[llvm-exegesis] Honor -mcpu in analysis mode.

This is useful to set the baseline model for an unknown CPU.

Fixes PR50013.

Differential Revision: https://reviews.llvm.org/D100743

3 files changed, 9 insertions, 5 deletions

diff --git a/llvm/tools/llvm-exegesis/lib/Analysis.cpp b/llvm/tools/llvm-exegesis/lib/Analysis.cpp
index ac21de1..a1f576d 100644
--- a/llvm/tools/llvm-exegesis/lib/Analysis.cpp
+++ b/llvm/tools/llvm-exegesis/lib/Analysis.cpp
@@ -154,7 +154,8 @@ void Analysis::printInstructionRowCsv(const size_t PointId,
 Analysis::Analysis(const Target &Target, std::unique_ptr<MCInstrInfo> InstrInfo,
                    const InstructionBenchmarkClustering &Clustering,
                    double AnalysisInconsistencyEpsilon,
-                   bool AnalysisDisplayUnstableOpcodes)
+                   bool AnalysisDisplayUnstableOpcodes,
+                   const std::string &ForceCpuName)
     : Clustering_(Clustering), InstrInfo_(std::move(InstrInfo)),
       AnalysisInconsistencyEpsilonSquared_(AnalysisInconsistencyEpsilon *
                                            AnalysisInconsistencyEpsilon),
@@ -163,12 +164,14 @@ Analysis::Analysis(const Target &Target, std::unique_ptr<MCInstrInfo> InstrInfo,
     return;
 
   const InstructionBenchmark &FirstPoint = Clustering.getPoints().front();
+  const std::string CpuName =
+      ForceCpuName.empty() ? FirstPoint.CpuName : ForceCpuName;
   RegInfo_.reset(Target.createMCRegInfo(FirstPoint.LLVMTriple));
   MCTargetOptions MCOptions;
   AsmInfo_.reset(
       Target.createMCAsmInfo(*RegInfo_, FirstPoint.LLVMTriple, MCOptions));
-  SubtargetInfo_.reset(Target.createMCSubtargetInfo(FirstPoint.LLVMTriple,
-                                                    FirstPoint.CpuName, ""));
+  SubtargetInfo_.reset(
+      Target.createMCSubtargetInfo(FirstPoint.LLVMTriple, CpuName, ""));
   InstPrinter_.reset(Target.createMCInstPrinter(
       Triple(FirstPoint.LLVMTriple), 0 /*default variant*/, *AsmInfo_,
       *InstrInfo_, *RegInfo_));
diff --git a/llvm/tools/llvm-exegesis/lib/Analysis.h b/llvm/tools/llvm-exegesis/lib/Analysis.h
index 4c1c864..0f8209c 100644
--- a/llvm/tools/llvm-exegesis/lib/Analysis.h
+++ b/llvm/tools/llvm-exegesis/lib/Analysis.h
@@ -39,7 +39,8 @@ public:
   Analysis(const Target &Target, std::unique_ptr<MCInstrInfo> InstrInfo,
            const InstructionBenchmarkClustering &Clustering,
            double AnalysisInconsistencyEpsilon,
-           bool AnalysisDisplayUnstableOpcodes);
+           bool AnalysisDisplayUnstableOpcodes,
+           const std::string &ForceCpuName = "");
 
   // Prints a csv of instructions for each cluster.
   struct PrintClusters {};
diff --git a/llvm/tools/llvm-exegesis/llvm-exegesis.cpp b/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
index 9cbcc1b..b26d3b6 100644
--- a/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
+++ b/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
@@ -436,7 +436,7 @@ static void analysisMain() {
 
   const Analysis Analyzer(*TheTarget, std::move(InstrInfo), Clustering,
                           AnalysisInconsistencyEpsilon,
-                          AnalysisDisplayUnstableOpcodes);
+                          AnalysisDisplayUnstableOpcodes, CpuName);
 
   maybeRunAnalysis<Analysis::PrintClusters>(Analyzer, "analysis clusters",
                                             AnalysisClustersOutputFile);