageSize;
extern cl::opt<unsigned> ITLBEntries;
} // namespace opts
namespace {
/// The following constants are used to estimate the number of i-TLB cache
/// misses for a given code layout. Empirically the values result in high
/// correlations between the estimations and the perf measurements.
/// The constants do not affect the code layout algorithms.
constexpr unsigned ITLBPageSize = 4096;
constexpr unsigned ITLBEntries = 16;
/// Initialize and return a position map for binary basic blocks
void extractBasicBlockInfo(
const std::vector<BinaryFunction *> &BinaryFunctions,
@@ -133,9 +130,6 @@ double expectedCacheHitRatio(
const std::vector<BinaryFunction *> &BinaryFunctions,
const std::unordered_map<BinaryBasicBlock *, uint64_t> &BBAddr,
const std::unordered_map<BinaryBasicBlock *, uint64_t> &BBSize) {
const double PageSize = opts::ITLBPageSize;
const uint64_t CacheEntries = opts::ITLBEntries;
std::unordered_map<const BinaryFunction *, Predecessors> Calls =
extractFunctionCalls(BinaryFunctions);
// Compute 'hotness' of the functions
@@ -155,7 +149,8 @@ double expectedCacheHitRatio(
for (BinaryFunction *BF : BinaryFunctions) {
if (BF->getLayout().block_empty())
continue;
double Page = BBAddr.at(BF->getLayout().block_front()) / PageSize;
const uint64_t Page =
BBAddr.at(BF->getLayout().block_front()) / ITLBPageSize;
PageSamples[Page] += FunctionSamples.at(BF);
}
@@ -166,15 +161,17 @@ double expectedCacheHitRatio(
if (BF->getLayout().block_empty() || FunctionSamples.at(BF) == 0.0)
continue;
double Samples = FunctionSamples.at(BF);
double Page = BBAddr.at(BF->getLayout().block_front()) / PageSize;
const uint64_t Page =
BBAddr.at(BF->getLayout().block_front()) / ITLBPageSize;
// The probability that the page is not present in the cache
double MissProb = pow(1.0 - PageSamples[Page] / TotalSamples, CacheEntries);
const double MissProb =
pow(1.0 - PageSamples[Page] / TotalSamples, ITLBEntries);
// Processing all callers of the function
for (std::pair<BinaryFunction *, uint64_t> Pair : Calls[BF]) {
BinaryFunction *SrcFunction = Pair.first;
double SrcPage =
BBAddr.at(SrcFunction->getLayout().block_front()) / PageSize;
const uint64_t SrcPage =
BBAddr.at(SrcFunction->getLayout().block_front()) / ITLBPageSize;
// Is this a 'long' or a 'short' call?
if (Page != SrcPage) {
// This is a miss