[llvm-exegesis] Add predefined floating point values so we can test impact of special values on latency.

Summary: This will be useful to generate many configurations and test instruction regimes (NaN, Inf, subnormal, normal).

Reviewers: courbet

Subscribers: mgorny, tschuett, llvm-commits

Differential Revision: https://reviews.llvm.org/D51858

llvm-svn: 342369

tools/llvm-exegesis/lib/CMakeLists.txt

@@ -20,6 +20,7 @@ add_library(LLVMExegesis
   PerfHelper.cpp
   RegisterAliasing.cpp
   SnippetGenerator.cpp
+  RegisterValue.cpp
   Target.cpp
   Uops.cpp
   )

tools/llvm-exegesis/lib/RegisterValue.cpp

@@ -0,0 +1,48 @@
+//===-- RegisterValue.cpp ---------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RegisterValue.h"
+#include "llvm/ADT/APFloat.h"
+
+namespace exegesis {
+
+static llvm::APFloat getFloatValue(const llvm::fltSemantics &FltSemantics,
+                                   PredefinedValues Value) {
+  switch (Value) {
+  case PredefinedValues::POS_ZERO:
+    return llvm::APFloat::getZero(FltSemantics);
+  case PredefinedValues::NEG_ZERO:
+    return llvm::APFloat::getZero(FltSemantics, true);
+  case PredefinedValues::ONE:
+    return llvm::APFloat(FltSemantics, "1");
+  case PredefinedValues::TWO:
+    return llvm::APFloat(FltSemantics, "2");
+  case PredefinedValues::INF:
+    return llvm::APFloat::getInf(FltSemantics);
+  case PredefinedValues::QNAN:
+    return llvm::APFloat::getQNaN(FltSemantics);
+  case PredefinedValues::SMALLEST_NORM:
+    return llvm::APFloat::getSmallestNormalized(FltSemantics);
+  case PredefinedValues::LARGEST:
+    return llvm::APFloat::getLargest(FltSemantics);
+  case PredefinedValues::ULP:
+    return llvm::APFloat::getSmallest(FltSemantics);
+  case PredefinedValues::ONE_PLUS_ULP:
+    auto Output = getFloatValue(FltSemantics, PredefinedValues::ONE);
+    Output.next(false);
+    return Output;
+  }
+}
+
+llvm::APInt bitcastFloatValue(const llvm::fltSemantics &FltSemantics,
+                              PredefinedValues Value) {
+  return getFloatValue(FltSemantics, Value).bitcastToAPInt();
+}
+
+} // namespace exegesis

tools/llvm-exegesis/lib/RegisterValue.h

@@ -0,0 +1,38 @@
+//===-- RegisterValue.h -----------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///
+/// Defines a Target independent value for a Register. This is useful to explore
+/// the influence of the instruction input values on its execution time.
+///
+//===----------------------------------------------------------------------===//
+
+#include <llvm/ADT/APFloat.h>
+
+namespace exegesis {
+
+enum class PredefinedValues {
+  POS_ZERO,       // Positive zero
+  NEG_ZERO,       // Negative zero
+  ONE,            // 1.0
+  TWO,            // 2.0
+  INF,            // Infinity
+  QNAN,           // Quiet NaN
+  ULP,            // One Unit in the last place
+  SMALLEST = ULP, // The minimum subnormal number
+  SMALLEST_NORM,  // The minimum normal number
+  LARGEST,        // The maximum normal number
+  ONE_PLUS_ULP,   // The value just after 1.0
+};
+
+llvm::APInt bitcastFloatValue(const llvm::fltSemantics &FltSemantics,
+                              PredefinedValues Value);
+
+} // namespace exegesis

unittests/tools/llvm-exegesis/CMakeLists.txt

@@ -15,6 +15,7 @@ add_llvm_unittest(LLVMExegesisTests
   BenchmarkRunnerTest.cpp
   ClusteringTest.cpp
   PerfHelperTest.cpp
+  RegisterValueTest.cpp
   )
 target_link_libraries(LLVMExegesisTests PRIVATE LLVMExegesis)
 

unittests/tools/llvm-exegesis/RegisterValueTest.cpp

@@ -0,0 +1,71 @@
+//===-- RegisterValueTest.cpp -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RegisterValue.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace exegesis {
+
+namespace {
+
+#define CHECK(EXPECTED, ACTUAL)                                                \
+  EXPECT_EQ(llvm::APInt(SizeInBits, EXPECTED, 16),                             \
+            bitcastFloatValue(Semantic, PredefinedValues::ACTUAL))
+
+TEST(RegisterValueTest, Half) {
+  const size_t SizeInBits = 16;
+  const auto &Semantic = llvm::APFloatBase::IEEEhalf();
+  CHECK("0000", POS_ZERO);
+  CHECK("8000", NEG_ZERO);
+  CHECK("3C00", ONE);
+  CHECK("4000", TWO);
+  CHECK("7C00", INF);
+  CHECK("7E00", QNAN);
+  CHECK("7BFF", LARGEST);
+  CHECK("0400", SMALLEST_NORM);
+  CHECK("0001", SMALLEST);
+  CHECK("0001", ULP);
+  CHECK("3C01", ONE_PLUS_ULP);
+}
+
+TEST(RegisterValueTest, Single) {
+  const size_t SizeInBits = 32;
+  const auto &Semantic = llvm::APFloatBase::IEEEsingle();
+  CHECK("00000000", POS_ZERO);
+  CHECK("80000000", NEG_ZERO);
+  CHECK("3F800000", ONE);
+  CHECK("40000000", TWO);
+  CHECK("7F800000", INF);
+  CHECK("7FC00000", QNAN);
+  CHECK("7F7FFFFF", LARGEST);
+  CHECK("00800000", SMALLEST_NORM);
+  CHECK("00000001", SMALLEST);
+  CHECK("00000001", ULP);
+  CHECK("3F800001", ONE_PLUS_ULP);
+}
+
+TEST(RegisterValueTest, Double) {
+  const size_t SizeInBits = 64;
+  const auto &Semantic = llvm::APFloatBase::IEEEdouble();
+  CHECK("0000000000000000", POS_ZERO);
+  CHECK("8000000000000000", NEG_ZERO);
+  CHECK("3FF0000000000000", ONE);
+  CHECK("4000000000000000", TWO);
+  CHECK("7FF0000000000000", INF);
+  CHECK("7FF8000000000000", QNAN);
+  CHECK("7FEFFFFFFFFFFFFF", LARGEST);
+  CHECK("0010000000000000", SMALLEST_NORM);
+  CHECK("0000000000000001", SMALLEST);
+  CHECK("0000000000000001", ULP);
+  CHECK("3FF0000000000001", ONE_PLUS_ULP);
+}
+
+} // namespace
+} // namespace exegesis