[llvm] eee9755 - [LV] Refine check to find epilogue IV resume value.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 1 12:55:05 PDT 2025
Author: Florian Hahn
Date: 2025-08-01T20:54:39+01:00
New Revision: eee9755881bf39bc15e6e05697abbbfabb51cb78
URL: https://github.com/llvm/llvm-project/commit/eee9755881bf39bc15e6e05697abbbfabb51cb78
DIFF: https://github.com/llvm/llvm-project/commit/eee9755881bf39bc15e6e05697abbbfabb51cb78.diff
LOG: [LV] Refine check to find epilogue IV resume value.
Make sure to check that the vector trip count is containedin the list of
incoming values to serve as tie-breaker with phis with all-zero incoming
values.
Fixes https://github.com/llvm/llvm-project/issues/151686.
Added:
Modified:
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-inductions.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 20528089c0008..b4ea70e0e5cc2 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -9788,6 +9788,10 @@ preparePlanForEpilogueVectorLoop(VPlan &Plan, Loop *L,
match(
P.getIncomingValueForBlock(EPI.MainLoopIterationCountCheck),
m_SpecificInt(0)) &&
+ any_of(P.incoming_values(),
+ [&EPI](Value *Inc) {
+ return Inc == EPI.VectorTripCount;
+ }) &&
all_of(P.incoming_values(), [&EPI](Value *Inc) {
return Inc == EPI.VectorTripCount ||
match(Inc, m_SpecificInt(0));
diff --git a/llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-inductions.ll b/llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-inductions.ll
index 7c749810caf23..90d261b78c27c 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-inductions.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-inductions.ll
@@ -250,3 +250,78 @@ loop:
exit:
ret void
}
+
+; Test case for https://github.com/llvm/llvm-project/issues/151686.
+define i8 @multiple_inductions_start_at_0() {
+; CHECK-LABEL: @multiple_inductions_start_at_0(
+; CHECK-NEXT: iter.check:
+; CHECK-NEXT: br i1 false, label [[VEC_EPILOG_SCALAR_PH:%.*]], label [[VECTOR_MAIN_LOOP_ITER_CHECK:%.*]]
+; CHECK: vector.main.loop.iter.check:
+; CHECK-NEXT: br i1 false, label [[VEC_EPILOG_PH:%.*]], label [[VECTOR_PH:%.*]]
+; CHECK: vector.ph:
+; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
+; CHECK: vector.body:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i32 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT: [[VEC_IND:%.*]] = phi <32 x i8> [ zeroinitializer, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT: [[STEP_ADD:%.*]] = add <32 x i8> [[VEC_IND]], zeroinitializer
+; CHECK-NEXT: [[STEP_ADD_2:%.*]] = add <32 x i8> [[STEP_ADD]], zeroinitializer
+; CHECK-NEXT: [[STEP_ADD_3:%.*]] = add <32 x i8> [[STEP_ADD_2]], zeroinitializer
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 128
+; CHECK-NEXT: [[VEC_IND_NEXT]] = add <32 x i8> [[STEP_ADD_3]], zeroinitializer
+; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i32 [[INDEX_NEXT]], 1024
+; CHECK-NEXT: br i1 [[TMP0]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP8:![0-9]+]]
+; CHECK: middle.block:
+; CHECK-NEXT: [[TMP1:%.*]] = extractelement <32 x i8> [[STEP_ADD_3]], i32 31
+; CHECK-NEXT: br i1 false, label [[EXIT:%.*]], label [[VEC_EPILOG_ITER_CHECK:%.*]]
+; CHECK: vec.epilog.iter.check:
+; CHECK-NEXT: br i1 false, label [[VEC_EPILOG_SCALAR_PH]], label [[VEC_EPILOG_PH]]
+; CHECK: vec.epilog.ph:
+; CHECK-NEXT: [[VEC_EPILOG_RESUME_VAL:%.*]] = phi i32 [ 1024, [[VEC_EPILOG_ITER_CHECK]] ], [ 0, [[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i32 [ 0, [[VEC_EPILOG_ITER_CHECK]] ], [ 0, [[VECTOR_MAIN_LOOP_ITER_CHECK]] ]
+; CHECK-NEXT: [[TMP2:%.*]] = trunc i32 [[BC_RESUME_VAL]] to i8
+; CHECK-NEXT: [[BROADCAST_SPLATINSERT:%.*]] = insertelement <4 x i8> poison, i8 [[TMP2]], i64 0
+; CHECK-NEXT: [[BROADCAST_SPLAT:%.*]] = shufflevector <4 x i8> [[BROADCAST_SPLATINSERT]], <4 x i8> poison, <4 x i32> zeroinitializer
+; CHECK-NEXT: [[INDUCTION:%.*]] = add <4 x i8> [[BROADCAST_SPLAT]], zeroinitializer
+; CHECK-NEXT: br label [[VEC_EPILOG_VECTOR_BODY:%.*]]
+; CHECK: vec.epilog.vector.body:
+; CHECK-NEXT: [[INDEX1:%.*]] = phi i32 [ [[VEC_EPILOG_RESUME_VAL]], [[VEC_EPILOG_PH]] ], [ [[INDEX_NEXT3:%.*]], [[VEC_EPILOG_VECTOR_BODY]] ]
+; CHECK-NEXT: [[VEC_IND2:%.*]] = phi <4 x i8> [ [[INDUCTION]], [[VEC_EPILOG_PH]] ], [ [[VEC_IND_NEXT4:%.*]], [[VEC_EPILOG_VECTOR_BODY]] ]
+; CHECK-NEXT: [[INDEX_NEXT3]] = add nuw i32 [[INDEX1]], 4
+; CHECK-NEXT: [[VEC_IND_NEXT4]] = add <4 x i8> [[VEC_IND2]], zeroinitializer
+; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i32 [[INDEX_NEXT3]], 1052
+; CHECK-NEXT: br i1 [[TMP3]], label [[VEC_EPILOG_MIDDLE_BLOCK:%.*]], label [[VEC_EPILOG_VECTOR_BODY]], !llvm.loop [[LOOP9:![0-9]+]]
+; CHECK: vec.epilog.middle.block:
+; CHECK-NEXT: [[TMP4:%.*]] = extractelement <4 x i8> [[VEC_IND2]], i32 3
+; CHECK-NEXT: br i1 true, label [[EXIT]], label [[VEC_EPILOG_SCALAR_PH]]
+; CHECK: vec.epilog.scalar.ph:
+; CHECK-NEXT: [[BC_RESUME_VAL5:%.*]] = phi i32 [ 1052, [[VEC_EPILOG_MIDDLE_BLOCK]] ], [ 1024, [[VEC_EPILOG_ITER_CHECK]] ], [ 0, [[ITER_CHECK:%.*]] ]
+; CHECK-NEXT: [[BC_RESUME_VAL6:%.*]] = phi i32 [ -469762048, [[VEC_EPILOG_MIDDLE_BLOCK]] ], [ 0, [[VEC_EPILOG_ITER_CHECK]] ], [ 0, [[ITER_CHECK]] ]
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: [[IV:%.*]] = phi i32 [ [[BC_RESUME_VAL5]], [[VEC_EPILOG_SCALAR_PH]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT: [[IV_2:%.*]] = phi i32 [ [[BC_RESUME_VAL6]], [[VEC_EPILOG_SCALAR_PH]] ], [ [[ADD:%.*]], [[LOOP]] ]
+; CHECK-NEXT: [[ADD]] = add i32 [[IV_2]], -16777216
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc i32 [[IV_2]] to i8
+; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
+; CHECK-NEXT: [[EC:%.*]] = icmp ugt i32 [[IV]], 1050
+; CHECK-NEXT: br i1 [[EC]], label [[EXIT]], label [[LOOP]], !llvm.loop [[LOOP10:![0-9]+]]
+; CHECK: exit:
+; CHECK-NEXT: [[RES:%.*]] = phi i8 [ [[TRUNC]], [[LOOP]] ], [ [[TMP1]], [[MIDDLE_BLOCK]] ], [ [[TMP4]], [[VEC_EPILOG_MIDDLE_BLOCK]] ]
+; CHECK-NEXT: ret i8 [[RES]]
+;
+entry:
+ br label %loop
+
+loop:
+ %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
+ %iv.2 = phi i32 [ 0, %entry ], [ %add, %loop ]
+ %add = add i32 %iv.2, -16777216
+ %trunc = trunc i32 %iv.2 to i8
+ %iv.next = add i32 %iv, 1
+ %ec = icmp ugt i32 %iv, 1050
+ br i1 %ec, label %exit, label %loop
+
+exit:
+ %res = phi i8 [ %trunc, %loop ]
+ ret i8 %res
+}
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