[llvm] [LV] Disable fold tail by masking - when induction vars used outside (PR #81609)
Niwin Anto via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 29 04:46:51 PST 2024
https://github.com/niwinanto updated https://github.com/llvm/llvm-project/pull/81609
>From 5d2f84b4c18b1d03ce6fa52ce1460ae46ec2cb04 Mon Sep 17 00:00:00 2001
From: Niwin Anto <niwin.anto at hightec-rt.com>
Date: Tue, 13 Feb 2024 15:33:07 +0100
Subject: [PATCH 1/2] [LV] Disable fold tail by masking - when induction vars
used outside
---
.../Vectorize/LoopVectorizationLegality.cpp | 13 +++
...o-fold-tail-by-masking-iv-external-uses.ll | 85 +++++++++++++++++++
2 files changed, 98 insertions(+)
create mode 100644 llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 37a356c43e29a4..d33743e74cbe31 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -1552,6 +1552,19 @@ bool LoopVectorizationLegality::prepareToFoldTailByMasking() {
}
}
+ for (const auto &Entry : getInductionVars()) {
+ PHINode *OrigPhi = Entry.first;
+ for (User *U : OrigPhi->users()) {
+ auto *UI = cast<Instruction>(U);
+ if (!TheLoop->contains(UI)) {
+ LLVM_DEBUG(dbgs() << "LV: Cannot fold tail by masking, loop IV has an "
+ "outside user for "
+ << *UI << "\n");
+ return false;
+ }
+ }
+ }
+
// The list of pointers that we can safely read and write to remains empty.
SmallPtrSet<Value *, 8> SafePointers;
diff --git a/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll b/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll
new file mode 100644
index 00000000000000..f7379df934bd77
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll
@@ -0,0 +1,85 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=loop-vectorize -S | FileCheck %s
+
+
+; #include <stdio.h>
+; #define SIZE 17
+;
+; unsigned char result;
+; unsigned char arr_1[SIZE];
+;
+; __attribute__((__noinline__))
+; void test(int limit, unsigned char val, int arr_2[SIZE][SIZE][SIZE]) {
+; #pragma clang loop vectorize_predicate(enable)
+; for (short i_5 = 0; i_5 < limit; i_5++) {
+; arr_1 [i_5] = val;
+; result = arr_2[0][0][i_5] != arr_2[i_5][i_5][0];
+; }
+; }
+;
+;int main(void) {
+; int arr_2[SIZE][SIZE][SIZE];
+;
+; __builtin_memset(arr_2, 1, sizeof(arr_2));
+;
+; test(SIZE, 0, arr_2);
+; printf("%hu \n", result);
+;}
+; clang miss-compiles the above code
+; with vectorize_predicate(enable), result is 0 and 1 without.
+
+
+ at result = global i8 0, align 1
+ at arr_17 = global [17 x i8] zeroinitializer, align 1
+ at a = external global i8, align 1
+
+define void @test(i32 %limit, i8 zeroext %val, ptr readonly %arr_14) {
+; CHECK-LABEL: @test(
+; CHECK-NOT: pred.store.if:
+; CHECK-NOT: pred.store.continue:
+;
+entry:
+ %cmp18 = icmp sgt i32 %limit, 0
+ br i1 %cmp18, label %for.body.preheader, label %for.cond.cleanup
+
+for.body.preheader: ; preds = %entry
+ br label %for.body
+
+for.cond.for.cond.cleanup_crit_edge: ; preds = %for.body
+ %conv20.lcssa = phi i32 [ %conv20, %for.body ]
+ %arrayidx4 = getelementptr inbounds [17 x i32], ptr %arr_14, i32 0, i32 %conv20.lcssa
+ %0 = load i32, ptr %arrayidx4, align 4, !tbaa !4
+ %arrayidx8 = getelementptr inbounds [17 x [17 x i32]], ptr %arr_14, i32 %conv20.lcssa, i32 %conv20.lcssa
+ %1 = load i32, ptr %arrayidx8, align 4, !tbaa !4
+ %cmp10 = icmp ne i32 %0, %1
+ %conv11 = zext i1 %cmp10 to i8
+ store i8 %conv11, ptr @result, align 1, !tbaa !8
+ br label %for.cond.cleanup
+
+for.cond.cleanup: ; preds = %for.cond.for.cond.cleanup_crit_edge, %entry
+ ret void
+
+for.body: ; preds = %for.body.preheader, %for.body
+ %conv20 = phi i32 [ %conv, %for.body ], [ 0, %for.body.preheader ]
+ %i_5.019 = phi i16 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+ %arrayidx = getelementptr inbounds [17 x i8], ptr @arr_17, i32 0, i32 %conv20
+ store i8 %val, ptr %arrayidx, align 1, !tbaa !8
+ %inc = add i16 %i_5.019, 1
+ %conv = sext i16 %inc to i32
+ %cmp = icmp slt i32 %conv, %limit
+ br i1 %cmp, label %for.body, label %for.cond.for.cond.cleanup_crit_edge, !llvm.loop !9
+}
+
+
+
+!4 = !{!5, !5, i64 0}
+!5 = !{!"int", !6, i64 0}
+!6 = !{!"omnipotent char", !7, i64 0}
+!7 = !{!"Simple C++ TBAA"}
+!8 = !{!6, !6, i64 0}
+!9 = distinct !{!9, !10, !11, !12, !13, !14}
+!10 = !{!"llvm.loop.mustprogress"}
+!11 = !{!"llvm.loop.vectorize.predicate.enable", i1 true}
+!12 = !{!"llvm.loop.vectorize.width", i32 2}
+!13 = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
+!14 = !{!"llvm.loop.vectorize.enable", i1 true}
>From 5b6abb1989df145d06c48862c3b12508446dd948 Mon Sep 17 00:00:00 2001
From: Niwin Anto <niwin.anto at hightec-rt.com>
Date: Tue, 13 Feb 2024 20:41:07 +0100
Subject: [PATCH 2/2] Code Review adjustments
---
...o-fold-tail-by-masking-iv-external-uses.ll | 187 +++++++++++-------
1 file changed, 112 insertions(+), 75 deletions(-)
diff --git a/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll b/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll
index f7379df934bd77..b26006d032816d 100644
--- a/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll
+++ b/llvm/test/Transforms/LoopVectorize/no-fold-tail-by-masking-iv-external-uses.ll
@@ -1,85 +1,122 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=loop-vectorize -S | FileCheck %s
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -passes=loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -S | FileCheck %s
-
-; #include <stdio.h>
-; #define SIZE 17
-;
-; unsigned char result;
-; unsigned char arr_1[SIZE];
-;
-; __attribute__((__noinline__))
-; void test(int limit, unsigned char val, int arr_2[SIZE][SIZE][SIZE]) {
-; #pragma clang loop vectorize_predicate(enable)
-; for (short i_5 = 0; i_5 < limit; i_5++) {
-; arr_1 [i_5] = val;
-; result = arr_2[0][0][i_5] != arr_2[i_5][i_5][0];
-; }
-; }
+define dso_local i32 @test(i32* nocapture %arr, i64 %n) {
+; The vectorizer should refuse to fold the tail by masking because
+; %conv is used outside of the loop. Test for this by checking that
+; %n.vec, the vector trip count, is rounded down to the next multiple of
+; 4. If folding the tail, it would have been rounded up instead.
;
-;int main(void) {
-; int arr_2[SIZE][SIZE][SIZE];
-;
-; __builtin_memset(arr_2, 1, sizeof(arr_2));
-;
-; test(SIZE, 0, arr_2);
-; printf("%hu \n", result);
-;}
-; clang miss-compiles the above code
-; with vectorize_predicate(enable), result is 0 and 1 without.
-
-
- at result = global i8 0, align 1
- at arr_17 = global [17 x i8] zeroinitializer, align 1
- at a = external global i8, align 1
-
-define void @test(i32 %limit, i8 zeroext %val, ptr readonly %arr_14) {
-; CHECK-LABEL: @test(
-; CHECK-NOT: pred.store.if:
-; CHECK-NOT: pred.store.continue:
+; CHECK-LABEL: define dso_local i32 @test(
+; CHECK-SAME: ptr nocapture [[ARR:%.*]], i64 [[N:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP1:%.*]] = icmp ugt i64 [[N]], 1
+; CHECK-NEXT: br i1 [[CMP1]], label [[PREHEADER:%.*]], label [[DONE:%.*]]
+; CHECK: preheader:
+; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[N]], -1
+; CHECK-NEXT: [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[TMP0]], 4
+; CHECK-NEXT: br i1 [[MIN_ITERS_CHECK]], label [[SCALAR_PH:%.*]], label [[VECTOR_SCEVCHECK:%.*]]
+; CHECK: vector.scevcheck:
+; CHECK-NEXT: [[TMP1:%.*]] = add i64 [[N]], -2
+; CHECK-NEXT: [[TMP2:%.*]] = trunc i64 [[TMP1]] to i8
+; CHECK-NEXT: [[TMP3:%.*]] = add i8 1, [[TMP2]]
+; CHECK-NEXT: [[TMP4:%.*]] = icmp ult i8 [[TMP3]], 1
+; CHECK-NEXT: [[TMP5:%.*]] = icmp ugt i64 [[TMP1]], 255
+; CHECK-NEXT: [[TMP6:%.*]] = or i1 [[TMP4]], [[TMP5]]
+; CHECK-NEXT: [[TMP7:%.*]] = trunc i64 [[TMP1]] to i8
+; CHECK-NEXT: [[TMP8:%.*]] = add i8 2, [[TMP7]]
+; CHECK-NEXT: [[TMP9:%.*]] = icmp ult i8 [[TMP8]], 2
+; CHECK-NEXT: [[TMP10:%.*]] = icmp ugt i64 [[TMP1]], 255
+; CHECK-NEXT: [[TMP11:%.*]] = or i1 [[TMP9]], [[TMP10]]
+; CHECK-NEXT: [[TMP12:%.*]] = or i1 [[TMP6]], [[TMP11]]
+; CHECK-NEXT: br i1 [[TMP12]], label [[SCALAR_PH]], label [[VECTOR_PH:%.*]]
+; CHECK: vector.ph:
+; CHECK-NEXT: [[N_MOD_VF:%.*]] = urem i64 [[TMP0]], 4
+; CHECK-NEXT: [[N_VEC:%.*]] = sub i64 [[TMP0]], [[N_MOD_VF]]
+; CHECK-NEXT: [[IND_END:%.*]] = add i64 1, [[N_VEC]]
+; CHECK-NEXT: [[DOTCAST:%.*]] = trunc i64 [[N_VEC]] to i8
+; CHECK-NEXT: [[IND_END1:%.*]] = add i8 1, [[DOTCAST]]
+; CHECK-NEXT: br label [[VECTOR_BODY:%.*]]
+; CHECK: vector.body:
+; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT: [[OFFSET_IDX:%.*]] = add i64 1, [[INDEX]]
+; CHECK-NEXT: [[TMP13:%.*]] = add i64 [[OFFSET_IDX]], 0
+; CHECK-NEXT: [[TMP14:%.*]] = add i64 [[OFFSET_IDX]], 1
+; CHECK-NEXT: [[TMP15:%.*]] = add i64 [[OFFSET_IDX]], 2
+; CHECK-NEXT: [[TMP16:%.*]] = add i64 [[OFFSET_IDX]], 3
+; CHECK-NEXT: [[TMP17:%.*]] = add nsw i64 [[TMP13]], -1
+; CHECK-NEXT: [[TMP18:%.*]] = getelementptr inbounds i32, ptr [[ARR]], i64 [[TMP17]]
+; CHECK-NEXT: [[TMP19:%.*]] = getelementptr inbounds i32, ptr [[TMP18]], i32 0
+; CHECK-NEXT: store <4 x i32> <i32 65, i32 65, i32 65, i32 65>, ptr [[TMP19]], align 4
+; CHECK-NEXT: [[INDEX_NEXT]] = add nuw i64 [[INDEX]], 4
+; CHECK-NEXT: [[TMP20:%.*]] = icmp eq i64 [[INDEX_NEXT]], [[N_VEC]]
+; CHECK-NEXT: br i1 [[TMP20]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
+; CHECK: middle.block:
+; CHECK-NEXT: [[CMP_N:%.*]] = icmp eq i64 [[TMP0]], [[N_VEC]]
+; CHECK-NEXT: [[CMO:%.*]] = sub i64 [[N_VEC]], 1
+; CHECK-NEXT: [[IND_ESCAPE:%.*]] = add i64 1, [[CMO]]
+; CHECK-NEXT: br i1 [[CMP_N]], label [[LOAD_VAL:%.*]], label [[SCALAR_PH]]
+; CHECK: scalar.ph:
+; CHECK-NEXT: [[BC_RESUME_VAL:%.*]] = phi i64 [ [[IND_END]], [[MIDDLE_BLOCK]] ], [ 1, [[PREHEADER]] ], [ 1, [[VECTOR_SCEVCHECK]] ]
+; CHECK-NEXT: [[BC_RESUME_VAL2:%.*]] = phi i8 [ [[IND_END1]], [[MIDDLE_BLOCK]] ], [ 1, [[PREHEADER]] ], [ 1, [[VECTOR_SCEVCHECK]] ]
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: [[CONV:%.*]] = phi i64 [ [[CONV2:%.*]], [[LOOP]] ], [ [[BC_RESUME_VAL]], [[SCALAR_PH]] ]
+; CHECK-NEXT: [[I:%.*]] = phi i8 [ [[INC:%.*]], [[LOOP]] ], [ [[BC_RESUME_VAL2]], [[SCALAR_PH]] ]
+; CHECK-NEXT: [[SUB:%.*]] = add nsw i64 [[CONV]], -1
+; CHECK-NEXT: [[PTR:%.*]] = getelementptr inbounds i32, ptr [[ARR]], i64 [[SUB]]
+; CHECK-NEXT: store i32 65, ptr [[PTR]], align 4
+; CHECK-NEXT: [[INC]] = add i8 [[I]], 1
+; CHECK-NEXT: [[CONV2]] = zext i8 [[INC]] to i64
+; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i64 [[CONV2]], [[N]]
+; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP]], label [[LOAD_VAL]], !llvm.loop [[LOOP4:![0-9]+]]
+; CHECK: load_val:
+; CHECK-NEXT: [[FINAL:%.*]] = phi i64 [ [[CONV]], [[LOOP]] ], [ [[IND_ESCAPE]], [[MIDDLE_BLOCK]] ]
+; CHECK-NEXT: [[PTR2:%.*]] = getelementptr inbounds i32, ptr [[ARR]], i64 [[FINAL]]
+; CHECK-NEXT: [[VAL:%.*]] = load i32, ptr [[PTR2]], align 4
+; CHECK-NEXT: br label [[DONE]]
+; CHECK: done:
+; CHECK-NEXT: [[VALUE:%.*]] = phi i32 [ [[VAL]], [[LOAD_VAL]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT: ret i32 [[VALUE]]
;
entry:
- %cmp18 = icmp sgt i32 %limit, 0
- br i1 %cmp18, label %for.body.preheader, label %for.cond.cleanup
+ %cmp1 = icmp ugt i64 %n, 1
+ br i1 %cmp1, label %preheader, label %done
-for.body.preheader: ; preds = %entry
- br label %for.body
+preheader:
+ br label %loop
-for.cond.for.cond.cleanup_crit_edge: ; preds = %for.body
- %conv20.lcssa = phi i32 [ %conv20, %for.body ]
- %arrayidx4 = getelementptr inbounds [17 x i32], ptr %arr_14, i32 0, i32 %conv20.lcssa
- %0 = load i32, ptr %arrayidx4, align 4, !tbaa !4
- %arrayidx8 = getelementptr inbounds [17 x [17 x i32]], ptr %arr_14, i32 %conv20.lcssa, i32 %conv20.lcssa
- %1 = load i32, ptr %arrayidx8, align 4, !tbaa !4
- %cmp10 = icmp ne i32 %0, %1
- %conv11 = zext i1 %cmp10 to i8
- store i8 %conv11, ptr @result, align 1, !tbaa !8
- br label %for.cond.cleanup
+loop:
+ %conv = phi i64 [ %conv2, %loop ], [ 1, %preheader ]
+ %i = phi i8 [ %inc, %loop ], [ 1, %preheader ]
+ %sub = add nsw i64 %conv, -1
+ %ptr = getelementptr inbounds i32, i32* %arr, i64 %sub
+ store i32 65, i32* %ptr, align 4
+ %inc = add i8 %i, 1
+ %conv2 = zext i8 %inc to i64
+ %cmp2 = icmp ult i64 %conv2, %n
+ br i1 %cmp2, label %loop, label %load_val, !llvm.loop !0
-for.cond.cleanup: ; preds = %for.cond.for.cond.cleanup_crit_edge, %entry
- ret void
-
-for.body: ; preds = %for.body.preheader, %for.body
- %conv20 = phi i32 [ %conv, %for.body ], [ 0, %for.body.preheader ]
- %i_5.019 = phi i16 [ %inc, %for.body ], [ 0, %for.body.preheader ]
- %arrayidx = getelementptr inbounds [17 x i8], ptr @arr_17, i32 0, i32 %conv20
- store i8 %val, ptr %arrayidx, align 1, !tbaa !8
- %inc = add i16 %i_5.019, 1
- %conv = sext i16 %inc to i32
- %cmp = icmp slt i32 %conv, %limit
- br i1 %cmp, label %for.body, label %for.cond.for.cond.cleanup_crit_edge, !llvm.loop !9
-}
+load_val:
+ %final = phi i64 [ %conv, %loop ]
+ %ptr2 = getelementptr inbounds i32, i32* %arr, i64 %final
+ %val = load i32, i32* %ptr2, align 4
+ br label %done
+done:
+ %value = phi i32 [ %val, %load_val ], [ 0, %entry ]
+ ret i32 %value
+}
-!4 = !{!5, !5, i64 0}
-!5 = !{!"int", !6, i64 0}
-!6 = !{!"omnipotent char", !7, i64 0}
-!7 = !{!"Simple C++ TBAA"}
-!8 = !{!6, !6, i64 0}
-!9 = distinct !{!9, !10, !11, !12, !13, !14}
-!10 = !{!"llvm.loop.mustprogress"}
-!11 = !{!"llvm.loop.vectorize.predicate.enable", i1 true}
-!12 = !{!"llvm.loop.vectorize.width", i32 2}
-!13 = !{!"llvm.loop.vectorize.scalable.enable", i1 false}
-!14 = !{!"llvm.loop.vectorize.enable", i1 true}
+!0 = distinct !{!0, !1, !2, !3}
+!1 = !{!"llvm.loop.unroll.disable"}
+!2 = !{!"llvm.loop.vectorize.predicate.enable", i1 true}
+!3 = !{!"llvm.loop.vectorize.enable", i1 true}
+;.
+; CHECK: [[LOOP0]] = distinct !{[[LOOP0]], [[META1:![0-9]+]], [[META2:![0-9]+]], [[META3:![0-9]+]]}
+; CHECK: [[META1]] = !{!"llvm.loop.unroll.disable"}
+; CHECK: [[META2]] = !{!"llvm.loop.isvectorized", i32 1}
+; CHECK: [[META3]] = !{!"llvm.loop.unroll.runtime.disable"}
+; CHECK: [[LOOP4]] = distinct !{[[LOOP4]], [[META1]], [[META2]]}
+;.
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