r194967 - Add -freroll-loops to enable loop rerolling

[Hal Finkel]

Author: hfinkel
Date: Sun Nov 17 10:03:29 2013
New Revision: 194967

URL: http://llvm.org/viewvc/llvm-project?rev=194967&view=rev
Log:
Add -freroll-loops to enable loop rerolling

This adds -freroll-loops (and -fno-reroll-loops in the usual way) to enable
loop rerolling as part of the optimization pass manager. This transformation
can enable vectorization, reduce code size (or both).

Briefly, loop rerolling can transform a loop like this:

for (int i = 0; i < 3200; i += 5) {
  a[i]     += alpha * b[i];
  a[i + 1] += alpha * b[i + 1];
  a[i + 2] += alpha * b[i + 2];
  a[i + 3] += alpha * b[i + 3];
  a[i + 4] += alpha * b[i + 4];
}

into this:

for (int i = 0; i < 3200; ++i) {
  a[i] += alpha * b[i];
}

Loop rerolling is currently disabled by default at all optimization levels.

Modified:
    cfe/trunk/include/clang/Driver/Options.td
    cfe/trunk/include/clang/Frontend/CodeGenOptions.def
    cfe/trunk/lib/CodeGen/BackendUtil.cpp
    cfe/trunk/lib/Driver/Tools.cpp
    cfe/trunk/lib/Frontend/CompilerInvocation.cpp
    cfe/trunk/test/Driver/clang_f_opts.c

Modified: cfe/trunk/include/clang/Driver/Options.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/Options.td?rev=194967&r1=194966&r2=194967&view=diff
==============================================================================
--- cfe/trunk/include/clang/Driver/Options.td (original)
+++ cfe/trunk/include/clang/Driver/Options.td Sun Nov 17 10:03:29 2013
@@ -828,6 +828,10 @@ def funroll_loops : Flag<["-"], "funroll
   HelpText<"Turn on loop unroller">, Flags<[CC1Option]>;
 def fno_unroll_loops : Flag<["-"], "fno-unroll-loops">, Group<f_Group>,
   HelpText<"Turn off loop unroller">, Flags<[CC1Option]>;
+def freroll_loops : Flag<["-"], "freroll-loops">, Group<f_Group>,
+  HelpText<"Turn on loop reroller">, Flags<[CC1Option]>;
+def fno_reroll_loops : Flag<["-"], "fno-reroll-loops">, Group<f_Group>,
+  HelpText<"Turn off loop reroller">;
 def funsigned_bitfields : Flag<["-"], "funsigned-bitfields">, Group<f_Group>;
 def funsigned_char : Flag<["-"], "funsigned-char">, Group<f_Group>;
 def fno_unsigned_char : Flag<["-"], "fno-unsigned-char">, Group<clang_ignored_f_Group>;

Modified: cfe/trunk/include/clang/Frontend/CodeGenOptions.def
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Frontend/CodeGenOptions.def?rev=194967&r1=194966&r2=194967&view=diff
==============================================================================
--- cfe/trunk/include/clang/Frontend/CodeGenOptions.def (original)
+++ cfe/trunk/include/clang/Frontend/CodeGenOptions.def Sun Nov 17 10:03:29 2013
@@ -107,6 +107,7 @@ CODEGENOPT(TimePasses        , 1, 0) ///
 CODEGENOPT(UnitAtATime       , 1, 1) ///< Unused. For mirroring GCC optimization
                                      ///< selection.
 CODEGENOPT(UnrollLoops       , 1, 0) ///< Control whether loops are unrolled.
+CODEGENOPT(RerollLoops       , 1, 0) ///< Control whether loops are rerolled.
 CODEGENOPT(UnsafeFPMath      , 1, 0) ///< Allow unsafe floating point optzns.
 CODEGENOPT(UnwindTables      , 1, 0) ///< Emit unwind tables.
 CODEGENOPT(VectorizeBB       , 1, 0) ///< Run basic block vectorizer.

Modified: cfe/trunk/lib/CodeGen/BackendUtil.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/BackendUtil.cpp?rev=194967&r1=194966&r2=194967&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/BackendUtil.cpp (original)
+++ cfe/trunk/lib/CodeGen/BackendUtil.cpp Sun Nov 17 10:03:29 2013
@@ -242,6 +242,7 @@ void EmitAssemblyHelper::CreatePasses(Ta
 
   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
+  PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
 
   if (!CodeGenOpts.SampleProfileFile.empty())
     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,

Modified: cfe/trunk/lib/Driver/Tools.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=194967&r1=194966&r2=194967&view=diff
==============================================================================
--- cfe/trunk/lib/Driver/Tools.cpp (original)
+++ cfe/trunk/lib/Driver/Tools.cpp Sun Nov 17 10:03:29 2013
@@ -3058,6 +3058,12 @@ void Clang::ConstructJob(Compilation &C,
     if (A->getOption().matches(options::OPT_fno_strict_overflow))
       CmdArgs.push_back("-fwrapv");
   }
+
+  if (Arg *A = Args.getLastArg(options::OPT_freroll_loops,
+                               options::OPT_fno_reroll_loops))
+    if (A->getOption().matches(options::OPT_freroll_loops))
+      CmdArgs.push_back("-freroll-loops");
+
   Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
   Args.AddLastArg(CmdArgs, options::OPT_funroll_loops,
                   options::OPT_fno_unroll_loops);

Modified: cfe/trunk/lib/Frontend/CompilerInvocation.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Frontend/CompilerInvocation.cpp?rev=194967&r1=194966&r2=194967&view=diff
==============================================================================
--- cfe/trunk/lib/Frontend/CompilerInvocation.cpp (original)
+++ cfe/trunk/lib/Frontend/CompilerInvocation.cpp Sun Nov 17 10:03:29 2013
@@ -355,6 +355,7 @@ static bool ParseCodeGenArgs(CodeGenOpti
   Opts.UnrollLoops =
       Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops,
                    (Opts.OptimizationLevel > 1 && !Opts.OptimizeSize));
+  Opts.RerollLoops = Args.hasArg(OPT_freroll_loops);
 
   Opts.Autolink = !Args.hasArg(OPT_fno_autolink);
   Opts.SampleProfileFile = Args.getLastArgValue(OPT_fprofile_sample_use_EQ);

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=194967&r1=194966&r2=194967&view=diff
==============================================================================
--- cfe/trunk/test/Driver/clang_f_opts.c (original)
+++ cfe/trunk/test/Driver/clang_f_opts.c Sun Nov 17 10:03:29 2013
@@ -44,6 +44,13 @@
 // CHECK-UNROLL-LOOPS: "-funroll-loops"
 // 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 -fno-reroll-loops %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"
+// CHECK-NO-REROLL-LOOPS-NOT: "-freroll-loops"
+
 // RUN: %clang -### -S -fprofile-sample-use=%S/Inputs/file.prof %s 2>&1 | FileCheck -check-prefix=CHECK-SAMPLE-PROFILE %s
 // CHECK-SAMPLE-PROFILE: "-fprofile-sample-use={{.*}}/file.prof"