r283685 - When optimizing for size, enable loop rerolling by default

[Hal Finkel via cfe-commits]

Author: hfinkel
Date: Sat Oct  8 22:06:31 2016
New Revision: 283685

URL: http://llvm.org/viewvc/llvm-project?rev=283685&view=rev
Log:
When optimizing for size, enable loop rerolling by default

We have a loop-rerolling optimization which can be enabled by using
-freroll-loops. While sometimes loops are hand-unrolled for performance
reasons, when optimizing for size, we should always undo this manual
optimization to produce smaller code (our optimizer's unroller will still
unroll the rerolled loops if it thinks that is a good idea).

Modified:
    cfe/trunk/lib/Driver/Tools.cpp
    cfe/trunk/test/Driver/clang_f_opts.c

Modified: cfe/trunk/lib/Driver/Tools.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=283685&r1=283684&r2=283685&view=diff
==============================================================================
--- cfe/trunk/lib/Driver/Tools.cpp (original)
+++ cfe/trunk/lib/Driver/Tools.cpp Sat Oct  8 22:06:31 2016
@@ -5227,9 +5227,18 @@ void Clang::ConstructJob(Compilation &C,
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_freroll_loops,
-                               options::OPT_fno_reroll_loops))
+                               options::OPT_fno_reroll_loops)) {
     if (A->getOption().matches(options::OPT_freroll_loops))
       CmdArgs.push_back("-freroll-loops");
+  } else if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
+    // If rerolling is not explicitly enabled or disabled, then enable when
+    // optimizing for size.
+    if (A->getOption().matches(options::OPT_O)) {
+      StringRef S(A->getValue());
+      if (S == "s" || S == "z")
+        CmdArgs.push_back("-freroll-loops");
+    }
+  }
 
   Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
   Args.AddLastArg(CmdArgs, options::OPT_funroll_loops,

Modified: cfe/trunk/test/Driver/clang_f_opts.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/clang_f_opts.c?rev=283685&r1=283684&r2=283685&view=diff
==============================================================================
--- cfe/trunk/test/Driver/clang_f_opts.c (original)
+++ cfe/trunk/test/Driver/clang_f_opts.c Sat Oct  8 22:06:31 2016
@@ -47,7 +47,12 @@
 // CHECK-NO-UNROLL-LOOPS: "-fno-unroll-loops"
 
 // RUN: %clang -### -S -freroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-REROLL-LOOPS %s
+// RUN: %clang -### -S -Os %s 2>&1 | FileCheck -check-prefix=CHECK-REROLL-LOOPS %s
+// RUN: %clang -### -S -Oz %s 2>&1 | FileCheck -check-prefix=CHECK-REROLL-LOOPS %s
 // RUN: %clang -### -S -fno-reroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-NO-REROLL-LOOPS %s
+// RUN: %clang -### -S -Os -fno-reroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-NO-REROLL-LOOPS %s
+// RUN: %clang -### -S -Oz -fno-reroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-NO-REROLL-LOOPS %s
+// RUN: %clang -### -S -O1 %s 2>&1 | FileCheck -check-prefix=CHECK-NO-REROLL-LOOPS %s
 // RUN: %clang -### -S -fno-reroll-loops -freroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-REROLL-LOOPS %s
 // RUN: %clang -### -S -freroll-loops -fno-reroll-loops %s 2>&1 | FileCheck -check-prefix=CHECK-NO-REROLL-LOOPS %s
 // CHECK-REROLL-LOOPS: "-freroll-loops"