https://github.com/kasuga-fj updated https://github.com/llvm/llvm-project/pull/203241
>From cd2c82f05105af825ed5d99e8ab9f14ecc08900c Mon Sep 17 00:00:00 2001 From: Ryotaro Kasuga <[email protected]> Date: Thu, 11 Jun 2026 10:51:12 +0000 Subject: [PATCH] [LoopInterchange] Reject if outer reduction value has extra user --- .../lib/Transforms/Scalar/LoopInterchange.cpp | 20 +++++++++ .../reduction-extra-use-in-inner-loop.ll | 42 +++++++++---------- 2 files changed, 41 insertions(+), 21 deletions(-) diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp index 543f527941b29..c96dfc1025784 100644 --- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp +++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp @@ -1280,6 +1280,26 @@ bool LoopInterchangeLegality::checkInductionsAndReductions(Loop *OuterLoop) { }); return false; } + + // Reject if PHI has users other than InnerRedPhi. The typical case is + // as follows: + // + // o.header: + // %red.o = phi [ 0, ... ], [ %red.next, %o.latch ] + // br label %i.header + // + // i.header: + // %red.i = phi [ %red.o, %o.header ], [ %red.next, %i.latch ] + // br label %i.body + // + // i.body: + // store %red.o to %mem + // ... + // + if (!all_of(PHI.users(), + [InnerRedPhi](User *U) { return U == InnerRedPhi; })) + return false; + OuterInnerReductions.insert(&PHI); OuterInnerReductions.insert(InnerRedPhi); } else { 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 index 12493e954444f..a3626ebcf5046 100644 --- a/llvm/test/Transforms/LoopInterchange/reduction-extra-use-in-inner-loop.ll +++ b/llvm/test/Transforms/LoopInterchange/reduction-extra-use-in-inner-loop.ll @@ -26,38 +26,38 @@ 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: [[ENTRY:.*:]] +; CHECK-NEXT: br label %[[INNER_PREHEADER:.*]] +; CHECK: [[OUTER_HEADER_PREHEADER:.*]]: +; CHECK-NEXT: br label %[[OUTER_HEADER:.*]] +; CHECK: [[OUTER_HEADER]]: +; CHECK-NEXT: [[I:%.*]] = phi i64 [ [[I_NEXT:%.*]], %[[OUTER_LATCH:.*]] ], [ 0, %[[OUTER_HEADER_PREHEADER]] ] +; CHECK-NEXT: [[SUM_INNER:%.*]] = phi i8 [ [[SUM_INNER_NEXT:%.*]], %[[OUTER_LATCH]] ], [ [[SUM_OUTER:%.*]], %[[OUTER_HEADER_PREHEADER]] ] ; CHECK-NEXT: br label %[[INNER_SPLIT1:.*]] +; CHECK: [[INNER_PREHEADER]]: +; CHECK-NEXT: br label %[[INNER:.*]] ; 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-NEXT: [[J:%.*]] = phi i64 [ [[TMP0:%.*]], %[[INNER_SPLIT:.*]] ], [ 0, %[[INNER_PREHEADER]] ] +; CHECK-NEXT: [[SUM_OUTER]] = phi i8 [ [[SUM_LCSSA:%.*]], %[[INNER_SPLIT]] ], [ 0, %[[INNER_PREHEADER]] ] +; CHECK-NEXT: br label %[[OUTER_HEADER_PREHEADER]] ; 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: [[SUM_INNER_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: store i8 [[SUM_OUTER]], 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 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-NEXT: [[SUM_LCSSA]] = phi i8 [ [[SUM_INNER_NEXT]], %[[OUTER_LATCH]] ] +; CHECK-NEXT: [[TMP0]] = add i64 [[J]], 1 +; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i64 [[TMP0]], 2 +; CHECK-NEXT: br i1 [[TMP1]], label %[[EXIT:.*]], label %[[INNER]] ; 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-NEXT: br i1 [[EC_I]], label %[[INNER_SPLIT]], label %[[OUTER_HEADER]] ; CHECK: [[EXIT]]: ; CHECK-NEXT: [[RES:%.*]] = phi i8 [ [[SUM_LCSSA]], %[[INNER_SPLIT]] ] ; CHECK-NEXT: ret i8 [[RES]] _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
