[Clang][Driver] Warn on complex number range incompatibility with GCC #144468
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This patch adds a warning for incompatible complex number behavior compared to GCC due to Clang's "last-flag-wins" rule. These were discussed at: https://discourse.llvm.org/t/the-priority-of-fno-fast-math-regarding-complex-number-calculations/84679
s-watanabe314
requested review from
jyknight,
AaronBallman,
MacDue,
andykaylor and
zahiraam
llvmbot
added
clang
|
@llvm/pr-subscribers-clang-driver Author: Shunsuke Watanabe (s-watanabe314) ChangesThis patch adds a warning for incompatible complex number behavior compared to GCC due to Clang's "last-flag-wins" rule. Incompatibilities with GCC occur in the following seven cases. Clang uses the last specified option, but GCC uses an earlier specified option in these seven cases because it has a different option prioritization.
These were discussed at: Full diff: https://github.com/llvm/llvm-project/pull/144468.diff 3 Files Affected:
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 20fb47237c56f..377509cfcf2cd 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -520,6 +520,9 @@ def warn_drv_math_errno_enabled_after_veclib: Warning<
"math errno enabled by '%0' after it was implicitly disabled by '%1',"
" this may limit the utilization of the vector library">,
InGroup<MathErrnoEnabledWithVecLib>;
+def warn_drv_gcc_incompatible_complex_range_override: Warning<
+ "combination of '%0' and '%1' results in complex number calculations incompatible with GCC">,
+ InGroup<GccCompat>;
def note_drv_command_failed_diag_msg : Note<
"diagnostic msg: %0">;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 1d11be1d82be8..244c4c0848aa6 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2915,6 +2915,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
} else {
if (GccRangeComplexOption != "-fno-cx-limited-range")
EmitComplexRangeDiag(D, GccRangeComplexOption, "-fcx-limited-range");
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules" ||
+ GccRangeComplexOption == "-fno-cx-fortran-rules")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
}
GccRangeComplexOption = "-fcx-limited-range";
LastComplexRangeOption = A->getSpelling();
@@ -2929,6 +2934,10 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
GccRangeComplexOption != "-fno-cx-fortran-rules")
EmitComplexRangeDiag(D, GccRangeComplexOption,
"-fno-cx-limited-range");
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
}
GccRangeComplexOption = "-fno-cx-limited-range";
LastComplexRangeOption = A->getSpelling();
@@ -3231,6 +3240,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
case options::OPT_ffast_math:
applyFastMath(true);
LastComplexRangeOption = A->getSpelling();
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules" ||
+ GccRangeComplexOption == "-fno-cx-fortran-rules")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
if (A->getOption().getID() == options::OPT_Ofast)
LastFpContractOverrideOption = "-Ofast";
else
@@ -3255,6 +3269,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
Range != LangOptions::ComplexRangeKind::CX_Full)
EmitComplexRangeDiag(D, LastComplexRangeOption, "-fno-fast-math");
Range = LangOptions::ComplexRangeKind::CX_None;
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules" ||
+ GccRangeComplexOption == "-fcx-limited-range")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
LastComplexRangeOption = "";
GccRangeComplexOption = "";
LastFpContractOverrideOption = "";
diff --git a/clang/test/Driver/range.c b/clang/test/Driver/range.c
index 30140f3c208e0..d86bec46589a1 100644
--- a/clang/test/Driver/range.c
+++ b/clang/test/Driver/range.c
@@ -255,6 +255,31 @@
// RUN: %clang -### -Werror --target=x86_64 -fno-fast-math -ffp-model=strict \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s
+
+// Test incompatibility of complex range override with GCC 14.2.0.
+
+// RUN: %clang -### --target=x86_64 -fcx-limited-range -fno-fast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT1 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -fcx-limited-range \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT2 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -fno-cx-limited-range \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT3 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -ffast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT4 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -fno-fast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT5 %s
+
+// RUN: %clang -### --target=x86_64 -fno-cx-fortran-rules -fcx-limited-range \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT6 %s
+
+// RUN: %clang -### --target=x86_64 -fno-cx-fortran-rules -ffast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT7 %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]
// WARN3: warning: overriding '-fcx-fortran-rules' option with '-fno-cx-limited-range' [-Woverriding-option]
@@ -281,4 +306,12 @@
// CHECK-NOT: -complex-range=improved
// RANGE-NOT: -complex-range=
+// WARN_INCOMPAT1: warning: combination of '-fcx-limited-range' and '-fno-fast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT2: warning: combination of '-fcx-fortran-rules' and '-fcx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT3: warning: combination of '-fcx-fortran-rules' and '-fno-cx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT4: warning: combination of '-fcx-fortran-rules' and '-ffast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT5: warning: combination of '-fcx-fortran-rules' and '-fno-fast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT6: warning: combination of '-fno-cx-fortran-rules' and '-fcx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT7: warning: combination of '-fno-cx-fortran-rules' and '-ffast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+
// ERR: error: unsupported argument 'foo' to option '-fcomplex-arithmetic='
|
|
@llvm/pr-subscribers-clang Author: Shunsuke Watanabe (s-watanabe314) ChangesThis patch adds a warning for incompatible complex number behavior compared to GCC due to Clang's "last-flag-wins" rule. Incompatibilities with GCC occur in the following seven cases. Clang uses the last specified option, but GCC uses an earlier specified option in these seven cases because it has a different option prioritization.
These were discussed at: Full diff: https://github.com/llvm/llvm-project/pull/144468.diff 3 Files Affected:
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 20fb47237c56f..377509cfcf2cd 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -520,6 +520,9 @@ def warn_drv_math_errno_enabled_after_veclib: Warning<
"math errno enabled by '%0' after it was implicitly disabled by '%1',"
" this may limit the utilization of the vector library">,
InGroup<MathErrnoEnabledWithVecLib>;
+def warn_drv_gcc_incompatible_complex_range_override: Warning<
+ "combination of '%0' and '%1' results in complex number calculations incompatible with GCC">,
+ InGroup<GccCompat>;
def note_drv_command_failed_diag_msg : Note<
"diagnostic msg: %0">;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 1d11be1d82be8..244c4c0848aa6 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2915,6 +2915,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
} else {
if (GccRangeComplexOption != "-fno-cx-limited-range")
EmitComplexRangeDiag(D, GccRangeComplexOption, "-fcx-limited-range");
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules" ||
+ GccRangeComplexOption == "-fno-cx-fortran-rules")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
}
GccRangeComplexOption = "-fcx-limited-range";
LastComplexRangeOption = A->getSpelling();
@@ -2929,6 +2934,10 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
GccRangeComplexOption != "-fno-cx-fortran-rules")
EmitComplexRangeDiag(D, GccRangeComplexOption,
"-fno-cx-limited-range");
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
}
GccRangeComplexOption = "-fno-cx-limited-range";
LastComplexRangeOption = A->getSpelling();
@@ -3231,6 +3240,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
case options::OPT_ffast_math:
applyFastMath(true);
LastComplexRangeOption = A->getSpelling();
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules" ||
+ GccRangeComplexOption == "-fno-cx-fortran-rules")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
if (A->getOption().getID() == options::OPT_Ofast)
LastFpContractOverrideOption = "-Ofast";
else
@@ -3255,6 +3269,11 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
Range != LangOptions::ComplexRangeKind::CX_Full)
EmitComplexRangeDiag(D, LastComplexRangeOption, "-fno-fast-math");
Range = LangOptions::ComplexRangeKind::CX_None;
+ // Warn about complex range option overrides incompatible with GCC.
+ if (GccRangeComplexOption == "-fcx-fortran-rules" ||
+ GccRangeComplexOption == "-fcx-limited-range")
+ D.Diag(clang::diag::warn_drv_gcc_incompatible_complex_range_override)
+ << GccRangeComplexOption << A->getSpelling();
LastComplexRangeOption = "";
GccRangeComplexOption = "";
LastFpContractOverrideOption = "";
diff --git a/clang/test/Driver/range.c b/clang/test/Driver/range.c
index 30140f3c208e0..d86bec46589a1 100644
--- a/clang/test/Driver/range.c
+++ b/clang/test/Driver/range.c
@@ -255,6 +255,31 @@
// RUN: %clang -### -Werror --target=x86_64 -fno-fast-math -ffp-model=strict \
// RUN: -c %s 2>&1 | FileCheck --check-prefixes=FULL %s
+
+// Test incompatibility of complex range override with GCC 14.2.0.
+
+// RUN: %clang -### --target=x86_64 -fcx-limited-range -fno-fast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT1 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -fcx-limited-range \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT2 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -fno-cx-limited-range \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT3 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -ffast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT4 %s
+
+// RUN: %clang -### --target=x86_64 -fcx-fortran-rules -fno-fast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT5 %s
+
+// RUN: %clang -### --target=x86_64 -fno-cx-fortran-rules -fcx-limited-range \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT6 %s
+
+// RUN: %clang -### --target=x86_64 -fno-cx-fortran-rules -ffast-math \
+// RUN: -c %s 2>&1 | FileCheck --check-prefixes=WARN_INCOMPAT7 %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]
// WARN3: warning: overriding '-fcx-fortran-rules' option with '-fno-cx-limited-range' [-Woverriding-option]
@@ -281,4 +306,12 @@
// CHECK-NOT: -complex-range=improved
// RANGE-NOT: -complex-range=
+// WARN_INCOMPAT1: warning: combination of '-fcx-limited-range' and '-fno-fast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT2: warning: combination of '-fcx-fortran-rules' and '-fcx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT3: warning: combination of '-fcx-fortran-rules' and '-fno-cx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT4: warning: combination of '-fcx-fortran-rules' and '-ffast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT5: warning: combination of '-fcx-fortran-rules' and '-fno-fast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT6: warning: combination of '-fno-cx-fortran-rules' and '-fcx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+// WARN_INCOMPAT7: warning: combination of '-fno-cx-fortran-rules' and '-ffast-math' results in complex number calculations incompatible with GCC [-Wgcc-compat]
+
// ERR: error: unsupported argument 'foo' to option '-fcomplex-arithmetic='
|
| @@ -520,6 +520,9 @@ def warn_drv_math_errno_enabled_after_veclib: Warning< | |||
| "math errno enabled by '%0' after it was implicitly disabled by '%1'," | |||
| " this may limit the utilization of the vector library">, | |||
| InGroup<MathErrnoEnabledWithVecLib>; | |||
| def warn_drv_gcc_incompatible_complex_range_override: Warning< | |||
| "combination of '%0' and '%1' results in complex number calculations incompatible with GCC">, | |||
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Should we perhaps add note diagnostics or a %select to the warning so we can explain how it's incompatible? I'm worried a user will get this diagnostic and say "okay, great, but... what does that mean and how do I fix that?" and being a bit stuck because they don't know what's incompatible.
There was a problem hiding this comment.
Thank you for the feedback! I agree that a user wouldn't know how to handle this warning just by seeing it. How about adding the following note diagnostic and outputting it along with the incompatibility warning?
note: complex multiplication and division use different calculation methods than GCC. specify '%0' after '%1' for GCC compatibility
Implementing this would result in the following output:
$ clang test.cpp -fcx-fortran-rules -fcx-limited-range
clang: warning: overriding '-fcx-fortran-rules' option with '-fcx-limited-range' [-Woverriding-option]
clang: warning: combination of '-fcx-fortran-rules' and '-fcx-limited-range' results in complex number calculations incompatible with GCC [-Wgcc-compat]
clang: note: complex multiplication and division use different calculation methods than GCC. specify '-fcx-fortran-rules' after '-fcx-limited-range' for GCC compatibility
There was a problem hiding this comment.
A few thoughts:
- It's unfortunate that we emit two warnings for the same thing, especially by default. We really should try to find a way to emit only one warning, I think.
- The "different calculation methods" part of the note doesn't really tell the user all that much, but the important part is the "specify '-blah' after '-yada'" bit and that's good to keep.
WDYT?
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This patch adds a warning for incompatible complex number behavior compared to GCC due to Clang's "last-flag-wins" rule.
Incompatibilities with GCC occur in the following seven cases. Clang uses the last specified option, but GCC uses an earlier specified option in these seven cases because it has a different option prioritization.
These were discussed at:
https://discourse.llvm.org/t/the-priority-of-fno-fast-math-regarding-complex-number-calculations/84679