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
llvm-svn: 234493
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 4e1afbe..45729cf 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -561,7 +561,9 @@
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/clang/include/clang/Frontend/CodeGenOptions.def b/clang/include/clang/Frontend/CodeGenOptions.def
index 514716f..188171b 100644
--- a/clang/include/clang/Frontend/CodeGenOptions.def
+++ b/clang/include/clang/Frontend/CodeGenOptions.def
@@ -81,7 +81,8 @@
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/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index e59a50e..8401d72 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -70,6 +70,9 @@
if (CGM.getCodeGenOpts().NoSignedZeros) {
FMF.setNoSignedZeros();
}
+ if (CGM.getCodeGenOpts().ReciprocalMath) {
+ FMF.setAllowReciprocal();
+ }
Builder.SetFastMathFlags(FMF);
}
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index f0fc574..9ebf681 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3062,6 +3062,9 @@
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/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 5d2cdae..cd0a7c4 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -451,6 +451,7 @@
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/clang/test/CodeGen/finite-math.c b/clang/test/CodeGen/finite-math.c
index fd8fcf6..8365b56 100644
--- a/clang/test/CodeGen/finite-math.c
+++ b/clang/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 @@
// FINITE: fadd nnan ninf
// NSZ: fadd nsz
+ // RECIP: fadd arcp
f0 = f1 + f2;
// CHECK: ret
diff --git a/clang/test/Driver/fast-math.c b/clang/test/Driver/fast-math.c
index bacd7fe..24c3038 100644
--- a/clang/test/Driver/fast-math.c
+++ b/clang/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"