From b69557ed6f6d5063705e60f771a612aa62ec6b22 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Sat, 18 May 2013 20:47:36 +0000
Subject: [PATCH] Fix a logic bug in the handling of -fmath-errno in the
 driver. We would imply -fno-math-errno if the user passed -fno-fast-math OR
 -ffast-math, regardless of in which order and regardless of the tool chain
 default.

I've fixed this to follow the logic:

1) If the last dominating flag is -fno-math-errno, -ffast-math, or
   -Ofast, then do not use math-errno.
2) If the last dominating flag is an explicit -fmath-errno, do use
   math-errno.
3) Otherwise, use the toolchain default.

This, for example, allows the flag sequence
'-ffast-math ... -fno-fast-math' with no mention of '-fmath-errno' or
'-fno-math-errno' to preserve the toolchain default. Most notably, this
should prevent users trying to disable fast-math optimizations on Darwin
and BSD platforms from simultaneously enabling (pointless) -fmath-errno.

I've enhanced the tests (after more reorganization) to cover this and
other weird permutations of flags and targets.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182203 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Driver/Tools.cpp    | 13 +++++++++++--
 test/Driver/fast-math.c | 34 ++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 4fbc910837..ceb5e3a61e 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2208,8 +2208,17 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math, FastMathAliasOption,
                                options::OPT_fno_fast_math,
                                options::OPT_fmath_errno,
-                               options::OPT_fno_math_errno))
-    MathErrno = A->getOption().getID() == 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");
 
diff --git a/test/Driver/fast-math.c b/test/Driver/fast-math.c
index b69750ae5b..eba25c8fe8 100644
--- a/test/Driver/fast-math.c
+++ b/test/Driver/fast-math.c
@@ -39,17 +39,17 @@
 //
 // RUN: %clang -### -fmath-errno -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
-// RUN: %clang -### -target x86_64-unknown-linux -c %s 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
-// RUN: %clang -### -fmath-errno -fno-fast-math -c %s 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
-// RUN: %clang -### -fno-fast-math -fmath-errno -c %s 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
 // CHECK-MATH-ERRNO: "-cc1"
 // CHECK-MATH-ERRNO: "-fmath-errno"
 //
 // RUN: %clang -### -fmath-errno -fno-math-errno -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
+// CHECK-NO-MATH-ERRNO: "-cc1"
+// CHECK-NO-MATH-ERRNO-NOT: "-fmath-errno"
+//
+// Target defaults for -fmath-errno (reusing the above checks).
+// RUN: %clang -### -target i686-unknown-linux -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
 // RUN: %clang -### -target i686-apple-darwin -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -target x86_64-unknown-freebsd -c %s 2>&1 \
@@ -60,8 +60,26 @@
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 // RUN: %clang -### -target x86_64-unknown-dragonfly -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
-// CHECK-NO-MATH-ERRNO: "-cc1"
-// CHECK-NO-MATH-ERRNO-NOT: "-fmath-errno"
+//
+// Check that -ffast-math disables -fmath-errno, and -fno-fast-math merely
+// preserves the target default. Also check various flag set operations between
+// the two flags. (Resuses above checks.)
+// RUN: %clang -### -ffast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
+// RUN: %clang -### -fmath-errno -ffast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
+// RUN: %clang -### -ffast-math -fmath-errno -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
+// RUN: %clang -### -target i686-unknown-linux -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
+// RUN: %clang -### -target i686-unknown-linux -fno-math-errno -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MATH-ERRNO %s
+// RUN: %clang -### -target i686-apple-darwin -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
+// RUN: %clang -### -target i686-apple-darwin -fno-math-errno -fno-fast-math -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
+// RUN: %clang -### -fno-fast-math -fno-math-errno -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-MATH-ERRNO %s
 //
 // RUN: %clang -### -fno-math-errno -fassociative-math -freciprocal-math \
 // RUN:     -fno-signed-zeros -fno-trapping-math -c %s 2>&1 \
-- 
2.40.0