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[Clang][Driver] Override complex number calculation method by -fno-fast-math #132680

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s-watanabe314 merged 4 commits into from
Jun 12, 2025
Merged

[Clang][Driver] Override complex number calculation method by -fno-fast-math #132680

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9265cb9
[Clang][Driver] Override complex number calculation method by -fno-fa…
s-watanabe314 Mar 14, 2025
b0e198b
Add test cases where -fno-fast-math is specified first
s-watanabe314 Mar 26, 2025
8b947e2
Fix warning message and condition
s-watanabe314 Jun 3, 2025
7a5ab14
Fix initialization of std::string variables related to the complex ra…
s-watanabe314 Jun 11, 2025
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22 changes: 21 additions & 1 deletion clang/lib/Driver/ToolChains/Clang.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2997,6 +2997,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
LangOptions::ComplexRangeKind Range = LangOptions::ComplexRangeKind::CX_None;
std::string ComplexRangeStr = "";
std::string GccRangeComplexOption = "";
std::string LastComplexRangeOption = "";
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@andykaylor andykaylor Mar 24, 2025

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I don't think I remember during our Discourse discussion of this that there was already a GccRangeComplexOption variable here. Do we really need another variable? If you just set GccRangeComplexOption to empty for -ffast-math and -fno-fast-math, would that give us reasonable diagnostics?

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@s-watanabe314 s-watanabe314 Mar 26, 2025

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Thank you for your feedback!

If you just set GccRangeComplexOption to empty for -ffast-math and -fno-fast-math, would that give us reasonable diagnostics?

I think it's difficult. I believe diagnostics should be emitted when Range specified with options other than -ffast-math is overridden by -fno-fast-math. To distinguish between these cases, I think we need a variable that determines what options, including Clang-specific options, were specified before -fno-fast-math. Even if we empty GccRangeComplexOption when -ffast-math is spcified, it's impossible to distinguish whether the preceding option before -fno-fast-math was -ffast-math or -fcomplex-arithmetic=basic. If it's acceptable to assign "-ffp-model" or "-fcomplex-arithmetic" to GccRangeComplexOption, then a new variable might not be necessary.

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@MaskRay MaskRay Apr 2, 2025

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std::string LastComplexRangeOption default initialization

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@s-watanabe314 s-watanabe314 Apr 3, 2025

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Does this mean that = "" is unnecessary? I initialized it in the same way as GccRangeComplexOption, but should I remove it?

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@MaskRay MaskRay May 30, 2025

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= "" is unnecessary. The newly introduced variable can drop = "". You can also drop = "" for the two existing variables as this is minor change.


auto setComplexRange = [&](LangOptions::ComplexRangeKind NewRange) {
// Warn if user expects to perform full implementation of complex
Expand All @@ -3015,7 +3016,12 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
if (Aggressive) {
HonorINFs = false;
HonorNaNs = false;
setComplexRange(LangOptions::ComplexRangeKind::CX_Basic);
// If the last specified option related to complex range is
// -fno-fast-math, override 'Range' without warning.
if (LastComplexRangeOption == "-fno-fast-math")
Range = LangOptions::ComplexRangeKind::CX_Basic;
else
setComplexRange(LangOptions::ComplexRangeKind::CX_Basic);
} else {
HonorINFs = true;
HonorNaNs = true;
Expand Down Expand Up @@ -3080,6 +3086,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
EmitComplexRangeDiag(D, GccRangeComplexOption, "-fcx-limited-range");
}
GccRangeComplexOption = "-fcx-limited-range";
LastComplexRangeOption = "-fcx-limited-range";
Range = LangOptions::ComplexRangeKind::CX_Basic;
break;
case options::OPT_fno_cx_limited_range:
Expand All @@ -3093,6 +3100,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
"-fno-cx-limited-range");
}
GccRangeComplexOption = "-fno-cx-limited-range";
LastComplexRangeOption = "-fno-cx-limited-range";
Range = LangOptions::ComplexRangeKind::CX_Full;
break;
case options::OPT_fcx_fortran_rules:
Expand All @@ -3102,6 +3110,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
else
EmitComplexRangeDiag(D, GccRangeComplexOption, "-fcx-fortran-rules");
GccRangeComplexOption = "-fcx-fortran-rules";
LastComplexRangeOption = "-fcx-fortran-rules";
Range = LangOptions::ComplexRangeKind::CX_Improved;
break;
case options::OPT_fno_cx_fortran_rules:
Expand All @@ -3114,6 +3123,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
"-fno-cx-fortran-rules");
}
GccRangeComplexOption = "-fno-cx-fortran-rules";
LastComplexRangeOption = "-fno-cx-fortran-rules";
Range = LangOptions::ComplexRangeKind::CX_Full;
break;
case options::OPT_fcomplex_arithmetic_EQ: {
Expand Down Expand Up @@ -3148,6 +3158,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
ComplexArithmeticStr(RangeVal));
}
}
LastComplexRangeOption = "-fcomplex-arithmetic";
Range = RangeVal;
break;
}
Expand Down Expand Up @@ -3201,6 +3212,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
} else
D.Diag(diag::err_drv_unsupported_option_argument)
<< A->getSpelling() << Val;
LastComplexRangeOption = "-ffp-model";
break;
}

Expand Down Expand Up @@ -3386,6 +3398,7 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
[[fallthrough]];
case options::OPT_ffast_math:
applyFastMath(true);
LastComplexRangeOption = "-ffast-math";
if (A->getOption().getID() == options::OPT_Ofast)
LastFpContractOverrideOption = "-Ofast";
else
Expand All @@ -3403,6 +3416,13 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
ApproxFunc = false;
SignedZeros = true;
restoreFPContractState();
// If the last specified option related to complex range is -ffast-math,
// override 'Range' without warning.
if (LastComplexRangeOption == "-ffast-math")
Range = LangOptions::ComplexRangeKind::CX_Full;
else
setComplexRange(LangOptions::ComplexRangeKind::CX_Full);
LastComplexRangeOption = "-fno-fast-math";
LastFpContractOverrideOption = "";
break;
} // End switch (A->getOption().getID())
Expand Down
61 changes: 53 additions & 8 deletions clang/test/Driver/range.c
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Expand Up @@ -177,14 +177,45 @@
// RUN: %clang -### -target x86_64 -ffast-math -fcomplex-arithmetic=basic -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=BASIC %s

// BASIC: -complex-range=basic
// FULL: -complex-range=full
// PRMTD: -complex-range=promoted
// BASIC-NOT: -complex-range=improved
// CHECK-NOT: -complex-range=basic
// IMPRVD: -complex-range=improved
// IMPRVD-NOT: -complex-range=basic
// CHECK-NOT: -complex-range=improved
// RUN: %clang -### -target x86_64 -fcx-limited-range -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN21 %s

// RUN: %clang -### -Werror -target x86_64 -fno-cx-limited-range -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s

// RUN: %clang -### -target x86_64 -fcx-fortran-rules -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN22 %s

// RUN: %clang -### -Werror -target x86_64 -fno-cx-fortran-rules -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s

// RUN: %clang -### -Werror -target x86_64 -ffast-math -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s

// RUN: %clang -### -target x86_64 -fcomplex-arithmetic=basic -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN23 %s

// RUN: %clang -### -target x86_64 -fcomplex-arithmetic=promoted -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN24 %s

// RUN: %clang -### -target x86_64 -fcomplex-arithmetic=improved -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN25 %s

// RUN: %clang -### -Werror -target x86_64 -fcomplex-arithmetic=full -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s

// RUN: %clang -### -target x86_64 -ffp-model=aggressive -fno-fast-math \
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@andykaylor andykaylor Apr 1, 2025

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I'm not sure this should result in a warning, and if it does the fact that the warning is about complex is likely to confuse some users. The test is checking for this:

warning: overriding '-fcomplex-arithmetic=basic' option with '-fcomplex-arithmetic=full' [-Woverriding-option]

But neither of those options was explicitly used.

// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN23 %s

// RUN: %clang -### -target x86_64 -ffp-model=fast -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL,WARN24 %s
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@andykaylor andykaylor Apr 1, 2025

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As above, I don't think there should be a warning here.


// RUN: %clang -### -Werror -target x86_64 -ffp-model=precise -fno-fast-math \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s

// RUN: %clang -### -Werror -target x86_64 -ffp-model=strict -fno-fast-math \
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@andykaylor andykaylor Mar 24, 2025

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Can you add test cases for when -fno-fast-math is followed by other options that change the complex mode?

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@s-watanabe314 s-watanabe314 Mar 26, 2025

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I added test cases.

// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s


// WARN1: warning: overriding '-fcx-limited-range' option with '-fcx-fortran-rules' [-Woverriding-option]
// WARN2: warning: overriding '-fno-cx-limited-range' option with '-fcx-fortran-rules' [-Woverriding-option]
Expand All @@ -196,5 +227,19 @@
// WARN14: overriding '-complex-range=promoted' option with '-fcx-limited-range' [-Woverriding-option]
// WARN17: warning: overriding '-fcomplex-arithmetic=full' option with '-fcomplex-arithmetic=basic' [-Woverriding-option]
// WARN20: warning: overriding '-fcx-fortran-rules' option with '-fcx-limited-range' [-Woverriding-option]
// WARN21: warning: overriding '-fcx-limited-range' option with '-fcomplex-arithmetic=full' [-Woverriding-option]
// WARN22: warning: overriding '-fcx-fortran-rules' option with '-fcomplex-arithmetic=full' [-Woverriding-option]
// WARN23: warning: overriding '-fcomplex-arithmetic=basic' option with '-fcomplex-arithmetic=full' [-Woverriding-option]
// WARN24: warning: overriding '-fcomplex-arithmetic=promoted' option with '-fcomplex-arithmetic=full' [-Woverriding-option]
// WARN25: warning: overriding '-fcomplex-arithmetic=improved' option with '-fcomplex-arithmetic=full' [-Woverriding-option]

// BASIC: -complex-range=basic
// FULL: -complex-range=full
// PRMTD: -complex-range=promoted
// BASIC-NOT: -complex-range=improved
// CHECK-NOT: -complex-range=basic
// IMPRVD: -complex-range=improved
// IMPRVD-NOT: -complex-range=basic
// CHECK-NOT: -complex-range=improved

// ERR: error: unsupported argument 'foo' to option '-fcomplex-arithmetic='