[llvm-exegesis] Restrict to allowed back-to-back instructions in SerialSnippetGenerator.

Summary: Followup to D73161.

Reviewers: gchatelet, mstojanovic

Subscribers: tschuett, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73256

Author: legrosbuffle

llvm/tools/llvm-exegesis/lib/SerialSnippetGenerator.cpp

@@ -8,8 +8,9 @@
 
 #include "SerialSnippetGenerator.h"
 
-#include "MCInstrDescView.h"
 #include "CodeTemplate.h"
+#include "MCInstrDescView.h"
+#include "Target.h"
 #include <algorithm>
 #include <numeric>
 #include <vector>
@@ -50,6 +51,8 @@ computeAliasingInstructions(const LLVMState &State, const Instruction *Instr,
     const Instruction &OtherInstr = State.getIC().getInstr(OtherOpcode);
     if (OtherInstr.hasMemoryOperands())
       continue;
+    if (!State.getExegesisTarget().allowAsBackToBack(OtherInstr))
+      continue;
     if (Instr->hasAliasingRegistersThrough(OtherInstr, ForbiddenRegisters))
       AliasingInstructions.push_back(&OtherInstr);
     if (AliasingInstructions.size() >= MaxAliasingInstructions)