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[clang-cl] Map /Ot to -O3 instead of -O2 #95406

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Jun 14, 2024
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[clang-cl] Map /Ot to -O3 instead of -O2 #95406

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4 changes: 4 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -921,6 +921,10 @@ Android Support
Windows Support
^^^^^^^^^^^^^^^

- The clang-cl ``/Ot`` compiler option ("optimize for speed", also implied by
``/O2``) now maps to clang's ``-O3`` optimizataztion level instead of ``-O2``.
Users who prefer the old behavior can use ``clang-cl /Ot /clang:-O2 ...``.

- Clang-cl now supports function targets with intrinsic headers. This allows
for runtime feature detection of intrinsics. Previously under clang-cl
``immintrin.h`` and similar intrinsic headers would only include the intrinsics
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4 changes: 2 additions & 2 deletions clang/docs/UsersManual.rst
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Expand Up @@ -4636,8 +4636,8 @@ Execute ``clang-cl /?`` to see a list of supported options:
/Og No effect
/Oi- Disable use of builtin functions
/Oi Enable use of builtin functions
/Os Optimize for size
/Ot Optimize for speed
/Os Optimize for size (like clang -Os)
/Ot Optimize for speed (like clang -O3)
/Ox Deprecated (same as /Og /Oi /Ot /Oy /Ob2); use /O2 instead
/Oy- Disable frame pointer omission (x86 only, default)
/Oy Enable frame pointer omission (x86 only)
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4 changes: 2 additions & 2 deletions clang/include/clang/Driver/Options.td
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Expand Up @@ -8279,9 +8279,9 @@ def : CLFlag<"Oi">, Alias<_SLASH_O>, AliasArgs<["i"]>,
def : CLFlag<"Oi-">, Alias<_SLASH_O>, AliasArgs<["i-"]>,
HelpText<"Disable use of builtin functions">;
def : CLFlag<"Os">, Alias<_SLASH_O>, AliasArgs<["s"]>,
HelpText<"Optimize for size">;
HelpText<"Optimize for size (like clang -Os)">;
def : CLFlag<"Ot">, Alias<_SLASH_O>, AliasArgs<["t"]>,
HelpText<"Optimize for speed">;
HelpText<"Optimize for speed (like clang -O3)">;
def : CLFlag<"Ox">, Alias<_SLASH_O>, AliasArgs<["x"]>,
HelpText<"Deprecated (like /Og /Oi /Ot /Oy /Ob2); use /O2">;
def : CLFlag<"Oy">, Alias<_SLASH_O>, AliasArgs<["y"]>,
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4 changes: 2 additions & 2 deletions clang/lib/Driver/ToolChains/MSVC.cpp
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Expand Up @@ -861,7 +861,7 @@ static void TranslateOptArg(Arg *A, llvm::opt::DerivedArgList &DAL,
DAL.AddJoinedArg(A, Opts.getOption(options::OPT_O), "s");
} else if (OptChar == '2' || OptChar == 'x') {
DAL.AddFlagArg(A, Opts.getOption(options::OPT_fbuiltin));
DAL.AddJoinedArg(A, Opts.getOption(options::OPT_O), "2");
DAL.AddJoinedArg(A, Opts.getOption(options::OPT_O), "3");
}
if (SupportsForcingFramePointer &&
!DAL.hasArgNoClaim(options::OPT_fno_omit_frame_pointer))
Expand Down Expand Up @@ -901,7 +901,7 @@ static void TranslateOptArg(Arg *A, llvm::opt::DerivedArgList &DAL,
DAL.AddJoinedArg(A, Opts.getOption(options::OPT_O), "s");
break;
case 't':
DAL.AddJoinedArg(A, Opts.getOption(options::OPT_O), "2");
DAL.AddJoinedArg(A, Opts.getOption(options::OPT_O), "3");
break;
case 'y': {
bool OmitFramePointer = true;
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10 changes: 5 additions & 5 deletions clang/test/Driver/cl-options.c
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Expand Up @@ -189,27 +189,27 @@
// RUN: %clang_cl /Ot --target=i686-pc-windows-msvc -### -- %s 2>&1 | FileCheck -check-prefix=Ot %s
// RUN: %clang_cl /Ot --target=x86_64-pc-windows-msvc -### -- %s 2>&1 | FileCheck -check-prefix=Ot %s
// Ot: -mframe-pointer=none
// Ot: -O2
// Ot: -O3

// RUN: %clang_cl /Ox --target=i686-pc-windows-msvc -### -- %s 2>&1 | FileCheck -check-prefix=Ox %s
// RUN: %clang_cl /Ox --target=x86_64-pc-windows-msvc -### -- %s 2>&1 | FileCheck -check-prefix=Ox %s
// Ox: -mframe-pointer=none
// Ox: -O2
// Ox: -O3

// RUN: %clang_cl --target=i686-pc-win32 /O2sy- -### -- %s 2>&1 | FileCheck -check-prefix=PR24003 %s
// PR24003: -mframe-pointer=all
// PR24003: -Os

// RUN: %clang_cl --target=i686-pc-win32 -Werror -Wno-msvc-not-found /Oy- /O2 -### -- %s 2>&1 | FileCheck -check-prefix=Oy_2 %s
// Oy_2: -mframe-pointer=all
// Oy_2: -O2
// Oy_2: -O3

// RUN: %clang_cl --target=aarch64-pc-windows-msvc -Werror -Wno-msvc-not-found /Oy- /O2 -### -- %s 2>&1 | FileCheck -check-prefix=Oy_aarch64 %s
// Oy_aarch64: -mframe-pointer=non-leaf
// Oy_aarch64: -O2
// Oy_aarch64: -O3

// RUN: %clang_cl --target=i686-pc-win32 -Werror -Wno-msvc-not-found /O2 /O2 -### -- %s 2>&1 | FileCheck -check-prefix=O2O2 %s
// O2O2: "-O2"
// O2O2: "-O3"

// RUN: %clang_cl /Zs -Werror /Oy -- %s 2>&1

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