[PATCH] D89378: [LoopFlatten] Loop limit invariant checks

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer created this revision.
SjoerdMeijer added reviewers: ostannard, dmgreen, fhahn.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.
SjoerdMeijer requested review of this revision.

If the loop limit is not invariant don't directly bail out, but try to make it invariant with makeLoopInvariant.
I precommitted the test case for this in rG20c7ab87a78c <https://reviews.llvm.org/rG20c7ab87a78c8d808a7d1e662d5bfd580dcdc12e>.


https://reviews.llvm.org/D89378

Files:
  llvm/lib/Transforms/Scalar/LoopFlatten.cpp
  llvm/test/Transforms/LoopFlatten/limit-not-invariant.ll


Index: llvm/test/Transforms/LoopFlatten/limit-not-invariant.ll
===================================================================
--- llvm/test/Transforms/LoopFlatten/limit-not-invariant.ll
+++ llvm/test/Transforms/LoopFlatten/limit-not-invariant.ll
@@ -11,11 +11,11 @@
 ; CHECK-NEXT:    br i1 [[CMP26_NOT]], label [[FOR_END12:%.*]], label [[FOR_COND1_PREHEADER_LR_PH:%.*]]
 ; CHECK:       for.cond1.preheader.lr.ph:
 ; CHECK-NEXT:    [[CONV4:%.*]] = sext i16 [[VAL:%.*]] to i32
+; CHECK-NEXT:    [[WIDE_TRIP_COUNT:%.*]] = zext i32 [[N]] to i64
 ; CHECK-NEXT:    br label [[FOR_COND1_PREHEADER_US:%.*]]
 ; CHECK:       for.cond1.preheader.us:
 ; CHECK-NEXT:    [[I_027_US:%.*]] = phi i32 [ 0, [[FOR_COND1_PREHEADER_LR_PH]] ], [ [[INC11_US:%.*]], [[FOR_COND1_FOR_INC10_CRIT_EDGE_US:%.*]] ]
 ; CHECK-NEXT:    [[MUL_US:%.*]] = mul i32 [[I_027_US]], [[N]]
-; CHECK-NEXT:    [[WIDE_TRIP_COUNT:%.*]] = zext i32 [[N]] to i64
 ; CHECK-NEXT:    br label [[FOR_BODY3_US:%.*]]
 ; CHECK:       for.body3.us:
 ; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ 0, [[FOR_COND1_PREHEADER_US]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY3_US]] ]
@@ -88,11 +88,11 @@
 ; CHECK-NEXT:    br i1 [[CMP26_NOT]], label [[FOR_END12:%.*]], label [[FOR_COND1_PREHEADER_LR_PH:%.*]]
 ; CHECK:       for.cond1.preheader.lr.ph:
 ; CHECK-NEXT:    [[CONV4:%.*]] = sext i16 [[VAL:%.*]] to i32
+; CHECK-NEXT:    [[TRUNC_TRIP_COUNT:%.*]] = trunc i64 [[M:%.*]] to i32
 ; CHECK-NEXT:    br label [[FOR_COND1_PREHEADER_US:%.*]]
 ; CHECK:       for.cond1.preheader.us:
 ; CHECK-NEXT:    [[I_027_US:%.*]] = phi i32 [ 0, [[FOR_COND1_PREHEADER_LR_PH]] ], [ [[INC11_US:%.*]], [[FOR_COND1_FOR_INC10_CRIT_EDGE_US:%.*]] ]
 ; CHECK-NEXT:    [[MUL_US:%.*]] = mul i32 [[I_027_US]], [[N]]
-; CHECK-NEXT:    [[TRUNC_TRIP_COUNT:%.*]] = trunc i64 [[M:%.*]] to i32
 ; CHECK-NEXT:    br label [[FOR_BODY3_US:%.*]]
 ; CHECK:       for.body3.us:
 ; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ 0, [[FOR_COND1_PREHEADER_US]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY3_US]] ]
Index: llvm/lib/Transforms/Scalar/LoopFlatten.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopFlatten.cpp
+++ llvm/lib/Transforms/Scalar/LoopFlatten.cpp
@@ -429,11 +429,12 @@
 
   // Both of the loop limit values must be invariant in the outer loop
   // (non-instructions are all inherently invariant).
-  if (!OuterLoop->isLoopInvariant(InnerLimit)) {
+  bool Changed;
+  if (!OuterLoop->makeLoopInvariant(InnerLimit, Changed)) {
     LLVM_DEBUG(dbgs() << "inner loop limit not invariant\n");
     return false;
   }
-  if (!OuterLoop->isLoopInvariant(OuterLimit)) {
+  if (!OuterLoop->makeLoopInvariant(OuterLimit, Changed)) {
     LLVM_DEBUG(dbgs() << "outer loop limit not invariant\n");
     return false;
   }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D89378.298087.patch
Type: text/x-patch
Size: 2787 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20201014/3ea0099f/attachment.bin>