[llvm] [llvm-mca] Add command line option -call-latency (PR #92958)
Chinmay Deshpande via llvm-commits
llvm-commits at lists.llvm.org
Tue May 21 15:52:40 PDT 2024
https://github.com/chinmaydd updated https://github.com/llvm/llvm-project/pull/92958
>From c1d632dfa9be9837614d2cba210ecf30f72aa358 Mon Sep 17 00:00:00 2001
From: Chinmay <cddeshpa at uci.edu>
Date: Tue, 21 May 2024 11:17:56 -0700
Subject: [PATCH 1/3] [llvm-mca] Add command line option -call-latency
Currently we assume a constant latency of 100 cycles for a call
instruction. This commit allows the user to specify a custom value for
the same as a command line argument. Default latency is set to 100.
---
llvm/include/llvm/MCA/InstrBuilder.h | 3 +++
llvm/lib/MCA/InstrBuilder.cpp | 17 +++++++++--------
llvm/tools/llvm-mca/llvm-mca.cpp | 6 ++++++
3 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/llvm/include/llvm/MCA/InstrBuilder.h b/llvm/include/llvm/MCA/InstrBuilder.h
index 3594372489148..49ba8d93ec76f 100644
--- a/llvm/include/llvm/MCA/InstrBuilder.h
+++ b/llvm/include/llvm/MCA/InstrBuilder.h
@@ -78,6 +78,7 @@ class InstrBuilder {
bool FirstCallInst;
bool FirstReturnInst;
+ unsigned CallLatency;
using InstRecycleCallback = std::function<Instruction *(const InstrDesc &)>;
InstRecycleCallback InstRecycleCB;
@@ -111,6 +112,8 @@ class InstrBuilder {
/// or null if there isn't any.
void setInstRecycleCallback(InstRecycleCallback CB) { InstRecycleCB = CB; }
+ void setCallLatency(unsigned CL) { CallLatency = CL; }
+
Expected<std::unique_ptr<Instruction>>
createInstruction(const MCInst &MCI, const SmallVector<Instrument *> &IVec);
};
diff --git a/llvm/lib/MCA/InstrBuilder.cpp b/llvm/lib/MCA/InstrBuilder.cpp
index bcf065c566918..e608fa520fc19 100644
--- a/llvm/lib/MCA/InstrBuilder.cpp
+++ b/llvm/lib/MCA/InstrBuilder.cpp
@@ -33,7 +33,7 @@ InstrBuilder::InstrBuilder(const llvm::MCSubtargetInfo &sti,
const llvm::MCInstrAnalysis *mcia,
const mca::InstrumentManager &im)
: STI(sti), MCII(mcii), MRI(mri), MCIA(mcia), IM(im), FirstCallInst(true),
- FirstReturnInst(true) {
+ FirstReturnInst(true), CallLatency(100U) {
const MCSchedModel &SM = STI.getSchedModel();
ProcResourceMasks.resize(SM.getNumProcResourceKinds());
computeProcResourceMasks(STI.getSchedModel(), ProcResourceMasks);
@@ -220,17 +220,18 @@ static void initializeUsedResources(InstrDesc &ID,
static void computeMaxLatency(InstrDesc &ID, const MCInstrDesc &MCDesc,
const MCSchedClassDesc &SCDesc,
- const MCSubtargetInfo &STI) {
+ const MCSubtargetInfo &STI,
+ unsigned CallLatency) {
if (MCDesc.isCall()) {
// We cannot estimate how long this call will take.
- // Artificially set an arbitrarily high latency (100cy).
- ID.MaxLatency = 100U;
+ // Artificially set an arbitrarily high latency (default: 100cy).
+ ID.MaxLatency = CallLatency;
return;
}
int Latency = MCSchedModel::computeInstrLatency(STI, SCDesc);
- // If latency is unknown, then conservatively assume a MaxLatency of 100cy.
- ID.MaxLatency = Latency < 0 ? 100U : static_cast<unsigned>(Latency);
+ // If latency is unknown, then conservatively assume a MaxLatency set for calls (default: 100cy).
+ ID.MaxLatency = Latency < 0 ? CallLatency : static_cast<unsigned>(Latency);
}
static Error verifyOperands(const MCInstrDesc &MCDesc, const MCInst &MCI) {
@@ -568,7 +569,7 @@ InstrBuilder::createInstrDescImpl(const MCInst &MCI,
// We don't correctly model calls.
WithColor::warning() << "found a call in the input assembly sequence.\n";
WithColor::note() << "call instructions are not correctly modeled. "
- << "Assume a latency of 100cy.\n";
+ << "Assume a latency of " << CallLatency << "cy.\n";
FirstCallInst = false;
}
@@ -580,7 +581,7 @@ InstrBuilder::createInstrDescImpl(const MCInst &MCI,
}
initializeUsedResources(*ID, SCDesc, STI, ProcResourceMasks);
- computeMaxLatency(*ID, MCDesc, SCDesc, STI);
+ computeMaxLatency(*ID, MCDesc, SCDesc, STI, CallLatency);
if (Error Err = verifyOperands(MCDesc, MCI))
return std::move(Err);
diff --git a/llvm/tools/llvm-mca/llvm-mca.cpp b/llvm/tools/llvm-mca/llvm-mca.cpp
index 03d7d7944b9cd..73b704283b8a8 100644
--- a/llvm/tools/llvm-mca/llvm-mca.cpp
+++ b/llvm/tools/llvm-mca/llvm-mca.cpp
@@ -135,6 +135,11 @@ static cl::opt<unsigned>
"(instructions per cycle)"),
cl::cat(ToolOptions), cl::init(0));
+static cl::opt<unsigned>
+ CallLatency("call-latency", cl::Hidden,
+ cl::desc("Number of cycles to assume for a call instruction"),
+ cl::cat(ToolOptions), cl::init(100U));
+
enum class SkipType { NONE, LACK_SCHED, PARSE_FAILURE, ANY_FAILURE };
static cl::opt<enum SkipType> SkipUnsupportedInstructions(
@@ -569,6 +574,7 @@ int main(int argc, char **argv) {
// Create an instruction builder.
mca::InstrBuilder IB(*STI, *MCII, *MRI, MCIA.get(), *IM);
+ IB.setCallLatency(CallLatency);
// Create a context to control ownership of the pipeline hardware.
mca::Context MCA(*MRI, *STI);
>From 2b9fea448c402a4d2830de539760e26990e30513 Mon Sep 17 00:00:00 2001
From: Chinmay <cddeshpa at uci.edu>
Date: Tue, 21 May 2024 15:51:59 -0700
Subject: [PATCH 2/3] [llvm-mca] Move CallLatency in constructor
---
llvm/include/llvm/MCA/InstrBuilder.h | 4 +---
llvm/lib/MCA/InstrBuilder.cpp | 5 +++--
llvm/tools/llvm-mca/llvm-mca.cpp | 3 +--
3 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/llvm/include/llvm/MCA/InstrBuilder.h b/llvm/include/llvm/MCA/InstrBuilder.h
index 49ba8d93ec76f..00c7942e4fa16 100644
--- a/llvm/include/llvm/MCA/InstrBuilder.h
+++ b/llvm/include/llvm/MCA/InstrBuilder.h
@@ -99,7 +99,7 @@ class InstrBuilder {
public:
InstrBuilder(const MCSubtargetInfo &STI, const MCInstrInfo &MCII,
const MCRegisterInfo &RI, const MCInstrAnalysis *IA,
- const InstrumentManager &IM);
+ const InstrumentManager &IM, unsigned CallLatency);
void clear() {
Descriptors.clear();
@@ -112,8 +112,6 @@ class InstrBuilder {
/// or null if there isn't any.
void setInstRecycleCallback(InstRecycleCallback CB) { InstRecycleCB = CB; }
- void setCallLatency(unsigned CL) { CallLatency = CL; }
-
Expected<std::unique_ptr<Instruction>>
createInstruction(const MCInst &MCI, const SmallVector<Instrument *> &IVec);
};
diff --git a/llvm/lib/MCA/InstrBuilder.cpp b/llvm/lib/MCA/InstrBuilder.cpp
index e608fa520fc19..b88248897c294 100644
--- a/llvm/lib/MCA/InstrBuilder.cpp
+++ b/llvm/lib/MCA/InstrBuilder.cpp
@@ -31,9 +31,10 @@ InstrBuilder::InstrBuilder(const llvm::MCSubtargetInfo &sti,
const llvm::MCInstrInfo &mcii,
const llvm::MCRegisterInfo &mri,
const llvm::MCInstrAnalysis *mcia,
- const mca::InstrumentManager &im)
+ const mca::InstrumentManager &im,
+ unsigned cl)
: STI(sti), MCII(mcii), MRI(mri), MCIA(mcia), IM(im), FirstCallInst(true),
- FirstReturnInst(true), CallLatency(100U) {
+ FirstReturnInst(true), CallLatency(cl) {
const MCSchedModel &SM = STI.getSchedModel();
ProcResourceMasks.resize(SM.getNumProcResourceKinds());
computeProcResourceMasks(STI.getSchedModel(), ProcResourceMasks);
diff --git a/llvm/tools/llvm-mca/llvm-mca.cpp b/llvm/tools/llvm-mca/llvm-mca.cpp
index 73b704283b8a8..cc5d4f5fa05de 100644
--- a/llvm/tools/llvm-mca/llvm-mca.cpp
+++ b/llvm/tools/llvm-mca/llvm-mca.cpp
@@ -573,8 +573,7 @@ int main(int argc, char **argv) {
}
// Create an instruction builder.
- mca::InstrBuilder IB(*STI, *MCII, *MRI, MCIA.get(), *IM);
- IB.setCallLatency(CallLatency);
+ mca::InstrBuilder IB(*STI, *MCII, *MRI, MCIA.get(), *IM, CallLatency);
// Create a context to control ownership of the pipeline hardware.
mca::Context MCA(*MRI, *STI);
>From cceff98710bd6a60c222eccbf7fc02a92355eef8 Mon Sep 17 00:00:00 2001
From: Chinmay <cddeshpa at uci.edu>
Date: Tue, 21 May 2024 15:52:26 -0700
Subject: [PATCH 3/3] [llvm-mca] Add LIT test for -call-latency option
---
llvm/test/tools/llvm-mca/X86/call-latency.s | 54 +++++++++++++++++++++
1 file changed, 54 insertions(+)
create mode 100644 llvm/test/tools/llvm-mca/X86/call-latency.s
diff --git a/llvm/test/tools/llvm-mca/X86/call-latency.s b/llvm/test/tools/llvm-mca/X86/call-latency.s
new file mode 100644
index 0000000000000..1f53ded50d186
--- /dev/null
+++ b/llvm/test/tools/llvm-mca/X86/call-latency.s
@@ -0,0 +1,54 @@
+# NOTE: Assertions have been autogenerated by utils/update_mca_test_checks.py
+# RUN: llvm-mca -mtriple=x86_64-unknown-unknown -iterations=1 %s | FileCheck --check-prefixes=ALL,DEFAULT %s
+# RUN: llvm-mca -mtriple=x86_64-unknown-unknown -call-latency=50 -iterations=1 %s | FileCheck --check-prefixes=ALL,CUSTOM %s
+
+callq printf
+
+# ALL: Iterations: 1
+# ALL-NEXT: Instructions: 1
+
+# CUSTOM-NEXT: Total Cycles: 53
+# DEFAULT-NEXT: Total Cycles: 103
+
+# ALL-NEXT: Total uOps: 4
+
+# ALL: Dispatch Width: 6
+
+# CUSTOM-NEXT: uOps Per Cycle: 0.08
+# CUSTOM-NEXT: IPC: 0.02
+
+# DEFAULT-NEXT: uOps Per Cycle: 0.04
+# DEFAULT-NEXT: IPC: 0.01
+
+# ALL-NEXT: Block RThroughput: 1.0
+
+# ALL: Instruction Info:
+# ALL-NEXT: [1]: #uOps
+# ALL-NEXT: [2]: Latency
+# ALL-NEXT: [3]: RThroughput
+# ALL-NEXT: [4]: MayLoad
+# ALL-NEXT: [5]: MayStore
+# ALL-NEXT: [6]: HasSideEffects (U)
+
+# ALL: [1] [2] [3] [4] [5] [6] Instructions:
+# ALL-NEXT: 4 3 1.00 callq printf
+
+# ALL: Resources:
+# ALL-NEXT: [0] - SKLDivider
+# ALL-NEXT: [1] - SKLFPDivider
+# ALL-NEXT: [2] - SKLPort0
+# ALL-NEXT: [3] - SKLPort1
+# ALL-NEXT: [4] - SKLPort2
+# ALL-NEXT: [5] - SKLPort3
+# ALL-NEXT: [6] - SKLPort4
+# ALL-NEXT: [7] - SKLPort5
+# ALL-NEXT: [8] - SKLPort6
+# ALL-NEXT: [9] - SKLPort7
+
+# ALL: Resource pressure per iteration:
+# ALL-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9]
+# ALL-NEXT: - - - - - - 1.00 1.00 1.00 1.00
+
+# ALL: Resource pressure by instruction:
+# ALL-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] Instructions:
+# ALL-NEXT: - - - - - - 1.00 1.00 1.00 1.00 callq printf
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