Controlling Floating Point Behavior
-----------------------------------
-Clang provides a number of ways to control floating point behavior, including
-with command line options and source pragmas. This section
-describes the various floating point semantic modes and the corresponding options.
-
-.. csv-table:: Floating Point Semantic Modes
- :header: "Mode", "Values"
- :widths: 15, 30, 30
-
- "except_behavior", "{ignore, strict, may_trap}", "ffp-exception-behavior"
- "fenv_access", "{off, on}", "(none)"
- "rounding_mode", "{dynamic, tonearest, downward, upward, towardzero}", "frounding-math"
- "contract", "{on, off, fast}", "ffp-contract"
- "denormal_fp_math", "{IEEE, PreserveSign, PositiveZero}", "fdenormal-fp-math"
- "denormal_fp32_math", "{IEEE, PreserveSign, PositiveZero}", "fdenormal-fp-math-fp32"
- "support_math_errno", "{on, off}", "fmath-errno"
- "no_honor_nans", "{on, off}", "fhonor-nans"
- "no_honor_infinities", "{on, off}", "fhonor-infinities"
- "no_signed_zeros", "{on, off}", "fsigned-zeros"
- "allow_reciprocal", "{on, off}", "freciprocal-math"
- "allow_approximate_fns", "{on, off}", "(none)"
- "allow_reassociation", "{on, off}", "fassociative-math"
-
-
-This table describes the option settings that correspond to the three
-floating point semantic models: precise (the default), strict, and fast.
-
-
-.. csv-table:: Floating Point Models
- :header: "Mode", "Precise", "Strict", "Fast"
- :widths: 25, 15, 15, 15
-
- "except_behavior", "ignore", "strict", "ignore"
- "fenv_access", "off", "on", "off"
- "rounding_mode", "tonearest", "dynamic", "tonearest"
- "contract", "on", "off", "fast"
- "denormal_fp_math", "IEEE", "IEEE", "PreserveSign"
- "denormal_fp32_math", "IEEE","IEEE", "PreserveSign"
- "support_math_errno", "on", "on", "off"
- "no_honor_nans", "off", "off", "on"
- "no_honor_infinities", "off", "off", "on"
- "no_signed_zeros", "off", "off", "on"
- "allow_reciprocal", "off", "off", "on"
- "allow_approximate_fns", "off", "off", "on"
- "allow_reassociation", "off", "off", "on"
+Clang provides a number of ways to control floating point behavior. The options
+are listed below.
.. option:: -ffast-math
and ``fast``.
Details:
- * ``precise`` Disables optimizations that are not value-safe on floating-point data, although FP contraction (FMA) is enabled (``-ffp-contract=on``). This is the default behavior.
+ * ``precise`` Disables optimizations that are not value-safe on floating-point data, although FP contraction (FMA) is enabled (``-ffp-contract=fast``). This is the default behavior.
* ``strict`` Enables ``-frounding-math`` and ``-ffp-exception-behavior=strict``, and disables contractions (FMA). All of the ``-ffast-math`` enablements are disabled. Enables ``STDC FENV_ACCESS``: by default ``FENV_ACCESS`` is disabled. This option setting behaves as though ``#pragma STDC FENV_ACESS ON`` appeared at the top of the source file.
* ``fast`` Behaves identically to specifying both ``-ffast-math`` and ``ffp-contract=fast``
llvm::DenormalMode DenormalFPMath = DefaultDenormalFPMath;
llvm::DenormalMode DenormalFP32Math = DefaultDenormalFP32Math;
- StringRef FPContract = "on";
+ StringRef FPContract = "";
bool StrictFPModel = false;
ReciprocalMath = false;
SignedZeros = true;
// -fno_fast_math restores default denormal and fpcontract handling
- FPContract = "on";
+ FPContract = "";
DenormalFPMath = llvm::DenormalMode::getIEEE();
// FIXME: The target may have picked a non-IEEE default mode here based on
// ffp-model= is a Driver option, it is entirely rewritten into more
// granular options before being passed into cc1.
// Use the gcc option in the switch below.
- if (!FPModel.empty() && !FPModel.equals(Val))
+ if (!FPModel.empty() && !FPModel.equals(Val)) {
D.Diag(clang::diag::warn_drv_overriding_flag_option)
<< Args.MakeArgString("-ffp-model=" + FPModel)
<< Args.MakeArgString("-ffp-model=" + Val);
+ FPContract = "";
+ }
if (Val.equals("fast")) {
optID = options::OPT_ffast_math;
FPModel = Val;
- FPContract = Val;
+ FPContract = "fast";
} else if (Val.equals("precise")) {
optID = options::OPT_ffp_contract;
FPModel = Val;
- FPContract = "on";
+ FPContract = "fast";
PreciseFPModel = true;
} else if (Val.equals("strict")) {
StrictFPModel = true;
case options::OPT_ffp_contract: {
StringRef Val = A->getValue();
if (PreciseFPModel) {
- // When -ffp-model=precise is seen on the command line,
- // the boolean PreciseFPModel is set to true which indicates
- // "the current option is actually PreciseFPModel". The optID
- // is changed to OPT_ffp_contract and FPContract is set to "on".
- // the argument Val string is "precise": it shouldn't be checked.
+ // -ffp-model=precise enables ffp-contract=fast as a side effect
+ // the FPContract value has already been set to a string literal
+ // and the Val string isn't a pertinent value.
;
} else if (Val.equals("fast") || Val.equals("on") || Val.equals("off"))
FPContract = Val;
// -fno_fast_math restores default denormal and fpcontract handling
DenormalFPMath = DefaultDenormalFPMath;
DenormalFP32Math = llvm::DenormalMode::getIEEE();
- FPContract = "on";
+ FPContract = "";
break;
}
if (StrictFPModel) {
// If -ffp-model=strict has been specified on command line but
// subsequent options conflict then emit warning diagnostic.
- if (HonorINFs && HonorNaNs && !AssociativeMath && !ReciprocalMath &&
- SignedZeros && TrappingMath && RoundingFPMath &&
- DenormalFPMath == llvm::DenormalMode::getIEEE() &&
- DenormalFP32Math == llvm::DenormalMode::getIEEE() &&
- FPContract.equals("off"))
+ if (HonorINFs && HonorNaNs &&
+ !AssociativeMath && !ReciprocalMath &&
+ SignedZeros && TrappingMath && RoundingFPMath &&
+ (FPContract.equals("off") || FPContract.empty()) &&
+ DenormalFPMath == llvm::DenormalMode::getIEEE() &&
+ DenormalFP32Math == llvm::DenormalMode::getIEEE())
// OK: Current Arg doesn't conflict with -ffp-model=strict
;
else {
-// RUN: %clang_cc1 -O3 -ffp-contract=fast -triple=aarch64-apple-darwin -S -o - %s | FileCheck --check-prefix=CHECK-FMADD %s
+// RUN: %clang_cc1 -O3 -ffp-contract=fast -triple=aarch64-apple-darwin -S -o - %s | FileCheck %s
// REQUIRES: aarch64-registered-target
float fma_test1(float a, float b, float c) {
-// CHECK-FMADD: fmadd
- float x = a * b;
- float y = x + c;
- return y;
-}
-
-// RUN: %clang_cc1 -triple=x86_64 %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-DEFAULT %s
-//
-// RUN: %clang_cc1 -triple=x86_64 -ffp-contract=off %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-DEFAULT %s
-// RUN: %clang_cc1 -triple=x86_64 -ffp-contract=on %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-ON %s
-// RUN: %clang_cc1 -triple=x86_64 -ffp-contract=fast %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-CONTRACTFAST %s
-//
-// RUN: %clang_cc1 -triple=x86_64 -ffast-math %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-DEFAULTFAST %s
-// RUN: %clang_cc1 -triple=x86_64 -ffast-math -ffp-contract=off %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-DEFAULTFAST %s
-// RUN: %clang_cc1 -triple=x86_64 -ffast-math -ffp-contract=on %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-ONFAST %s
-// RUN: %clang_cc1 -triple=x86_64 -ffast-math -ffp-contract=fast %s -emit-llvm -o - \
-// RUN:| FileCheck --check-prefix=CHECK-FASTFAST %s
-float mymuladd( float x, float y, float z ) {
- return x * y + z;
- // CHECK-DEFAULT: = fmul float
- // CHECK-DEFAULT: = fadd float
-
- // CHECK-ON: = call float @llvm.fmuladd.f32
-
- // CHECK-CONTRACTFAST: = fmul contract float
- // CHECK-CONTRACTFAST: = fadd contract float
-
- // CHECK-DEFAULTFAST: = fmul reassoc nnan ninf nsz arcp afn float
- // CHECK-DEFAULTFAST: = fadd reassoc nnan ninf nsz arcp afn float
-
- // CHECK-ONFAST: = call reassoc nnan ninf nsz arcp afn float @llvm.fmuladd.f32
-
- // CHECK-FASTFAST: = fmul fast float
- // CHECK-FASTFAST: = fadd fast float
+// CHECK: fmadd
+ float x = a * b;
+ float y = x + c;
+ return y;
}
// REQUIRES: powerpc-registered-target
// RUN: %clang -S -emit-llvm -target powerpc64-unknown-linux-gnu -mcpu=pwr8 -ffreestanding -DNO_WARN_X86_INTRINSICS %s \
-// RUN: -ffp-contract=off -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-BE
+// RUN: -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-BE
// RUN: %clang -S -emit-llvm -target powerpc64le-unknown-linux-gnu -mcpu=pwr8 -ffreestanding -DNO_WARN_X86_INTRINSICS %s \
-// RUN: -ffp-contract=off -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-LE
+// RUN: -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-LE
// CHECK-BE-DAG: @_mm_movemask_pd.perm_mask = internal constant <4 x i32> <i32 -2139062144, i32 -2139062144, i32 -2139062144, i32 -2139078656>, align 16
// CHECK-BE-DAG: @_mm_shuffle_epi32.permute_selectors = internal constant [4 x i32] [i32 66051, i32 67438087, i32 134810123, i32 202182159], align 4
// REQUIRES: powerpc-registered-target
// RUN: %clang -S -emit-llvm -target powerpc64-unknown-linux-gnu -mcpu=pwr8 -ffreestanding -DNO_WARN_X86_INTRINSICS %s \
-// RUN: -ffp-contract=off -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-BE
+// RUN: -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-BE
// RUN: %clang -x c++ -fsyntax-only -target powerpc64-unknown-linux-gnu -mcpu=pwr8 -ffreestanding -DNO_WARN_X86_INTRINSICS %s \
// RUN: -fno-discard-value-names -mllvm -disable-llvm-optzns
// RUN: %clang -S -emit-llvm -target powerpc64le-unknown-linux-gnu -mcpu=pwr8 -ffreestanding -DNO_WARN_X86_INTRINSICS %s \
-// RUN: -ffp-contract=off -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-LE
+// RUN: -fno-discard-value-names -mllvm -disable-llvm-optzns -o - | llvm-cxxfilt -n | FileCheck %s --check-prefixes=CHECK,CHECK-LE
// RUN: %clang -x c++ -fsyntax-only -target powerpc64le-unknown-linux-gnu -mcpu=pwr8 -ffreestanding -DNO_WARN_X86_INTRINSICS %s \
// RUN: -fno-discard-value-names -mllvm -disable-llvm-optzns
// Test that incompatible combinations of -ffp-model= options
// and other floating point options get a warning diagnostic.
+//
+// REQUIRES: clang-driver
-// RUN: %clang -target x86_64 -### -ffp-model=fast -ffp-contract=off -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=fast -ffp-contract=off -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN %s
// WARN: warning: overriding '-ffp-model=fast' option with '-ffp-contract=off' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=fast -ffp-contract=on -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=fast -ffp-contract=on -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN1 %s
// WARN1: warning: overriding '-ffp-model=fast' option with '-ffp-contract=on' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fassociative-math -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fassociative-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN2 %s
// WARN2: warning: overriding '-ffp-model=strict' option with '-fassociative-math' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -ffast-math -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -ffast-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN3 %s
// WARN3: warning: overriding '-ffp-model=strict' option with '-ffast-math' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -ffinite-math-only -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -ffinite-math-only -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN4 %s
// WARN4: warning: overriding '-ffp-model=strict' option with '-ffinite-math-only' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -ffp-contract=fast -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -ffp-contract=fast -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN5 %s
// WARN5: warning: overriding '-ffp-model=strict' option with '-ffp-contract=fast' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -ffp-contract=fast -c %s 2>&1 \
-// RUN: | FileCheck --check-prefix=WARN6 %s
-// WARN6: warning: overriding '-ffp-model=strict' option with '-ffp-contract=fast' [-Woverriding-t-option]
-
-// RUN: %clang -target x86_64 -### -ffp-model=strict -ffp-contract=on -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -ffp-contract=on -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN7 %s
// WARN7: warning: overriding '-ffp-model=strict' option with '-ffp-contract=on' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fno-honor-infinities -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fno-honor-infinities -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN8 %s
// WARN8: warning: overriding '-ffp-model=strict' option with '-fno-honor-infinities' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fno-honor-nans -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fno-honor-nans -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN9 %s
// WARN9: warning: overriding '-ffp-model=strict' option with '-fno-honor-nans' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fno-rounding-math -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fno-rounding-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARNa %s
// WARNa: warning: overriding '-ffp-model=strict' option with '-fno-rounding-math' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fno-signed-zeros -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fno-signed-zeros -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARNb %s
// WARNb: warning: overriding '-ffp-model=strict' option with '-fno-signed-zeros' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fno-trapping-math -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fno-trapping-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARNc %s
// WARNc: warning: overriding '-ffp-model=strict' option with '-fno-trapping-math' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -freciprocal-math -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -freciprocal-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARNd %s
// WARNd: warning: overriding '-ffp-model=strict' option with '-freciprocal-math' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -funsafe-math-optimizations -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -funsafe-math-optimizations -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARNe %s
// WARNe: warning: overriding '-ffp-model=strict' option with '-funsafe-math-optimizations' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -Ofast -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -Ofast -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARNf %s
// WARNf: warning: overriding '-ffp-model=strict' option with '-Ofast' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -ffp-model=strict -fdenormal-fp-math=preserve-sign,preserve-sign -c %s 2>&1 \
+// RUN: %clang -### -ffp-model=strict -fdenormal-fp-math=preserve-sign,preserve-sign -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=WARN10 %s
// WARN10: warning: overriding '-ffp-model=strict' option with '-fdenormal-fp-math=preserve-sign,preserve-sign' [-Woverriding-t-option]
-// RUN: %clang -target x86_64 -### -c %s 2>&1 \
+// RUN: %clang -### -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-NOROUND %s
// CHECK-NOROUND: "-cc1"
// CHECK-NOROUND: "-fno-rounding-math"
-// RUN: %clang -target x86_64 -### -frounding-math -c %s 2>&1 \
+// RUN: %clang -### -frounding-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-ROUND --implicit-check-not ffp-exception-behavior=strict %s
// CHECK-ROUND: "-cc1"
// CHECK-ROUND: "-frounding-math"
-// RUN: %clang -target x86_64 -### -ftrapping-math -c %s 2>&1 \
+// RUN: %clang -### -ftrapping-math -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-TRAP %s
// CHECK-TRAP: "-cc1"
// CHECK-TRAP: "-ffp-exception-behavior=strict"
-// RUN: %clang -target x86_64 -### -nostdinc -ffp-model=fast -c %s 2>&1 \
+// RUN: %clang -### -nostdinc -ffp-model=fast -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-FPM-FAST %s
// CHECK-FPM-FAST: "-cc1"
// CHECK-FPM-FAST: "-menable-no-infs"
// CHECK-FPM-FAST: "-ffast-math"
// CHECK-FPM-FAST: "-ffinite-math-only"
-// RUN: %clang -target x86_64 -### -nostdinc -ffp-model=precise -c %s 2>&1 \
+// RUN: %clang -### -nostdinc -ffp-model=precise -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-FPM-PRECISE %s
// CHECK-FPM-PRECISE: "-cc1"
-// CHECK-FPM-PRECISE: "-ffp-contract=on"
+// CHECK-FPM-PRECISE: "-ffp-contract=fast"
// CHECK-FPM-PRECISE: "-fno-rounding-math"
-// RUN: %clang -target x86_64 -### -nostdinc -ffp-model=strict -c %s 2>&1 \
+// RUN: %clang -### -nostdinc -ffp-model=strict -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-FPM-STRICT %s
// CHECK-FPM-STRICT: "-cc1"
-// CHECK-FPM-STRICT: "-fmath-errno"
-// CHECK-FPM-STRICT: "-ffp-contract=off"
// CHECK-FPM-STRICT: "-frounding-math"
// CHECK-FPM-STRICT: "-ffp-exception-behavior=strict"
-// RUN: %clang -target x86_64 -### -nostdinc -ffp-exception-behavior=strict -c %s 2>&1 \
+// RUN: %clang -### -nostdinc -ffp-exception-behavior=strict -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-FEB-STRICT %s
// CHECK-FEB-STRICT: "-cc1"
// CHECK-FEB-STRICT: "-fno-rounding-math"
// CHECK-FEB-STRICT: "-ffp-exception-behavior=strict"
-// RUN: %clang -target x86_64 -### -nostdinc -ffp-exception-behavior=maytrap -c %s 2>&1 \
+// RUN: %clang -### -nostdinc -ffp-exception-behavior=maytrap -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-FEB-MAYTRAP %s
// CHECK-FEB-MAYTRAP: "-cc1"
// CHECK-FEB-MAYTRAP: "-fno-rounding-math"
// CHECK-FEB-MAYTRAP: "-ffp-exception-behavior=maytrap"
-// RUN: %clang -target x86_64 -### -nostdinc -ffp-exception-behavior=ignore -c %s 2>&1 \
+// RUN: %clang -### -nostdinc -ffp-exception-behavior=ignore -c %s 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-FEB-IGNORE %s
// CHECK-FEB-IGNORE: "-cc1"
// CHECK-FEB-IGNORE: "-fno-rounding-math"
// CHECK-FEB-IGNORE: "-ffp-exception-behavior=ignore"
+