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.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194967 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/BackendUtil.cpp b/lib/CodeGen/BackendUtil.cpp
index e159a7a..90b0f68 100644
--- a/lib/CodeGen/BackendUtil.cpp
+++ b/lib/CodeGen/BackendUtil.cpp
@@ -242,6 +242,7 @@
PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
+ PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
if (!CodeGenOpts.SampleProfileFile.empty())
PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,