[llvm-mca] Add -skip-unsupported-instructions option

llvm/lib/MCA/InstrBuilder.cpp

@@ -542,8 +542,7 @@ InstrBuilder::createInstrDescImpl(const MCInst &MCI,
   const MCSchedClassDesc &SCDesc = *SM.getSchedClassDesc(SchedClassID);
   if (SCDesc.NumMicroOps == MCSchedClassDesc::InvalidNumMicroOps) {
     return make_error<InstructionError<MCInst>>(
-        "found an unsupported instruction in the input assembly sequence.",
-        MCI);
+        "found an unsupported instruction in the input assembly sequence", MCI);
   }
 
   LLVM_DEBUG(dbgs() << "\n\t\tOpcode Name= " << MCII.getName(Opcode) << '\n');

llvm/test/tools/llvm-mca/X86/BtVer2/skip-unsupported-instructions-none-remain.s

@@ -0,0 +1,14 @@
+# RUN: not llvm-mca -mtriple=x86_64-unknown-unknown -mcpu=btver2 -skip-unsupported-instructions %s |& FileCheck --check-prefixes=CHECK-ALL,CHECK-SKIP %s
+# RUN: not llvm-mca -mtriple=x86_64-unknown-unknown -mcpu=btver2 %s |& FileCheck --check-prefixes=CHECK-ALL,CHECK-ERROR %s
+
+# Test defends that if all instructions are skipped leaving an empty input, an error is printed.
+
+bzhi %eax, %ebx, %ecx
+
+# CHECK-ALL-NOT: error
+
+# CHECK-ERROR: error: found an unsupported instruction in the input assembly sequence, use -skip-unsupported-instructions to ignore.
+
+# CHECK-SKIP: warning: found an unsupported instruction in the input assembly sequence, skipping with -skip-unsupported-instructions, note accuracy will be impacted:
+# CHECK-SKIP: note: instruction:      bzhil   %eax, %ebx, %ecx
+# CHECK-SKIP: error: no assembly instructions found.

llvm/test/tools/llvm-mca/X86/BtVer2/unsupported-instruction.s

@@ -1,6 +1,55 @@
-# RUN: not llvm-mca -mtriple=x86_64-unknown-unknown -mcpu=btver2 %s 2>&1 | FileCheck %s
+# RUN: llvm-mca -mtriple=x86_64-unknown-unknown -mcpu=btver2 -skip-unsupported-instructions -timeline %s |& FileCheck --check-prefix=CHECK-SKIP %s
+# RUN: not llvm-mca -mtriple=x86_64-unknown-unknown -mcpu=btver2 %s |& FileCheck --check-prefix=CHECK-ERROR %s
+
+# Test checks that unsupported instructions exit with an error, unless -skip-unsupported-instructions is passed, in which case the remaining instructions should be analysed.
+
+# CHECK-SKIP: warning: found an unsupported instruction in the input assembly sequence, skipping with -skip-unsupported-instructions, note accuracy will be impacted:
+# CHECK-ERROR: error: found an unsupported instruction in the input assembly sequence, use -skip-unsupported-instructions to ignore.
 
 bzhi %eax, %ebx, %ecx
 
-# CHECK: error: found an unsupported instruction in the input assembly sequence.
-# CHECK-NEXT: note: instruction: 	bzhil	%eax, %ebx, %ecx
+# Supported instruction that may be analysed.
+add %eax, %eax
+
+# CHECK-SKIP: Iterations:        100
+# CHECK-SKIP: Instructions:      100
+# CHECK-SKIP: Total Cycles:      103
+# CHECK-SKIP: Total uOps:        100
+
+# CHECK-SKIP: Dispatch Width:    2
+# CHECK-SKIP: uOps Per Cycle:    0.97
+# CHECK-SKIP: IPC:               0.97
+# CHECK-SKIP: Block RThroughput: 0.5
+
+# CHECK-SKIP: Instruction Info:
+# CHECK-SKIP: [1]: #uOps
+# CHECK-SKIP: [2]: Latency
+# CHECK-SKIP: [3]: RThroughput
+# CHECK-SKIP: [4]: MayLoad
+# CHECK-SKIP: [5]: MayStore
+# CHECK-SKIP: [6]: HasSideEffects (U)
+
+# CHECK-SKIP: [1]    [2]    [3]    [4]    [5]    [6]    Instructions:
+# CHECK-SKIP:  1      1     0.50                        addl  %eax, %eax
+
+# CHECK-SKIP: Timeline view:
+
+# CHECK-SKIP: [0,0]     DeER .    . .   addl  %eax, %eax
+# CHECK-SKIP: [1,0]     D=eER.    . .   addl  %eax, %eax
+# CHECK-SKIP: [2,0]     .D=eER    . .   addl  %eax, %eax
+# CHECK-SKIP: [3,0]     .D==eER   . .   addl  %eax, %eax
+# CHECK-SKIP: [4,0]     . D==eER  . .   addl  %eax, %eax
+# CHECK-SKIP: [5,0]     . D===eER . .   addl  %eax, %eax
+# CHECK-SKIP: [6,0]     .  D===eER. .   addl  %eax, %eax
+# CHECK-SKIP: [7,0]     .  D====eER .   addl  %eax, %eax
+# CHECK-SKIP: [8,0]     .   D====eER.   addl  %eax, %eax
+# CHECK-SKIP: [9,0]     .   D=====eER   addl  %eax, %eax
+
+# CHECK-SKIP: Average Wait times (based on the timeline view):
+# CHECK-SKIP: [0]: Executions
+# CHECK-SKIP: [1]: Average time spent waiting in a scheduler's queue
+# CHECK-SKIP: [2]: Average time spent waiting in a scheduler's queue while ready
+# CHECK-SKIP: [3]: Average time elapsed from WB until retire stage
+
+# CHECK-SKIP:       [0]    [1]    [2]    [3]
+# CHECK-SKIP: 0.     10    3.5    0.1    0.0       addl       %eax, %eax

llvm/tools/llvm-mca/CodeRegion.h

@@ -59,6 +59,7 @@
 #define LLVM_TOOLS_LLVM_MCA_CODEREGION_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
@@ -97,6 +98,20 @@ class CodeRegion {
     Instructions.emplace_back(Instruction);
   }
 
+  // Remove the given instructions from the set, for unsupported instructions
+  // being skipped. Returns an ArrayRef for the updated vector of Instructions.
+  [[nodiscard]] llvm::ArrayRef<llvm::MCInst>
+  dropInstructions(const llvm::SmallPtrSetImpl<const llvm::MCInst *> &Insts) {
+    if (Insts.empty())
+      return Instructions;
+    Instructions.erase(std::remove_if(Instructions.begin(), Instructions.end(),
+                                      [&Insts](const llvm::MCInst &Inst) {
+                                        return Insts.contains(&Inst);
+                                      }),
+                       Instructions.end());
+    return Instructions;
+  }
+
   llvm::SMLoc startLoc() const { return RangeStart; }
   llvm::SMLoc endLoc() const { return RangeEnd; }
 

llvm/tools/llvm-mca/llvm-mca.cpp

@@ -237,6 +237,11 @@ static cl::opt<bool> DisableInstrumentManager(
              "ignores instruments.)."),
     cl::cat(ViewOptions), cl::init(false));
 
+static cl::opt<bool> SkipUnsupportedInstructions(
+    "skip-unsupported-instructions",
+    cl::desc("Make unsupported instruction errors into warnings."),
+    cl::cat(ViewOptions), cl::init(false));
+
 namespace {
 
 const Target *getTarget(const char *ProgName) {
@@ -558,6 +563,7 @@ int main(int argc, char **argv) {
   assert(MAB && "Unable to create asm backend!");
 
   json::Object JSONOutput;
+  int NonEmptyRegions = 0;
   for (const std::unique_ptr<mca::AnalysisRegion> &Region : Regions) {
     // Skip empty code regions.
     if (Region->empty())
@@ -571,14 +577,13 @@ int main(int argc, char **argv) {
 
     IPP->resetState();
 
-    DenseMap<const MCInst *, SmallVector<mca::Instrument *>>
-        InstToInstruments;
+    DenseMap<const MCInst *, SmallVector<mca::Instrument *>> InstToInstruments;
     SmallVector<std::unique_ptr<mca::Instruction>> LoweredSequence;
+    SmallPtrSet<const MCInst *, 16> DroppedInsts;
     for (const MCInst &MCI : Insts) {
       SMLoc Loc = MCI.getLoc();
       const SmallVector<mca::Instrument *> Instruments =
           InstrumentRegions.getActiveInstruments(Loc);
-      InstToInstruments.insert({&MCI, Instruments});
 
       Expected<std::unique_ptr<mca::Instruction>> Inst =
           IB.createInstruction(MCI, Instruments);
@@ -588,7 +593,15 @@ int main(int argc, char **argv) {
                 [&IP, &STI](const mca::InstructionError<MCInst> &IE) {
                   std::string InstructionStr;
                   raw_string_ostream SS(InstructionStr);
-                  WithColor::error() << IE.Message << '\n';
+                  if (SkipUnsupportedInstructions)
+                    WithColor::warning()
+                        << IE.Message
+                        << ", skipping with -skip-unsupported-instructions, "
+                           "note accuracy will be impacted:\n";
+                  else
+                    WithColor::error()
+                        << IE.Message
+                        << ", use -skip-unsupported-instructions to ignore.\n";
                   IP->printInst(&IE.Inst, 0, "", *STI, SS);
                   SS.flush();
                   WithColor::note()
@@ -597,14 +610,25 @@ int main(int argc, char **argv) {
           // Default case.
           WithColor::error() << toString(std::move(NewE));
         }
+        if (SkipUnsupportedInstructions) {
+          DroppedInsts.insert(&MCI);
+          continue;
+        }
         return 1;
       }
 
       IPP->postProcessInstruction(Inst.get(), MCI);
-
+      InstToInstruments.insert({&MCI, Instruments});
       LoweredSequence.emplace_back(std::move(Inst.get()));
     }
 
+    Insts = Region->dropInstructions(DroppedInsts);
+
+    // Skip empty regions.
+    if (Insts.empty())
+      continue;
+    NonEmptyRegions++;
+
     mca::CircularSourceMgr S(LoweredSequence,
                              PrintInstructionTables ? 1 : Iterations);
 
@@ -759,6 +783,11 @@ int main(int argc, char **argv) {
     ++RegionIdx;
   }
 
+  if (NonEmptyRegions == 0) {
+    WithColor::error() << "no assembly instructions found.\n";
+    return 1;
+  }
+
   if (PrintJson)
     TOF->os() << formatv("{0:2}", json::Value(std::move(JSONOutput))) << "\n";