Add llvm.licm.disable metadata

For some targets the LICM pass can result in sub-optimal code in some
cases where it would be better not to run the pass, but it isn't
always possible to suppress the transformations heuristically.

Where the front-end has insight into such cases it is beneficial
to attach loop metadata to disable the pass - this change adds the
llvm.licm.disable metadata to enable that.

Differential Revision: https://reviews.llvm.org/D64557

llvm-svn: 368296

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index ce296b9d4dd..4c6c2edc385 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -45,6 +45,7 @@ using namespace llvm::PatternMatch;
 #define DEBUG_TYPE "loop-utils"
 
 static const char *LLVMLoopDisableNonforced = "llvm.loop.disable_nonforced";
+static const char *LLVMLoopDisableLICM = "llvm.licm.disable";
 
 bool llvm::formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
                                    MemorySSAUpdater *MSSAU,
@@ -379,6 +380,10 @@ bool llvm::hasDisableAllTransformsHint(const Loop *L) {
   return getBooleanLoopAttribute(L, LLVMLoopDisableNonforced);
 }
 
+bool llvm::hasDisableLICMTransformsHint(const Loop *L) {
+  return getBooleanLoopAttribute(L, LLVMLoopDisableLICM);
+}
+
 TransformationMode llvm::hasUnrollTransformation(Loop *L) {
   if (getBooleanLoopAttribute(L, "llvm.loop.unroll.disable"))
     return TM_SuppressedByUser;