[CodeGen] Generate follow-up metadata for loops with more than one transformation.

Before this patch, CGLoop would dump all transformations for a loop into
a single LoopID without encoding any order in which to apply them.
rL348944 added the possibility to encode a transformation order using
followup-attributes.

When a loop has more than one transformation, use the follow-up
attribute define the order in which they are applied. The emitted order
is the defacto order as defined by the current LLVM pass pipeline,
which is:

  LoopFullUnrollPass
  LoopDistributePass
  LoopVectorizePass
  LoopUnrollAndJamPass
  LoopUnrollPass
  MachinePipeliner

This patch should therefore not change the assembly output, assuming
that all explicit transformations can be applied, and no implicit
transformations in-between. In the former case,
WarnMissedTransformationsPass should emit a warning (except for
MachinePipeliner which is not implemented yet). The latter could be
avoided by adding 'llvm.loop.disable_nonforced' attributes.

Because LoopUnrollAndJamPass processes a loop nest, generation of the
MDNode is delayed to after the inner loop metadata have been processed.
A temporary LoopID is therefore used to annotate instructions and
RAUW'ed by the actual LoopID later.

Differential Revision: https://reviews.llvm.org/D57978

llvm-svn: 357415

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/test/CodeGenCXX/pragma-loop-safety-outer.cpp b/clang/test/CodeGenCXX/pragma-loop-safety-outer.cpp
index d99b86ffe23..670cb29edd4 100644
--- a/clang/test/CodeGenCXX/pragma-loop-safety-outer.cpp
+++ b/clang/test/CodeGenCXX/pragma-loop-safety-outer.cpp
@@ -18,5 +18,5 @@ void vectorize_outer_test(int *List, int Length) {
 
 // CHECK: ![[ACCESS_GROUP_2]] = distinct !{}
 // CHECK: ![[INNER_LOOPID]] = distinct !{![[INNER_LOOPID]],
-// CHECK: ![[OUTER_LOOPID]] = distinct !{![[OUTER_LOOPID]], {{.*}} ![[PARALLEL_ACCESSES_9:[0-9]+]]}
+// CHECK: ![[OUTER_LOOPID]] = distinct !{![[OUTER_LOOPID]], ![[PARALLEL_ACCESSES_9:[0-9]+]]
 // CHECK: ![[PARALLEL_ACCESSES_9]] = !{!"llvm.loop.parallel_accesses", ![[ACCESS_GROUP_2]]}