mamai created this revision.
mamai added a reviewer: chandlerc.
mamai added a subscriber: cfe-commits.
mamai set the repository for this revision to rL LLVM.
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);
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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