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| author | Ellis Hoag <ellis.sparky.hoag@gmail.com> | 2022-08-17 06:22:50 -0700 |
|---|---|---|
| committer | Ellis Hoag <ellis.sparky.hoag@gmail.com> | 2022-08-17 06:47:15 -0700 |
| commit | 6f61594d8cd4cca559b3c87f2fa47d4bdc017c82 (patch) | |
| tree | 08ae3fcd035b82d99f43a80ccec1c6fd9bf8c63f | |
| parent | ab6a6b8e0d48087be531171445425a05fc239377 (diff) | |
| download | llvm-6f61594d8cd4cca559b3c87f2fa47d4bdc017c82.zip llvm-6f61594d8cd4cca559b3c87f2fa47d4bdc017c82.tar.gz llvm-6f61594d8cd4cca559b3c87f2fa47d4bdc017c82.tar.bz2 | |
[InstrProf] Add option to avoid instrumenting small functions
If a function only has a few instructions, instrumentation can significantly increase the size and performance overhead of that function. Add the `-pgo-function-size-threshold` option to select a size threshold so these small functions are not instrumented.
A similar option `-fxray-instruction-threshold=<N>` is used for XRay to reduce binary size overhead [1].
[1] https://www.llvm.org/docs/XRay.html
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D131816
| -rw-r--r-- | llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp | 6 | ||||
| -rw-r--r-- | llvm/test/Transforms/PGOProfile/function_size_threshold.ll | 29 |
2 files changed, 35 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp index ca3c4ba..e55a587 100644 --- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp +++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp @@ -292,6 +292,10 @@ static cl::opt<std::string> PGOTraceFuncHash( cl::value_desc("function name"), cl::desc("Trace the hash of the function with this name.")); +static cl::opt<unsigned> PGOFunctionSizeThreshold( + "pgo-function-size-threshold", cl::Hidden, + cl::desc("Do not instrument functions smaller than this threshold")); + namespace llvm { // Command line option to turn on CFG dot dump after profile annotation. // Defined in Analysis/BlockFrequencyInfo.cpp: -pgo-view-counts @@ -1576,6 +1580,8 @@ static bool InstrumentAllFunctions( continue; if (F.hasFnAttribute(llvm::Attribute::SkipProfile)) continue; + if (F.getInstructionCount() < PGOFunctionSizeThreshold) + continue; auto &TLI = LookupTLI(F); auto *BPI = LookupBPI(F); auto *BFI = LookupBFI(F); diff --git a/llvm/test/Transforms/PGOProfile/function_size_threshold.ll b/llvm/test/Transforms/PGOProfile/function_size_threshold.ll new file mode 100644 index 0000000..e1207a6 --- /dev/null +++ b/llvm/test/Transforms/PGOProfile/function_size_threshold.ll @@ -0,0 +1,29 @@ +; RUN: opt < %s -passes=pgo-instr-gen -S | FileCheck %s --implicit-check-not='llvm.instrprof.' --check-prefixes=CHECK,ALL +; RUN: opt < %s -passes=pgo-instr-gen -pgo-function-size-threshold=2 -S | FileCheck %s --implicit-check-not='llvm.instrprof.' --check-prefixes=CHECK,ALL +; RUN: opt < %s -passes=pgo-instr-gen -pgo-function-size-threshold=3 -S | FileCheck %s --implicit-check-not='llvm.instrprof.' +target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +; CHECK-LABEL: define i32 @small( +define i32 @small(i32 %i) { + ; ALL: call void @llvm.instrprof.increment({{.*}}) + %add = add i32 %i, 4 + ret i32 %add +} + +; CHECK-LABEL: define i32 @large( +define i32 @large(i32 %0) { + ; CHECK: call void @llvm.instrprof.increment({{.*}}) + %2 = shl nsw i32 %0, 3 + %3 = or i32 %2, 4 + %4 = mul i32 %3, %0 + %5 = or i32 %4, 3 + %6 = sdiv i32 2, %0 + %7 = add nsw i32 %5, %6 + %8 = mul nsw i32 %0, %0 + %9 = udiv i32 5, %8 + %10 = add nsw i32 %7, %9 + ret i32 %10 +} + +; CHECK: declare void @llvm.instrprof.increment({{.*}}) |