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Enable fast floating point model and fast debug linking #11466

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8 commits merged into from
Oct 11, 2021
Merged

Enable fast floating point model and fast debug linking #11466

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7c07c3c
Enable fast floating point model and fast debug linking
lhecker Oct 8, 2021
ccff6f6
Introduce ULP based float comparisons
lhecker Oct 8, 2021
ac7c7c2
Fix formatting
lhecker Oct 8, 2021
f92ccba
Fix spellcheck
lhecker Oct 8, 2021
30eede7
Fix build error
lhecker Oct 8, 2021
4948902
Remove accidential comment
lhecker Oct 9, 2021
75441d6
Replaced reinterpret_cast hack with til::bit_cast
lhecker Oct 11, 2021
3971782
Fix build error again
lhecker Oct 11, 2021
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1 change: 1 addition & 0 deletions .github/actions/spelling/allow/math.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -8,3 +8,4 @@ LStep
powf
RSub
sqrtf
ULP
5 changes: 5 additions & 0 deletions src/cascadia/ut_app/ColorHelperTests.cpp
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Expand Up @@ -6,6 +6,9 @@
#include "../TerminalSettingsModel/Profile.h"
#include "../TerminalApp/ColorHelper.h"

// Import some templates to compare floats using approximate matching.
#include <consoletaeftemplates.hpp>

using namespace Microsoft::Console;
using namespace winrt::TerminalApp;
using namespace WEX::Logging;
Expand All @@ -27,6 +30,8 @@ namespace TerminalAppUnitTests

void ColorHelperTests::ConvertHslToRgb()
{
//DebugBreak();
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auto red = winrt::Windows::UI::Colors::Red();
auto redHsl = ColorHelper::RgbToHsl(red);
VERIFY_ARE_EQUAL(0.f, redHsl.H);
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5 changes: 5 additions & 0 deletions src/common.build.pre.props
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Expand Up @@ -119,6 +119,7 @@
<LanguageStandard>stdcpp17</LanguageStandard>
<AdditionalOptions>/utf-8 %(AdditionalOptions)</AdditionalOptions>
<ControlFlowGuard>Guard</ControlFlowGuard>
<FloatingPointModel>Fast</FloatingPointModel>
</ClCompile>
<ResourceCompile>
<PreprocessorDefinitions>EXTERNAL_BUILD;_UNICODE;UNICODE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
Expand All @@ -145,6 +146,10 @@
<Optimization>Disabled</Optimization>
<PreprocessorDefinitions>_DEBUG;DBG;%(PreprocessorDefinitions)</PreprocessorDefinitions>
</ClCompile>
<Link>
<SetChecksum>false</SetChecksum>
<GenerateDebugInformation>DebugFastLink</GenerateDebugInformation>
</Link>
</ItemDefinitionGroup>

<!-- For Release ONLY -->
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39 changes: 39 additions & 0 deletions src/inc/consoletaeftemplates.hpp
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Expand Up @@ -43,6 +43,45 @@ Revision History:

namespace WEX::TestExecution
{
// Compare two floats using a ULP (unit last place) tolerance of up to 4.
// Allows you to compare two floats that are almost equal.
// Think of: 0.200000000000000 vs. 0.200000000000001.
template<typename T, typename U>
bool CompareFloats(T a, T b) noexcept
{
if (std::isnan(a))
{
return std::isnan(b);
}

if (a == b)
{
return true;
}

const auto nDiff = static_cast<std::make_signed_t<U>>(*reinterpret_cast<U*>(&a) - *reinterpret_cast<U*>(&b));
const auto uDiff = static_cast<U>(nDiff < 0 ? -nDiff : nDiff);
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What the heck? This is legal??

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And not UB?

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No this is 100% undefined behavior. But it works because MSVC doesn't do strict aliasing. In C++20 you can use std::bit_cast.

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Regarding the question about legality of reading floats like that: Yeah that's legal, because the bit patterns of IEEE floats are clearly defined.

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I've added til::bit_cast and replaced the reinterpret_cast hack.

return uDiff <= 4;
}

template<>
struct VerifyCompareTraits<float, float>
{
static bool AreEqual(float a, float b) noexcept
{
return CompareFloats<float, uint32_t>(a, b);
}
};

template<>
struct VerifyCompareTraits<double, double>
{
static bool AreEqual(double a, double b) noexcept
{
return CompareFloats<double, uint64_t>(a, b);
}
};

template<>
class VerifyOutputTraits<SMALL_RECT>
{
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2 changes: 1 addition & 1 deletion src/project.inc
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Expand Up @@ -29,7 +29,7 @@ USE_NATIVE_EH = 1
# -------------------------------------

MSC_WARNING_LEVEL = /W4 /WX
USER_C_FLAGS = $(USER_C_FLAGS) /utf-8
USER_C_FLAGS = $(USER_C_FLAGS) /fp:fast /utf-8

# -------------------------------------
# Common Console Includes and Libraries
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