[PATCH] process the -fno-signed-zeros optimization flag (PR20870)

[Sanjay Patel]

Hi hfinkel, majnemer, chandlerc,

The driver currently accepts but ignores the -fno-signed-zeros flag. This patch passes the flag through and enables 'nsz' fast-math-flag generation in IR.

This should resolve bug 20870 ( http://llvm.org/bugs/show_bug.cgi?id=20870 ); patches for the optimizer were checked in at:
http://llvm.org/viewvc/llvm-project?view=revision&revision=225050
http://llvm.org/viewvc/llvm-project?view=revision&revision=224583

http://reviews.llvm.org/D6873

Files:
  include/clang/Driver/Options.td
  lib/Driver/Tools.cpp
  lib/Frontend/CompilerInvocation.cpp
  test/CodeGen/finite-math.c
  test/Driver/fast-math.c

Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -556,7 +556,9 @@
 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>;
 def fsigned_zeros : Flag<["-"], "fsigned-zeros">, Group<f_Group>;
-def fno_signed_zeros : Flag<["-"], "fno-signed-zeros">, Group<f_Group>;
+def fno_signed_zeros :
+  Flag<["-"], "fno-signed-zeros">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Allow optimizations that ignore the sign of floating point zeros">;
 def fhonor_nans : Flag<["-"], "fhonor-nans">, Group<f_Group>;
 def fno_honor_nans : Flag<["-"], "fno-honor-nans">, Group<f_Group>;
 def fhonor_infinities : Flag<["-"], "fhonor-infinities">, Group<f_Group>;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -2942,6 +2942,8 @@
       !TrappingMath)
     CmdArgs.push_back("-menable-unsafe-fp-math");
 
+  if (!SignedZeros)
+    CmdArgs.push_back("-fno-signed-zeros");
 
   // Validate and pass through -fp-contract option. 
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -426,7 +426,8 @@
                        Args.hasArg(OPT_cl_unsafe_math_optimizations) ||
                        Args.hasArg(OPT_cl_finite_math_only) ||
                        Args.hasArg(OPT_cl_fast_relaxed_math));
-  Opts.NoSignedZeros = Args.hasArg(OPT_cl_no_signed_zeros);
+  Opts.NoSignedZeros = (Args.hasArg(OPT_cl_no_signed_zeros) ||
+                        Args.hasArg(OPT_fno_signed_zeros));
   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);
Index: test/CodeGen/finite-math.c
===================================================================
--- test/CodeGen/finite-math.c
+++ test/CodeGen/finite-math.c
@@ -1,11 +1,15 @@
-// RUN: %clang_cc1 -ffinite-math-only -emit-llvm -o - %s | FileCheck %s
+// 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
+
 float f0, f1, f2;
 
 void foo(void) {
   // CHECK-LABEL: define void @foo()
 
-  // CHECK: fadd nnan ninf
+  // FINITE: fadd nnan ninf
+  // NSZ: fadd nsz
   f0 = f1 + f2;
 
   // CHECK: ret
 }
+
Index: test/Driver/fast-math.c
===================================================================
--- test/Driver/fast-math.c
+++ test/Driver/fast-math.c
@@ -25,6 +25,21 @@
 // CHECK-NO-INFS-NO-FAST-MATH: "-cc1"
 // CHECK-NO-INFS-NO-FAST-MATH-NOT: "-menable-no-infs"
 //
+// RUN: %clang -### -fno-signed-zeros -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-SIGNED-ZEROS %s
+// CHECK-NO-SIGNED-ZEROS: "-cc1"
+// CHECK-NO-SIGNED-ZEROS: "-fno-signed-zeros"
+//
+// RUN: %clang -### -fno-fast-math -fno-signed-zeros -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-FAST-MATH-NO-SIGNED-ZEROS %s
+// CHECK-NO-FAST-MATH-NO-SIGNED-ZEROS: "-cc1"
+// CHECK-NO-FAST-MATH-NO-SIGNED-ZEROS: "-fno-signed-zeros"
+//
+// RUN: %clang -### -fno-signed-zeros -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH %s
+// CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH: "-cc1"
+// CHECK-NO-SIGNED-ZEROS-NO-FAST-MATH-NOT: "-fno-signed-zeros"
+//
 // RUN: %clang -### -fno-honor-nans -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-NANS %s
 // CHECK-NO-NANS: "-cc1"

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