[Driver] Restructure handling of -ffast-math and similar options

The way -ffast-math and the various related options to tweak floating-point
handling are handled is inflexible and rather confusing. This patch restructures
things so that we go through the options adjusting our idea of what's enabled as
we go, instead of trying to figure each individual thing out by working
backwards from the end, as this makes the behaviour of each individual option
more clear.

Doing it this way also means we get gcc-compatible behaviour for when the
__FAST_MATH__ and __FINITE_MATH_ONLY__ macros are defined, as they should depend
on the final set of features that are enabled and not just on -ffast-math and
-ffinite-math-only specifically.

Differential Revision: http://reviews.llvm.org/D30582

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@297837 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Driver/ToolChains/Clang.cpp b/lib/Driver/ToolChains/Clang.cpp
index fcb8c3ede11686e8cc2df7abb6ef40db0c4421eb..d23ccc1244b0014bb484f6877c388c6dc4b7b48d 100644 (file)
--- a/lib/Driver/ToolChains/Clang.cpp
+++ b/lib/Driver/ToolChains/Clang.cpp
@@ -2301,98 +2301,129 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Args.hasArg(options::OPT_fsplit_stack))
     CmdArgs.push_back("-split-stacks");
 
-  // If -Ofast is the optimization level, then -ffast-math should be enabled.
-  // This alias option is being used to simplify the getLastArg logic.
-  OptSpecifier FastMathAliasOption =
-      OFastEnabled ? options::OPT_Ofast : options::OPT_ffast_math;
-
   // Handle various floating point optimization flags, mapping them to the
-  // appropriate LLVM code generation flags. The pattern for all of these is to
-  // default off the codegen optimizations, and if any flag enables them and no
-  // flag disables them after the flag enabling them, enable the codegen
-  // optimization. This is complicated by several "umbrella" flags.
-  if (Arg *A = Args.getLastArg(
-          options::OPT_ffast_math, FastMathAliasOption,
-          options::OPT_fno_fast_math, options::OPT_ffinite_math_only,
-          options::OPT_fno_finite_math_only, options::OPT_fhonor_infinities,
-          options::OPT_fno_honor_infinities))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_finite_math_only &&
-        A->getOption().getID() != options::OPT_fhonor_infinities)
-      CmdArgs.push_back("-menable-no-infs");
-  if (Arg *A = Args.getLastArg(
-          options::OPT_ffast_math, FastMathAliasOption,
-          options::OPT_fno_fast_math, options::OPT_ffinite_math_only,
-          options::OPT_fno_finite_math_only, options::OPT_fhonor_nans,
-          options::OPT_fno_honor_nans))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_finite_math_only &&
-        A->getOption().getID() != options::OPT_fhonor_nans)
-      CmdArgs.push_back("-menable-no-nans");
-
+  // appropriate LLVM code generation flags. This is complicated by several
+  // "umbrella" flags, so we do this by stepping through the flags incrementally
+  // adjusting what we think is enabled/disabled, then at the end settting the
+  // LLVM flags based on the final state.
+  bool HonorInfs = true;
+  bool HonorNans = true;
   // -fmath-errno is the default on some platforms, e.g. BSD-derived OSes.
   bool MathErrno = getToolChain().IsMathErrnoDefault();
-  if (Arg *A =
-          Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
-                          options::OPT_fno_fast_math, options::OPT_fmath_errno,
-                          options::OPT_fno_math_errno)) {
-    // Turning on -ffast_math (with either flag) removes the need for MathErrno.
-    // However, turning *off* -ffast_math merely restores the toolchain default
-    // (which may be false).
-    if (A->getOption().getID() == options::OPT_fno_math_errno ||
-        A->getOption().getID() == options::OPT_ffast_math ||
-        A->getOption().getID() == options::OPT_Ofast)
-      MathErrno = false;
-    else if (A->getOption().getID() == options::OPT_fmath_errno)
-      MathErrno = true;
-  }
-  if (MathErrno)
-    CmdArgs.push_back("-fmath-errno");
-
-  // There are several flags which require disabling very specific
-  // optimizations. Any of these being disabled forces us to turn off the
-  // entire set of LLVM optimizations, so collect them through all the flag
-  // madness.
   bool AssociativeMath = false;
-  if (Arg *A = Args.getLastArg(
-          options::OPT_ffast_math, FastMathAliasOption,
-          options::OPT_fno_fast_math, options::OPT_funsafe_math_optimizations,
-          options::OPT_fno_unsafe_math_optimizations,
-          options::OPT_fassociative_math, options::OPT_fno_associative_math))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
-        A->getOption().getID() != options::OPT_fno_associative_math)
-      AssociativeMath = true;
   bool ReciprocalMath = false;
-  if (Arg *A = Args.getLastArg(
-          options::OPT_ffast_math, FastMathAliasOption,
-          options::OPT_fno_fast_math, options::OPT_funsafe_math_optimizations,
-          options::OPT_fno_unsafe_math_optimizations,
-          options::OPT_freciprocal_math, options::OPT_fno_reciprocal_math))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
-        A->getOption().getID() != options::OPT_fno_reciprocal_math)
-      ReciprocalMath = true;
   bool SignedZeros = true;
-  if (Arg *A = Args.getLastArg(
-          options::OPT_ffast_math, FastMathAliasOption,
-          options::OPT_fno_fast_math, options::OPT_funsafe_math_optimizations,
-          options::OPT_fno_unsafe_math_optimizations,
-          options::OPT_fsigned_zeros, options::OPT_fno_signed_zeros))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
-        A->getOption().getID() != options::OPT_fsigned_zeros)
-      SignedZeros = false;
   bool TrappingMath = true;
-  if (Arg *A = Args.getLastArg(
-          options::OPT_ffast_math, FastMathAliasOption,
-          options::OPT_fno_fast_math, options::OPT_funsafe_math_optimizations,
-          options::OPT_fno_unsafe_math_optimizations,
-          options::OPT_ftrapping_math, options::OPT_fno_trapping_math))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations &&
-        A->getOption().getID() != options::OPT_ftrapping_math)
+  StringRef DenormalFpMath = "";
+  StringRef FpContract = "";
+
+  for (Arg *A : Args) {
+    switch (A->getOption().getID()) {
+    // If this isn't an FP option skip the claim below
+    default:
+      continue;
+
+    // Options controlling individual features
+    case options::OPT_fhonor_infinities:    HonorInfs = true;        break;
+    case options::OPT_fno_honor_infinities: HonorInfs = false;       break;
+    case options::OPT_fhonor_nans:          HonorNans = true;        break;
+    case options::OPT_fno_honor_nans:       HonorNans = false;       break;
+    case options::OPT_fmath_errno:          MathErrno = true;        break;
+    case options::OPT_fno_math_errno:       MathErrno = false;       break;
+    case options::OPT_fassociative_math:    AssociativeMath = true;  break;
+    case options::OPT_fno_associative_math: AssociativeMath = false; break;
+    case options::OPT_freciprocal_math:     ReciprocalMath = true;   break;
+    case options::OPT_fno_reciprocal_math:  ReciprocalMath = false;  break;
+    case options::OPT_fsigned_zeros:        SignedZeros = true;      break;
+    case options::OPT_fno_signed_zeros:     SignedZeros = false;     break;
+    case options::OPT_ftrapping_math:       TrappingMath = true;     break;
+    case options::OPT_fno_trapping_math:    TrappingMath = false;    break;
+
+    case options::OPT_fdenormal_fp_math_EQ:
+      DenormalFpMath = A->getValue();
+      break;
+
+    // Validate and pass through -fp-contract option.
+    case options::OPT_ffp_contract: {
+      StringRef Val = A->getValue();
+      if (Val == "fast" || Val == "on" || Val == "off") {
+        FpContract = Val;
+      } else {
+        D.Diag(diag::err_drv_unsupported_option_argument)
+            << A->getOption().getName() << Val;
+      }
+      break;
+    }
+
+    case options::OPT_ffinite_math_only:
+      HonorInfs = false;
+      HonorNans = false;
+      break;
+    case options::OPT_fno_finite_math_only:
+      HonorInfs = true;
+      HonorNans = true;
+      break;
+
+    case options::OPT_funsafe_math_optimizations:
+      AssociativeMath = true;
+      ReciprocalMath = true;
+      SignedZeros = false;
+      TrappingMath = false;
+      break;
+    case options::OPT_fno_unsafe_math_optimizations:
+      AssociativeMath = false;
+      ReciprocalMath = false;
+      SignedZeros = true;
+      TrappingMath = true;
+      // -fno_unsafe_math_optimizations restores default denormal handling
+      DenormalFpMath = "";
+      break;
+
+    case options::OPT_Ofast:
+      // If -Ofast is the optimization level, then -ffast-math should be enabled
+      if (!OFastEnabled)
+        continue;
+      LLVM_FALLTHROUGH;
+    case options::OPT_ffast_math:
+      HonorInfs = false;
+      HonorNans = false;
+      MathErrno = false;
+      AssociativeMath = true;
+      ReciprocalMath = true;
+      SignedZeros = false;
       TrappingMath = false;
+      // If fast-math is set then set the fp-contract mode to fast.
+      FpContract = "fast";
+      break;
+    case options::OPT_fno_fast_math:
+      HonorInfs = true;
+      HonorNans = true;
+      // Turning on -ffast-math (with either flag) removes the need for
+      // MathErrno. However, turning *off* -ffast-math merely restores the
+      // toolchain default (which may be false).
+      MathErrno = getToolChain().IsMathErrnoDefault();
+      AssociativeMath = false;
+      ReciprocalMath = false;
+      SignedZeros = true;
+      TrappingMath = true;
+      // -fno_fast_math restores default denormal and fpcontract handling
+      DenormalFpMath = "";
+      FpContract = "";
+      break;
+    }
+    // If we handled this option claim it
+    A->claim();
+  }
+
+  if (!HonorInfs)
+    CmdArgs.push_back("-menable-no-infs");
+
+  if (!HonorNans)
+    CmdArgs.push_back("-menable-no-nans");
+
+  if (MathErrno)
+    CmdArgs.push_back("-fmath-errno");
+
   if (!MathErrno && AssociativeMath && ReciprocalMath && !SignedZeros &&
       !TrappingMath)
     CmdArgs.push_back("-menable-unsafe-fp-math");
@@ -2406,50 +2437,24 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (!TrappingMath)
     CmdArgs.push_back("-fno-trapping-math");
 
+  if (!DenormalFpMath.empty())
+    CmdArgs.push_back(Args.MakeArgString("-fdenormal-fp-math="+DenormalFpMath));
 
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
-                               options::OPT_fno_fast_math,
-                               options::OPT_funsafe_math_optimizations,
-                               options::OPT_fno_unsafe_math_optimizations,
-                               options::OPT_fdenormal_fp_math_EQ))
-    if (A->getOption().getID() != options::OPT_fno_fast_math &&
-        A->getOption().getID() != options::OPT_fno_unsafe_math_optimizations)
-      Args.AddLastArg(CmdArgs, options::OPT_fdenormal_fp_math_EQ);
-
-  // Validate and pass through -fp-contract option.
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
-                               options::OPT_fno_fast_math,
-                               options::OPT_ffp_contract)) {
-    if (A->getOption().getID() == options::OPT_ffp_contract) {
-      StringRef Val = A->getValue();
-      if (Val == "fast" || Val == "on" || Val == "off") {
-        CmdArgs.push_back(Args.MakeArgString("-ffp-contract=" + Val));
-      } else {
-        D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Val;
-      }
-    } else if (A->getOption().matches(options::OPT_ffast_math) ||
-               (OFastEnabled && A->getOption().matches(options::OPT_Ofast))) {
-      // If fast-math is set then set the fp-contract mode to fast.
-      CmdArgs.push_back(Args.MakeArgString("-ffp-contract=fast"));
-    }
-  }
+  if (!FpContract.empty())
+    CmdArgs.push_back(Args.MakeArgString("-ffp-contract="+FpContract));
 
   ParseMRecip(getToolChain().getDriver(), Args, CmdArgs);
 
-  // We separately look for the '-ffast-math' and '-ffinite-math-only' flags,
-  // and if we find them, tell the frontend to provide the appropriate
-  // preprocessor macros. This is distinct from enabling any optimizations as
-  // these options induce language changes which must survive serialization
-  // and deserialization, etc.
-  if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
-                               options::OPT_fno_fast_math))
-    if (!A->getOption().matches(options::OPT_fno_fast_math))
-      CmdArgs.push_back("-ffast-math");
-  if (Arg *A = Args.getLastArg(options::OPT_ffinite_math_only,
-                               options::OPT_fno_fast_math))
-    if (A->getOption().matches(options::OPT_ffinite_math_only))
-      CmdArgs.push_back("-ffinite-math-only");
+  // -ffast-math enables the __FAST_MATH__ preprocessor macro, but check for the
+  // individual features enabled by -ffast-math instead of the option itself as
+  // that's consistent with gcc's behaviour.
+  if (!HonorInfs && !HonorNans && !MathErrno && AssociativeMath &&
+      ReciprocalMath && !SignedZeros && !TrappingMath)
+    CmdArgs.push_back("-ffast-math");
+
+  // Handle __FINITE_MATH_ONLY__ similarly.
+  if (!HonorInfs && !HonorNans)
+    CmdArgs.push_back("-ffinite-math-only");
 
   // Decide whether to use verbose asm. Verbose assembly is the default on
   // toolchains which have the integrated assembler on by default.

diff --git a/test/Driver/fast-math.c b/test/Driver/fast-math.c
index 025651d0a39502b696bd7c34afccc2e721dfb740..97fda009b9cf239a7e91e839f598dbd8ffb75e7f 100644 (file)
--- a/test/Driver/fast-math.c
+++ b/test/Driver/fast-math.c
@@ -148,20 +148,31 @@
 //
 // One umbrella flag is *really* weird and also changes the semantics of the
 // program by adding a special preprocessor macro. Check that the frontend flag
-// modeling this semantic change is provided. Also check that the semantic
-// impact remains even if every optimization is disabled.
+// modeling this semantic change is provided. Also check that the flag is not
+// present if any of the optimization is disabled.
 // RUN: %clang -### -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // RUN: %clang -### -fno-fast-math -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
-// RUN: %clang -### -ffast-math -fno-finite-math-only \
-// RUN:     -fno-unsafe-math-optimizations -fmath-errno -c %s 2>&1 \
+// RUN: %clang -### -funsafe-math-optimizations -ffinite-math-only \
+// RUN:     -fno-math-errno -ffp-contract=fast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
+// RUN: %clang -### -fno-honor-infinities -fno-honor-nans -fno-math-errno \
+// RUN:     -fassociative-math -freciprocal-math -fno-signed-zeros \
+// RUN:     -fno-trapping-math -ffp-contract=fast -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FAST-MATH %s
 // CHECK-FAST-MATH: "-cc1"
 // CHECK-FAST-MATH: "-ffast-math"
+// CHECK-FAST-MATH: "-ffinite-math-only"
 //
 // RUN: %clang -### -ffast-math -fno-fast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
+// RUN: %clang -### -ffast-math -fno-finite-math-only -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
+// RUN: %clang -### -ffast-math -fno-unsafe-math-optimizations -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
+// RUN: %clang -### -ffast-math -fmath-errno -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH %s
 // CHECK-NO-FAST-MATH: "-cc1"
 // CHECK-NO-FAST-MATH-NOT: "-ffast-math"
 //
@@ -179,6 +190,7 @@
 // RUN:   | FileCheck --check-prefix=CHECK-NO-NO-INFS %s
 // CHECK-NO-NO-INFS: "-cc1"
 // CHECK-NO-NO-INFS-NOT: "-menable-no-infs"
+// CHECK-NO-NO-INFS-NOT: "-ffinite-math-only"
 // CHECK-NO-NO-INFS: "-o"
 //
 // RUN: %clang -### -fno-honor-nans -fhonor-nans -c %s 2>&1 \
@@ -193,6 +205,7 @@
 // RUN:   | FileCheck --check-prefix=CHECK-NO-NO-NANS %s
 // CHECK-NO-NO-NANS: "-cc1"
 // CHECK-NO-NO-NANS-NOT: "-menable-no-nans"
+// CHECK-NO-NO-NANS-NOT: "-ffinite-math-only"
 // CHECK-NO-NO-NANS: "-o"
 //
 // RUN: %clang -### -fassociative-math -freciprocal-math -fno-signed-zeros \