Process the -freciprocal-math optimization flag (PR20912)

The driver currently accepts but ignores the -freciprocal-math flag.
This patch passes the flag through and enables 'arcp' fast-math-flag
generation in IR.

Note that this change does not actually enable the optimization for
any target. The reassociation optimization that this flag specifies
was implemented by http://reviews.llvm.org/D6334 :
http://llvm.org/viewvc/llvm-project?view=revision&revision=222510

Because the optimization is done in the backend rather than IR,
the backend must be modified to understand instruction-level
fast-math-flags or a new function-level attribute must be created.

Also note that -freciprocal-math is independent of any target-specific
usage of reciprocal estimate hardware instructions. That requires
its own flag ('-mrecip').

https://llvm.org/bugs/show_bug.cgi?id=20912

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@234493 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index 4e1afbe4e93213db80870155ac50bded9405bcd5..45729cf0ab624acad0053b4346602244dcee17a8 100644 (file)
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -561,7 +561,9 @@ def fno_unsafe_math_optimizations : Flag<["-"], "fno-unsafe-math-optimizations">
   Group<f_Group>;
 def fassociative_math : Flag<["-"], "fassociative-math">, Group<f_Group>;
 def fno_associative_math : Flag<["-"], "fno-associative-math">, Group<f_Group>;
-def freciprocal_math : Flag<["-"], "freciprocal-math">, Group<f_Group>;
+def freciprocal_math :
+  Flag<["-"], "freciprocal-math">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Allow division operations to be reassociated">;
 def fno_reciprocal_math : Flag<["-"], "fno-reciprocal-math">, Group<f_Group>;
 def ffinite_math_only : Flag<["-"], "ffinite-math-only">, Group<f_Group>, Flags<[CC1Option]>;
 def fno_finite_math_only : Flag<["-"], "fno-finite-math-only">, Group<f_Group>;

diff --git a/include/clang/Frontend/CodeGenOptions.def b/include/clang/Frontend/CodeGenOptions.def
index 514716f361870650ea7204a3ced811a5b75f1108..188171b86e9285437f833bf44cd306d74beae565 100644 (file)
--- a/include/clang/Frontend/CodeGenOptions.def
+++ b/include/clang/Frontend/CodeGenOptions.def
@@ -81,7 +81,8 @@ CODEGENOPT(NoGlobalMerge     , 1, 0) ///< Set when -mno-global-merge is enabled.
 CODEGENOPT(NoImplicitFloat   , 1, 0) ///< Set when -mno-implicit-float is enabled.
 CODEGENOPT(NoInfsFPMath      , 1, 0) ///< Assume FP arguments, results not +-Inf.
 CODEGENOPT(NoSignedZeros     , 1, 0) ///< Allow ignoring the signedness of FP zero
-CODEGENOPT(NoInline          , 1, 0) ///< Set when -fno-inline is enabled. 
+CODEGENOPT(ReciprocalMath    , 1, 0) ///< Allow FP divisions to be reassociated.
+CODEGENOPT(NoInline          , 1, 0) ///< Set when -fno-inline is enabled.
                                      ///< Disables use of the inline keyword.
 CODEGENOPT(NoNaNsFPMath      , 1, 0) ///< Assume FP arguments, results not NaN.
 CODEGENOPT(NoZeroInitializedInBSS , 1, 0) ///< -fno-zero-initialized-in-bss.

diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index e59a50ee76c9818776437a4ddc769929111d23ce..8401d722f42a7f1f205b9830976127ed82f921c2 100644 (file)
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -70,6 +70,9 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm, bool suppressNewContext)
   if (CGM.getCodeGenOpts().NoSignedZeros) {
     FMF.setNoSignedZeros();
   }
+  if (CGM.getCodeGenOpts().ReciprocalMath) {
+    FMF.setAllowReciprocal();
+  }
   Builder.SetFastMathFlags(FMF);
 }
 

diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index f0fc574bd01d97fe575a1eb350a3ab844a460e33..9ebf681aabde39324c80bfb15808928b0a722d49 100644 (file)
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -3062,6 +3062,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (!SignedZeros)
     CmdArgs.push_back("-fno-signed-zeros");
 
+  if (ReciprocalMath)
+    CmdArgs.push_back("-freciprocal-math");
+
   // Validate and pass through -fp-contract option. 
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 5d2cdae6e0092e0f3dea4bf42b357f66bb79b9e3..cd0a7c4640c35d295f619d90d599ef8042799fe3 100644 (file)
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -451,6 +451,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
                        Args.hasArg(OPT_cl_finite_math_only) ||
                        Args.hasArg(OPT_cl_fast_relaxed_math));
   Opts.NoSignedZeros = Args.hasArg(OPT_fno_signed_zeros);
+  Opts.ReciprocalMath = Args.hasArg(OPT_freciprocal_math);
   Opts.NoZeroInitializedInBSS = Args.hasArg(OPT_mno_zero_initialized_in_bss);
   Opts.BackendOptions = Args.getAllArgValues(OPT_backend_option);
   Opts.NumRegisterParameters = getLastArgIntValue(Args, OPT_mregparm, 0, Diags);

diff --git a/test/CodeGen/finite-math.c b/test/CodeGen/finite-math.c
index fd8fcf6fad19601859e7da34a9fae3c097236d2f..8365b56fe56bb7ab2a3436b2d8658d01229da015 100644 (file)
--- a/test/CodeGen/finite-math.c
+++ b/test/CodeGen/finite-math.c
@@ -1,5 +1,6 @@
 // RUN: %clang_cc1 -ffinite-math-only -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=FINITE
 // RUN: %clang_cc1 -fno-signed-zeros -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK  -check-prefix=NSZ
+// RUN: %clang_cc1 -freciprocal-math -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK  -check-prefix=RECIP
 
 float f0, f1, f2;
 
@@ -8,6 +9,7 @@ void foo(void) {
 
   // FINITE: fadd nnan ninf
   // NSZ: fadd nsz
+  // RECIP: fadd arcp
   f0 = f1 + f2;
 
   // CHECK: ret

diff --git a/test/Driver/fast-math.c b/test/Driver/fast-math.c
index bacd7fe4cbb4ddeec0db221367ef30846501ad0d..24c30386da12fffe6cbcccab4a32e2797649f471 100644 (file)
--- a/test/Driver/fast-math.c
+++ b/test/Driver/fast-math.c
@@ -40,6 +40,21 @@
 // CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH: "-cc1"
 // CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH-NOT: "-fno-signed-zeros"
 //
+// RUN: %clang -### -freciprocal-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-RECIPROCAL-MATH %s
+// CHECK-RECIPROCAL-MATH: "-cc1"
+// CHECK-RECIPROCAL-MATH: "-freciprocal-math"
+//
+// RUN: %clang -### -fno-fast-math -freciprocal-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH-RECIPROCAL-MATH %s
+// CHECK-NO-FAST-MATH-RECIPROCAL-MATH: "-cc1"
+// CHECK-NO-FAST-MATH-RECIPROCAL-MATH: "-freciprocal-math"
+//
+// RUN: %clang -### -freciprocal-math -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-RECIPROCAL-MATH-NO-FAST-MATH %s
+// CHECK-RECIPROCAL-MATH-NO-FAST-MATH: "-cc1"
+// CHECK-RECIPROCAL-MATH-NO-FAST-MATH-NOT: "-freciprocal-math"
+//
 // RUN: %clang -### -fno-honor-nans -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-NANS %s
 // CHECK-NO-NANS: "-cc1"