[OpenMPIRBuilder] Fix tripcount not a multiple of tile size (llvm#154999)

The emitted code tests whether the current tile should executing the
remainder iterations by checking the logical iteration number is the one
after the floor iterations that execute the non-remainder iterations.
There are two counts of how many iterations there are: Those of
non-remainder iterations (simply rounded-down division of tripcount and
tile size), and those including an additional floor iteration for the
remainder iterations. The code was used the wrong one that caused the
condition to never match.

Author: Meinersbur

clang/test/OpenMP/irbuilder_unroll_partial_factor_for.c

@@ -79,7 +79,7 @@ void unroll_partial_heuristic_for(int n, float *a, float *b, float *c, float *d)
 // CHECK-NEXT:    br i1 [[OMP_FLOOR0_CMP]], label [[OMP_FLOOR0_BODY:%.*]], label [[OMP_FLOOR0_EXIT:%.*]]
 // CHECK:       omp_floor0.body:
 // CHECK-NEXT:    [[TMP13:%.*]] = add i32 [[OMP_FLOOR0_IV]], [[TMP9]]
-// CHECK-NEXT:    [[TMP14:%.*]] = icmp eq i32 [[TMP13]], [[OMP_FLOOR0_TRIPCOUNT]]
+// CHECK-NEXT:    [[TMP14:%.*]] = icmp eq i32 [[TMP13]], [[TMP4]]
 // CHECK-NEXT:    [[TMP15:%.*]] = select i1 [[TMP14]], i32 [[TMP5]], i32 13
 // CHECK-NEXT:    br label [[OMP_TILE0_PREHEADER:%.*]]
 // CHECK:       omp_tile0.preheader:

clang/test/OpenMP/irbuilder_unroll_partial_heuristic_constant_for.c

@@ -85,7 +85,7 @@ void unroll_partial_heuristic_constant_for(float *a, float *b, float *c, float *
 // CHECK-NEXT:    br i1 [[OMP_FLOOR0_CMP]], label [[OMP_FLOOR0_BODY:%.*]], label [[OMP_FLOOR0_EXIT:%.*]]
 // CHECK:       omp_floor0.body:
 // CHECK-NEXT:    [[TMP12:%.*]] = add i32 [[OMP_FLOOR0_IV]], [[TMP8]]
-// CHECK-NEXT:    [[TMP13:%.*]] = icmp eq i32 [[TMP12]], [[OMP_FLOOR0_TRIPCOUNT]]
+// CHECK-NEXT:    [[TMP13:%.*]] = icmp eq i32 [[TMP12]], [[TMP3]]
 // CHECK-NEXT:    [[TMP14:%.*]] = select i1 [[TMP13]], i32 [[TMP4]], i32 4
 // CHECK-NEXT:    br label [[OMP_TILE0_PREHEADER:%.*]]
 // CHECK:       omp_tile0.preheader:

clang/test/OpenMP/irbuilder_unroll_partial_heuristic_runtime_for.c

@@ -87,7 +87,7 @@ void unroll_partial_heuristic_runtime_for(int n, float *a, float *b, float *c, f
 // CHECK-NEXT:    br i1 [[OMP_FLOOR0_CMP]], label [[OMP_FLOOR0_BODY:%.*]], label [[OMP_FLOOR0_EXIT:%.*]]
 // CHECK:       omp_floor0.body:
 // CHECK-NEXT:    [[TMP13:%.*]] = add i32 [[OMP_FLOOR0_IV]], [[TMP9]]
-// CHECK-NEXT:    [[TMP14:%.*]] = icmp eq i32 [[TMP13]], [[OMP_FLOOR0_TRIPCOUNT]]
+// CHECK-NEXT:    [[TMP14:%.*]] = icmp eq i32 [[TMP13]], [[TMP4]]
 // CHECK-NEXT:    [[TMP15:%.*]] = select i1 [[TMP14]], i32 [[TMP5]], i32 4
 // CHECK-NEXT:    br label [[OMP_TILE0_PREHEADER:%.*]]
 // CHECK:       omp_tile0.preheader:

clang/test/OpenMP/irbuilder_unroll_unroll_partial_factor.c

@@ -75,7 +75,7 @@ void unroll_partial_factor_for(float *a, float *b, float *c, float *d) {
 // CHECK-NEXT:    br i1 [[OMP_FLOOR0_CMP]], label [[OMP_FLOOR0_BODY:%.*]], label [[OMP_FLOOR0_EXIT:%.*]]
 // CHECK:       omp_floor0.body:
 // CHECK-NEXT:    [[TMP12:%.*]] = add i32 [[OMP_FLOOR0_IV]], [[TMP8]]
-// CHECK-NEXT:    [[TMP13:%.*]] = icmp eq i32 [[TMP12]], [[OMP_FLOOR0_TRIPCOUNT]]
+// CHECK-NEXT:    [[TMP13:%.*]] = icmp eq i32 [[TMP12]], [[TMP3]]
 // CHECK-NEXT:    [[TMP14:%.*]] = select i1 [[TMP13]], i32 [[TMP4]], i32 2
 // CHECK-NEXT:    br label [[OMP_TILE0_PREHEADER:%.*]]
 // CHECK:       omp_tile0.preheader:

clang/test/OpenMP/irbuilder_unroll_unroll_partial_heuristic.c

@@ -59,7 +59,7 @@ void unroll_unroll_partial_heuristic(float *a, float *b, float *c, float *d) {
 // CHECK-NEXT:    [[OMP_FLOOR0_CMP:%.*]] = icmp ult i32 [[OMP_FLOOR0_IV]], [[OMP_FLOOR0_TRIPCOUNT]]
 // CHECK-NEXT:    br i1 [[OMP_FLOOR0_CMP]], label [[OMP_FLOOR0_BODY:%.*]], label [[OMP_FLOOR0_EXIT:%.*]]
 // CHECK:       omp_floor0.body:
-// CHECK-NEXT:    [[TMP7:%.*]] = icmp eq i32 [[OMP_FLOOR0_IV]], [[OMP_FLOOR0_TRIPCOUNT]]
+// CHECK-NEXT:    [[TMP7:%.*]] = icmp eq i32 [[OMP_FLOOR0_IV]], [[TMP3]]
 // CHECK-NEXT:    [[TMP8:%.*]] = select i1 [[TMP7]], i32 [[TMP4]], i32 8
 // CHECK-NEXT:    br label [[OMP_TILE0_PREHEADER:%.*]]
 // CHECK:       omp_tile0.preheader:

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -5581,13 +5581,13 @@ OpenMPIRBuilder::tileLoops(DebugLoc DL, ArrayRef<CanonicalLoopInfo *> Loops,
   // Compute the trip counts of the floor loops.
   Builder.SetCurrentDebugLocation(DL);
   Builder.restoreIP(OutermostLoop->getPreheaderIP());
-  SmallVector<Value *, 4> FloorCount, FloorRems;
+  SmallVector<Value *, 4> FloorCompleteCount, FloorCount, FloorRems;
   for (int i = 0; i < NumLoops; ++i) {
     Value *TileSize = TileSizes[i];
     Value *OrigTripCount = OrigTripCounts[i];
     Type *IVType = OrigTripCount->getType();
 
-    Value *FloorTripCount = Builder.CreateUDiv(OrigTripCount, TileSize);
+    Value *FloorCompleteTripCount = Builder.CreateUDiv(OrigTripCount, TileSize);
     Value *FloorTripRem = Builder.CreateURem(OrigTripCount, TileSize);
 
     // 0 if tripcount divides the tilesize, 1 otherwise.
@@ -5601,11 +5601,12 @@ OpenMPIRBuilder::tileLoops(DebugLoc DL, ArrayRef<CanonicalLoopInfo *> Loops,
         Builder.CreateICmpNE(FloorTripRem, ConstantInt::get(IVType, 0));
 
     FloorTripOverflow = Builder.CreateZExt(FloorTripOverflow, IVType);
-    FloorTripCount =
-        Builder.CreateAdd(FloorTripCount, FloorTripOverflow,
+    Value *FloorTripCount =
+        Builder.CreateAdd(FloorCompleteTripCount, FloorTripOverflow,
                           "omp_floor" + Twine(i) + ".tripcount", true);
 
     // Remember some values for later use.
+    FloorCompleteCount.push_back(FloorCompleteTripCount);
     FloorCount.push_back(FloorTripCount);
     FloorRems.push_back(FloorTripRem);
   }
@@ -5660,7 +5661,7 @@ OpenMPIRBuilder::tileLoops(DebugLoc DL, ArrayRef<CanonicalLoopInfo *> Loops,
     Value *TileSize = TileSizes[i];
 
     Value *FloorIsEpilogue =
-        Builder.CreateICmpEQ(FloorLoop->getIndVar(), FloorCount[i]);
+        Builder.CreateICmpEQ(FloorLoop->getIndVar(), FloorCompleteCount[i]);
     Value *TileTripCount =
         Builder.CreateSelect(FloorIsEpilogue, FloorRems[i], TileSize);