[llvm-branch-commits] [llvm] [LoopInterchange] Add test for extra reduction use in inner loop (NFC) (PR #203240)
Ryotaro Kasuga via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Jun 11 03:56:46 PDT 2026
https://github.com/kasuga-fj updated https://github.com/llvm/llvm-project/pull/203240
>From 8ccd62c9b5997c8977eb0fdb0b43408b5c4b4669 Mon Sep 17 00:00:00 2001
From: Ryotaro Kasuga <kasuga.ryotaro at fujitsu.com>
Date: Thu, 11 Jun 2026 09:09:40 +0000
Subject: [PATCH] [LoopInterchange] Add test for extra reduction use in inner
loop (NFC)
---
.../reduction-extra-use-in-inner-loop.ll | 281 ++++++++++++++++++
1 file changed, 281 insertions(+)
create mode 100644 llvm/test/Transforms/LoopInterchange/reduction-extra-use-in-inner-loop.ll
diff --git a/llvm/test/Transforms/LoopInterchange/reduction-extra-use-in-inner-loop.ll b/llvm/test/Transforms/LoopInterchange/reduction-extra-use-in-inner-loop.ll
new file mode 100644
index 0000000000000..12493e954444f
--- /dev/null
+++ b/llvm/test/Transforms/LoopInterchange/reduction-extra-use-in-inner-loop.ll
@@ -0,0 +1,281 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt < %s -passes=loop-interchange -loop-interchange-profitabilities=ignore -S | FileCheck %s
+
+; sum = 0;
+; for (i = 0, sum_i = sum; i < 2; i++)
+; for (j = 0; j < 2; j++) {
+; sum += A[j][i];
+; B[j][i] = sum_i;
+; }
+;
+; Interchanging the loops will become as follows:
+;
+; sum = 0;
+; for (j = 0, sum_j = sum; j < 2; j++)
+; for (i = 0; i < 2; i++) {
+; sum += A[j][i];
+; B[j][i] = sum_j;
+; }
+;
+; This is invalid transformation. Consider the case when `A` is as follows:
+;
+; A = {{ 0, 0 }, { 1, 1 }}
+;
+; In this case, `sum_i` evolves 0 -> 1, while `sum_j` evolves 0 -> 0.
+;
+define i8 @extra_reduction_use_in_inner0(ptr noalias %A, ptr noalias %B) {
+; CHECK-LABEL: define i8 @extra_reduction_use_in_inner0(
+; CHECK-SAME: ptr noalias [[A:%.*]], ptr noalias [[B:%.*]]) {
+; CHECK-NEXT: [[INNER_PREHEADER:.*:]]
+; CHECK-NEXT: br label %[[INNER:.*]]
+; CHECK: [[OUTER_HEADER_PREHEADER1:.*]]:
+; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER:.*]]
+; CHECK: [[OUTER_HEADER_PREHEADER]]:
+; CHECK-NEXT: [[I:%.*]] = phi i64 [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ], [ 0, %[[OUTER_HEADER_PREHEADER1]] ]
+; CHECK-NEXT: [[SUM_INNER:%.*]] = phi i8 [ [[SUM_NEXT:%.*]], %[[OUTER_LATCH]] ], [ [[SUM:%.*]], %[[OUTER_HEADER_PREHEADER1]] ]
+; CHECK-NEXT: br label %[[INNER_SPLIT1:.*]]
+; CHECK: [[INNER]]:
+; CHECK-NEXT: br label %[[INNER1:.*]]
+; CHECK: [[INNER1]]:
+; CHECK-NEXT: [[J:%.*]] = phi i64 [ [[TMP2:%.*]], %[[INNER_SPLIT:.*]] ], [ 0, %[[INNER]] ]
+; CHECK-NEXT: [[SUM]] = phi i8 [ [[SUM_LCSSA:%.*]], %[[INNER_SPLIT]] ], [ 0, %[[INNER]] ]
+; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER1]]
+; CHECK: [[INNER_SPLIT1]]:
+; CHECK-NEXT: [[GEP_A:%.*]] = getelementptr [2 x i8], ptr [[A]], i64 [[J]], i64 [[I]]
+; CHECK-NEXT: [[A:%.*]] = load i8, ptr [[GEP_A]], align 1
+; CHECK-NEXT: [[SUM_NEXT]] = add i8 [[SUM_INNER]], [[A]]
+; CHECK-NEXT: [[GEP_B:%.*]] = getelementptr [2 x i8], ptr [[B]], i64 [[J]], i64 [[I]]
+; CHECK-NEXT: store i8 [[SUM]], ptr [[GEP_B]], align 1
+; CHECK-NEXT: [[TMP0:%.*]] = add i64 [[J]], 1
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[TMP0]], 2
+; CHECK-NEXT: br label %[[OUTER_LATCH]]
+; CHECK: [[INNER_SPLIT]]:
+; CHECK-NEXT: [[SUM_LCSSA]] = phi i8 [ [[SUM_NEXT]], %[[OUTER_LATCH]] ]
+; CHECK-NEXT: [[TMP2]] = add i64 [[J]], 1
+; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i64 [[TMP2]], 2
+; CHECK-NEXT: br i1 [[TMP3]], label %[[EXIT:.*]], label %[[INNER1]]
+; CHECK: [[OUTER_LATCH]]:
+; CHECK-NEXT: [[I_NEXT]] = add i64 [[I]], 1
+; CHECK-NEXT: [[EC_I:%.*]] = icmp eq i64 [[I_NEXT]], 2
+; CHECK-NEXT: br i1 [[EC_I]], label %[[INNER_SPLIT]], label %[[OUTER_HEADER_PREHEADER]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[RES:%.*]] = phi i8 [ [[SUM_LCSSA]], %[[INNER_SPLIT]] ]
+; CHECK-NEXT: ret i8 [[RES]]
+;
+entry:
+ br label %outer.header
+
+outer.header:
+ %i = phi i64 [ 0, %entry ], [ %i.next, %outer.latch ]
+ %sum.outer = phi i8 [ 0, %entry ], [ %sum.lcssa, %outer.latch ]
+ br label %inner
+
+inner:
+ %j = phi i64 [ 0, %outer.header ], [ %j.next, %inner ]
+ %sum.inner = phi i8 [ %sum.outer, %outer.header ], [ %sum.inner.next, %inner ]
+ %gep.A = getelementptr [2 x i8], ptr %A, i64 %j, i64 %i
+ %a = load i8, ptr %gep.A
+ %sum.inner.next = add i8 %sum.inner, %a
+ %gep.B = getelementptr [2 x i8], ptr %B, i64 %j, i64 %i
+ store i8 %sum.outer, ptr %gep.B
+ %j.next = add i64 %j, 1
+ %ec.j = icmp eq i64 %j.next, 2
+ br i1 %ec.j, label %outer.latch, label %inner
+
+outer.latch:
+ %sum.lcssa = phi i8 [ %sum.inner.next, %inner ]
+ %i.next = add i64 %i, 1
+ %ec.i = icmp eq i64 %i.next, 2
+ br i1 %ec.i, label %exit, label %outer.header
+
+exit:
+ %res = phi i8 [ %sum.lcssa, %outer.latch ]
+ ret i8 %res
+}
+
+; sum = 0;
+; for (i = 0; i < 2; i++)
+; for (j = 0; j < 2; j++) {
+; sum += A[j][i];
+; B[j][i] = sum;
+; }
+;
+; Interchanging the loops will become as follows:
+;
+; sum = 0;
+; for (j = 0; j < 2; j++)
+; for (i = 0; i < 2; i++) {
+; sum += A[j][i];
+; B[j][i] = sum;
+; }
+;
+; This is invalid transformation. Consider the case when `A` is as follows:
+;
+; A = {{ 0, 1 }, { 0, 0 }}
+;
+; In this case, in the original loops, `sum` evolves 0 -> 0 -> 1 -> 1, while in
+; the interchanged loops, `sum` evolves 0 -> 1 -> 1 -> 1
+;
+define i8 @extra_reduction_use_in_inner1(ptr noalias %A, ptr noalias %B) {
+; CHECK-LABEL: define i8 @extra_reduction_use_in_inner1(
+; CHECK-SAME: ptr noalias [[A:%.*]], ptr noalias [[B:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: br label %[[OUTER_HEADER:.*]]
+; CHECK: [[OUTER_HEADER]]:
+; CHECK-NEXT: [[I:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ]
+; CHECK-NEXT: [[SUM_OUTER:%.*]] = phi i8 [ 0, %[[ENTRY]] ], [ [[SUM_LCSSA:%.*]], %[[OUTER_LATCH]] ]
+; CHECK-NEXT: br label %[[INNER:.*]]
+; CHECK: [[INNER]]:
+; CHECK-NEXT: [[J:%.*]] = phi i64 [ 0, %[[OUTER_HEADER]] ], [ [[J_NEXT:%.*]], %[[INNER]] ]
+; CHECK-NEXT: [[SUM_INNER:%.*]] = phi i8 [ [[SUM_OUTER]], %[[OUTER_HEADER]] ], [ [[SUM_NEXT:%.*]], %[[INNER]] ]
+; CHECK-NEXT: [[GEP_A:%.*]] = getelementptr [2 x i8], ptr [[A]], i64 [[J]], i64 [[I]]
+; CHECK-NEXT: [[A:%.*]] = load i8, ptr [[GEP_A]], align 1
+; CHECK-NEXT: [[SUM_NEXT]] = add i8 [[SUM_INNER]], [[A]]
+; CHECK-NEXT: [[GEP_B:%.*]] = getelementptr [2 x i8], ptr [[B]], i64 [[J]], i64 [[I]]
+; CHECK-NEXT: store i8 [[SUM_NEXT]], ptr [[GEP_B]], align 1
+; CHECK-NEXT: [[J_NEXT]] = add i64 [[J]], 1
+; CHECK-NEXT: [[EC_J:%.*]] = icmp eq i64 [[J_NEXT]], 2
+; CHECK-NEXT: br i1 [[EC_J]], label %[[OUTER_LATCH]], label %[[INNER]]
+; CHECK: [[OUTER_LATCH]]:
+; CHECK-NEXT: [[SUM_LCSSA]] = phi i8 [ [[SUM_NEXT]], %[[INNER]] ]
+; CHECK-NEXT: [[I_NEXT]] = add i64 [[I]], 1
+; CHECK-NEXT: [[EC_I:%.*]] = icmp eq i64 [[I_NEXT]], 2
+; CHECK-NEXT: br i1 [[EC_I]], label %[[EXIT:.*]], label %[[OUTER_HEADER]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[RES:%.*]] = phi i8 [ [[SUM_LCSSA]], %[[OUTER_LATCH]] ]
+; CHECK-NEXT: ret i8 [[RES]]
+;
+entry:
+ br label %outer.header
+
+outer.header:
+ %i = phi i64 [ 0, %entry ], [ %i.next, %outer.latch ]
+ %sum.outer = phi i8 [ 0, %entry ], [ %sum.lcssa, %outer.latch ]
+ br label %inner
+
+inner:
+ %j = phi i64 [ 0, %outer.header ], [ %j.next, %inner ]
+ %sum.inner = phi i8 [ %sum.outer, %outer.header ], [ %sum.inner.next, %inner ]
+ %gep.A = getelementptr [2 x i8], ptr %A, i64 %j, i64 %i
+ %a = load i8, ptr %gep.A
+ %sum.inner.next = add i8 %sum.inner, %a
+ %gep.B = getelementptr [2 x i8], ptr %B, i64 %j, i64 %i
+ store i8 %sum.inner.next, ptr %gep.B
+ %j.next = add i64 %j, 1
+ %ec.j = icmp eq i64 %j.next, 2
+ br i1 %ec.j, label %outer.latch, label %inner
+
+outer.latch:
+ %sum.lcssa = phi i8 [ %sum.inner.next, %inner ]
+ %i.next = add i64 %i, 1
+ %ec.i = icmp eq i64 %i.next, 2
+ br i1 %ec.i, label %exit, label %outer.header
+
+exit:
+ %res = phi i8 [ %sum.lcssa, %outer.latch ]
+ ret i8 %res
+}
+
+; sum = 0;
+; for (i = 0, sum_i = sum; i < 2; i++)
+; for (j = 0; j < 2; j++)
+; for (k = 0; k < 2; k++) {
+; sum += A[j][i];
+; B[j][i] = sum_i;
+; }
+;
+; In this case, interchanging the j-loop and the k-loop is legal.
+;
+define i8 @extra_reduction_use_in_inner2(ptr noalias %A, ptr noalias %B) {
+; CHECK-LABEL: define i8 @extra_reduction_use_in_inner2(
+; CHECK-SAME: ptr noalias [[A:%.*]], ptr noalias [[B:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: br label %[[OUTER_HEADER:.*]]
+; CHECK: [[OUTER_HEADER]]:
+; CHECK-NEXT: [[I:%.*]] = phi i64 [ 0, %[[ENTRY]] ], [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ]
+; CHECK-NEXT: [[SUM_OUTER:%.*]] = phi i8 [ 0, %[[ENTRY]] ], [ [[SUM_OUTER_LCSSA:%.*]], %[[OUTER_LATCH]] ]
+; CHECK-NEXT: br label %[[MIDDLE_HEADER_PREHEADER:.*]]
+; CHECK: [[MIDDLE_HEADER_PREHEADER]]:
+; CHECK-NEXT: br label %[[MIDDLE_HEADER:.*]]
+; CHECK: [[MIDDLE_HEADER]]:
+; CHECK-NEXT: [[J:%.*]] = phi i64 [ [[TMP2:%.*]], %[[MIDDLE_LATCH_SPLIT:.*]] ], [ 0, %[[MIDDLE_HEADER_PREHEADER]] ]
+; CHECK-NEXT: [[SUM_MIDDLE:%.*]] = phi i8 [ [[SUM_MIDDLE_LCSSA:%.*]], %[[MIDDLE_LATCH_SPLIT]] ], [ [[SUM_OUTER]], %[[MIDDLE_HEADER_PREHEADER]] ]
+; CHECK-NEXT: br label %[[INNER_PREHEADER:.*]]
+; CHECK: [[INNER_PREHEADER]]:
+; CHECK-NEXT: br label %[[INNER:.*]]
+; CHECK: [[INNER]]:
+; CHECK-NEXT: [[K:%.*]] = phi i64 [ [[TMP0:%.*]], %[[INNER_SPLIT:.*]] ], [ 0, %[[INNER_PREHEADER]] ]
+; CHECK-NEXT: [[SUM_INNER:%.*]] = phi i8 [ [[SUM_INNER_NEXT:%.*]], %[[INNER_SPLIT]] ], [ [[SUM_MIDDLE]], %[[INNER_PREHEADER]] ]
+; CHECK-NEXT: br label %[[INNER_SPLIT1:.*]]
+; CHECK: [[INNER_SPLIT1]]:
+; CHECK-NEXT: [[GEP_A:%.*]] = getelementptr [2 x [2 x i8]], ptr [[A]], i64 [[K]], i64 [[J]], i64 [[I]]
+; CHECK-NEXT: [[A:%.*]] = load i8, ptr [[GEP_A]], align 1
+; CHECK-NEXT: [[SUM_INNER_NEXT]] = add i8 [[SUM_INNER]], [[A]]
+; CHECK-NEXT: [[GEP_B:%.*]] = getelementptr [2 x [2 x i8]], ptr [[B]], i64 [[K]], i64 [[J]], i64 [[I]]
+; CHECK-NEXT: store i8 [[SUM_OUTER]], ptr [[GEP_B]], align 1
+; CHECK-NEXT: [[K_NEXT:%.*]] = add i64 [[K]], 1
+; CHECK-NEXT: [[EC_K:%.*]] = icmp eq i64 [[K_NEXT]], 2
+; CHECK-NEXT: br label %[[MIDDLE_LATCH:.*]]
+; CHECK: [[INNER_SPLIT]]:
+; CHECK-NEXT: [[TMP0]] = add i64 [[K]], 1
+; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[TMP0]], 2
+; CHECK-NEXT: br i1 [[TMP1]], label %[[MIDDLE_LATCH_SPLIT]], label %[[INNER]]
+; CHECK: [[MIDDLE_LATCH]]:
+; CHECK-NEXT: [[J_NEXT:%.*]] = add i64 [[J]], 1
+; CHECK-NEXT: [[EC_J:%.*]] = icmp eq i64 [[J_NEXT]], 2
+; CHECK-NEXT: br label %[[INNER_SPLIT]]
+; CHECK: [[MIDDLE_LATCH_SPLIT]]:
+; CHECK-NEXT: [[SUM_MIDDLE_LCSSA]] = phi i8 [ [[SUM_INNER_NEXT]], %[[INNER_SPLIT]] ]
+; CHECK-NEXT: [[TMP2]] = add i64 [[J]], 1
+; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i64 [[TMP2]], 2
+; CHECK-NEXT: br i1 [[TMP3]], label %[[OUTER_LATCH]], label %[[MIDDLE_HEADER]]
+; CHECK: [[OUTER_LATCH]]:
+; CHECK-NEXT: [[SUM_OUTER_LCSSA]] = phi i8 [ [[SUM_MIDDLE_LCSSA]], %[[MIDDLE_LATCH_SPLIT]] ]
+; CHECK-NEXT: [[I_NEXT]] = add i64 [[I]], 1
+; CHECK-NEXT: [[EC_I:%.*]] = icmp eq i64 [[I_NEXT]], 2
+; CHECK-NEXT: br i1 [[EC_I]], label %[[EXIT:.*]], label %[[OUTER_HEADER]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[RES:%.*]] = phi i8 [ [[SUM_OUTER_LCSSA]], %[[OUTER_LATCH]] ]
+; CHECK-NEXT: ret i8 [[RES]]
+;
+entry:
+ br label %outer.header
+
+outer.header:
+ %i = phi i64 [ 0, %entry ], [ %i.next, %outer.latch ]
+ %sum.outer = phi i8 [ 0, %entry ], [ %sum.outer.lcssa, %outer.latch ]
+ br label %middle.header
+
+middle.header:
+ %j = phi i64 [ 0, %outer.header ], [ %j.next, %middle.latch ]
+ %sum.middle = phi i8 [ %sum.outer, %outer.header ], [ %sum.middle.lcssa, %middle.latch ]
+ br label %inner
+
+inner:
+ %k = phi i64 [ 0, %middle.header ], [ %k.next, %inner ]
+ %sum.inner = phi i8 [ %sum.middle, %middle.header ], [ %sum.inner.next, %inner ]
+ %gep.A = getelementptr [2 x [2 x i8]], ptr %A, i64 %k, i64 %j, i64 %i
+ %a = load i8, ptr %gep.A
+ %sum.inner.next = add i8 %sum.inner, %a
+ %gep.B = getelementptr [2 x [2 x i8]], ptr %B, i64 %k, i64 %j, i64 %i
+ store i8 %sum.outer, ptr %gep.B
+ %k.next = add i64 %k, 1
+ %ec.k = icmp eq i64 %k.next, 2
+ br i1 %ec.k, label %middle.latch, label %inner
+
+middle.latch:
+ %sum.middle.lcssa = phi i8 [ %sum.inner.next, %inner ]
+ %j.next = add i64 %j, 1
+ %ec.j = icmp eq i64 %j.next, 2
+ br i1 %ec.j, label %outer.latch, label %middle.header
+
+outer.latch:
+ %sum.outer.lcssa = phi i8 [ %sum.middle.lcssa, %middle.latch ]
+ %i.next = add i64 %i, 1
+ %ec.i = icmp eq i64 %i.next, 2
+ br i1 %ec.i, label %exit, label %outer.header
+
+exit:
+ %res = phi i8 [ %sum.outer.lcssa, %outer.latch ]
+ ret i8 %res
+}
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