[PATCH] D19827: Do not disable completely loop unroll according to optimization level.

[Marianne Mailhot-Sarrasin via cfe-commits]

mamai created this revision.
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By disabling completely the loop unroll at some optimization levels (e.g. /Os), the #pragma unroll have no effect at those optimization levels.

This contradicts the paragraph in an llvm blog post about the loop pragmas (http://blog.llvm.org/2014/11/loop-vectorization-diagnostics-and.html) saying the following:

> For example, when compiling for size (-Os) it's a good idea to vectorize the hot loops of the application to improve performance. Vectorization, interleaving, and unrolling can be explicitly specified using the #pragma clang loop directive prior to any for, while, do-while, or c++11 range-based for loop.

Also, as explained in a previous commit, the  loop unroll pass already have the logic to unroll loop are not according to optimization level (http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20130805/085399.html).

Repository:
  rL LLVM

http://reviews.llvm.org/D19827

Files:
  lib/Frontend/CompilerInvocation.cpp

Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -511,9 +511,7 @@
                             Args.hasArg(OPT_ffreestanding));
   if (Opts.SimplifyLibCalls)
     getAllNoBuiltinFuncValues(Args, Opts.NoBuiltinFuncs);
-  Opts.UnrollLoops =
-      Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops,
-                   (Opts.OptimizationLevel > 1 && !Opts.OptimizeSize));
+  Opts.UnrollLoops = Args.hasFlag(OPT_funroll_loops, OPT_fno_unroll_loops);
   Opts.RerollLoops = Args.hasArg(OPT_freroll_loops);
 
   Opts.DisableIntegratedAS = Args.hasArg(OPT_fno_integrated_as);


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