[RISCV][llvm-mca] Use LMUL Instruments to provide more accurate reports on RISCV

On x86 and AArch, SIMD instructions encode all of the scheduling information in the instruction
itself. For example, VADD.I16 q0, q1, q2 is a neon instruction that operates on 16-bit integer
elements stored in 128-bit Q registers, which leads to eight 16-bit lanes in parallel. This kind
of information impacts how the instruction takes to execute and what dependencies this may cause.

On RISCV however, the data that impacts scheduling is encoded in CSR registers such as vtype or
vl, in addition with the instruction itself. But MCA does not track or use the data in these
registers. This patch fixes this problem by introducing Instruments into MCA.

* Replace `CodeRegions` with `AnalysisRegions`
* Add `Instrument` and `InstrumentManager`
* Add `InstrumentRegions`
* Add RISCV Instrument and `InstrumentManager`
* Parse `Instruments` in driver
* Use instruments to override schedule class
* RISCV use lmul instrument to override schedule class
* Fix unit tests to pass empty instruments
* Add -ignore-im clopt to disable this change

A prior version of this patch was commited in. It was reverted in
5e82ee5373211db8522181054800ccd49461d9d8. 2323a4ee610f5e1db74d362af4c6fb8c704be8f6 reverted
that change because the unit test files caused build errors. This commit adds the original changes
and the fixed test files.

Differential Revision: https://reviews.llvm.org/D137440

1 files changed, 52 insertions, 8 deletions

diff --git a/llvm/tools/llvm-mca/llvm-mca.cpp b/llvm/tools/llvm-mca/llvm-mca.cpp
index 6f7b74f..2a27fea 100644
--- a/llvm/tools/llvm-mca/llvm-mca.cpp
+++ b/llvm/tools/llvm-mca/llvm-mca.cpp
@@ -231,6 +231,12 @@ static cl::opt<bool> DisableCustomBehaviour(
         "Disable custom behaviour (use the default class which does nothing)."),
     cl::cat(ViewOptions), cl::init(false));
 
+static cl::opt<bool> DisableInstrumentManager(
+    "disable-im",
+    cl::desc("Disable instrumentation manager (use the default class which "
+             "ignores instruments.)."),
+    cl::cat(ViewOptions), cl::init(false));
+
 namespace {
 
 const Target *getTarget(const char *ProgName) {
@@ -407,7 +413,7 @@ int main(int argc, char **argv) {
 
   // Need to initialize an MCInstPrinter as it is
   // required for initializing the MCTargetStreamer
-  // which needs to happen within the CRG.parseCodeRegions() call below.
+  // which needs to happen within the CRG.parseAnalysisRegions() call below.
   // Without an MCTargetStreamer, certain assembly directives can trigger a
   // segfault. (For example, the .cv_fpo_proc directive on x86 will segfault if
   // we don't initialize the MCTargetStreamer.)
@@ -424,9 +430,10 @@ int main(int argc, char **argv) {
   }
 
   // Parse the input and create CodeRegions that llvm-mca can analyze.
-  mca::AsmCodeRegionGenerator CRG(*TheTarget, SrcMgr, Ctx, *MAI, *STI, *MCII);
-  Expected<const mca::CodeRegions &> RegionsOrErr =
-      CRG.parseCodeRegions(std::move(IPtemp));
+  mca::AsmAnalysisRegionGenerator CRG(*TheTarget, SrcMgr, Ctx, *MAI, *STI,
+                                      *MCII);
+  Expected<const mca::AnalysisRegions &> RegionsOrErr =
+      CRG.parseAnalysisRegions(std::move(IPtemp));
   if (!RegionsOrErr) {
     if (auto Err =
             handleErrors(RegionsOrErr.takeError(), [](const StringError &E) {
@@ -437,7 +444,7 @@ int main(int argc, char **argv) {
     }
     return 1;
   }
-  const mca::CodeRegions &Regions = *RegionsOrErr;
+  const mca::AnalysisRegions &Regions = *RegionsOrErr;
 
   // Early exit if errors were found by the code region parsing logic.
   if (!Regions.isValid())
@@ -448,6 +455,39 @@ int main(int argc, char **argv) {
     return 1;
   }
 
+  std::unique_ptr<mca::InstrumentManager> IM;
+  if (!DisableInstrumentManager) {
+    IM = std::unique_ptr<mca::InstrumentManager>(
+        TheTarget->createInstrumentManager(*STI, *MCII));
+  }
+  if (!IM) {
+    // If the target doesn't have its own IM implemented (or the -disable-cb
+    // flag is set) then we use the base class (which does nothing).
+    IM = std::make_unique<mca::InstrumentManager>(*STI, *MCII);
+  }
+
+  // Parse the input and create InstrumentRegion that llvm-mca
+  // can use to improve analysis.
+  mca::AsmInstrumentRegionGenerator IRG(*TheTarget, SrcMgr, Ctx, *MAI, *STI,
+                                        *MCII, *IM);
+  Expected<const mca::InstrumentRegions &> InstrumentRegionsOrErr =
+      IRG.parseInstrumentRegions(std::move(IPtemp));
+  if (!InstrumentRegionsOrErr) {
+    if (auto Err = handleErrors(InstrumentRegionsOrErr.takeError(),
+                                [](const StringError &E) {
+                                  WithColor::error() << E.getMessage() << '\n';
+                                })) {
+      // Default case.
+      WithColor::error() << toString(std::move(Err)) << '\n';
+    }
+    return 1;
+  }
+  const mca::InstrumentRegions &InstrumentRegions = *InstrumentRegionsOrErr;
+
+  // Early exit if errors were found by the instrumentation parsing logic.
+  if (!InstrumentRegions.isValid())
+    return 1;
+
   // Now initialize the output file.
   auto OF = getOutputStream();
   if (std::error_code EC = OF.getError()) {
@@ -491,7 +531,7 @@ int main(int argc, char **argv) {
   }
 
   // Create an instruction builder.
-  mca::InstrBuilder IB(*STI, *MCII, *MRI, MCIA.get());
+  mca::InstrBuilder IB(*STI, *MCII, *MRI, MCIA.get(), *IM);
 
   // Create a context to control ownership of the pipeline hardware.
   mca::Context MCA(*MRI, *STI);
@@ -512,7 +552,7 @@ int main(int argc, char **argv) {
   assert(MAB && "Unable to create asm backend!");
 
   json::Object JSONOutput;
-  for (const std::unique_ptr<mca::CodeRegion> &Region : Regions) {
+  for (const std::unique_ptr<mca::AnalysisRegion> &Region : Regions) {
     // Skip empty code regions.
     if (Region->empty())
       continue;
@@ -527,8 +567,12 @@ int main(int argc, char **argv) {
 
     SmallVector<std::unique_ptr<mca::Instruction>> LoweredSequence;
     for (const MCInst &MCI : Insts) {
+      SMLoc Loc = MCI.getLoc();
+      const SmallVector<mca::SharedInstrument> Instruments =
+          InstrumentRegions.getActiveInstruments(Loc);
+
       Expected<std::unique_ptr<mca::Instruction>> Inst =
-          IB.createInstruction(MCI);
+          IB.createInstruction(MCI, Instruments);
       if (!Inst) {
         if (auto NewE = handleErrors(
                 Inst.takeError(),