[llvm] [LoopInterchange] Don't consider loops with BTC=0 (PR #167113)
Sjoerd Meijer via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 17 09:41:50 PST 2025
https://github.com/sjoerdmeijer updated https://github.com/llvm/llvm-project/pull/167113
>From e72522a79fde564ed7badd7b833281c7f4f38197 Mon Sep 17 00:00:00 2001
From: Sjoerd Meijer <smeijer at nvidia.com>
Date: Fri, 7 Nov 2025 06:23:51 -0800
Subject: [PATCH 1/5] [LoopInterchange] Don't consider loops with BTC=0
Do not consider loops with a zero backedge taken count as candidates for
interchange. This seems like a sensible thing to do to me, because it
suggests the loop doesn't execute and there is no point in
interchanging.
This avoids triggering an assert about phis and their uses. I have a
feeling that this fix might be hiding the issue, but I haven't yet been
able to trigger the assert with other test cases; every time the loops
are rejected for other reasons.
Since I think this is a self-contained improvement that avoids a lot
of test failures, I propose to reject this loops while I investigate
further if I can still trigger this in some way.
(Partial) fix for #163954
---
llvm/lib/Transforms/Scalar/LoopInterchange.cpp | 13 +++++++++++++
.../LoopInterchange/interchanged-loop-nest-4.ll | 2 +-
.../LoopInterchange/lcssa-phi-outer-latch.ll | 2 +-
.../LoopInterchange/pr43176-move-to-new-latch.ll | 2 +-
llvm/test/Transforms/LoopInterchange/pr43326.ll | 2 +-
llvm/test/Transforms/LoopInterchange/pr57148.ll | 2 +-
.../reductions-across-inner-and-outer-loop.ll | 2 +-
7 files changed, 19 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index 9aaf6a5aa4d6a..776560e678d8e 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -101,6 +101,12 @@ static cl::opt<unsigned int> MaxLoopNestDepth(
"loop-interchange-max-loop-nest-depth", cl::init(10), cl::Hidden,
cl::desc("Maximum depth of loop nest considered for the transform"));
+// This is mainly for testing purposes, and certain tests that rely on
+// behaviour that is more difficult to trigger otherwise.
+static cl::opt<bool> SkipLoopsWithZeroBTC(
+ "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
+ cl::desc("Do not consider loops with a backedge taken count of 0"));
+
// We prefer cache cost to vectorization by default.
static cl::list<RuleTy> Profitabilities(
"loop-interchange-profitabilities", cl::ZeroOrMore,
@@ -428,6 +434,13 @@ static bool isComputableLoopNest(ScalarEvolution *SE,
LLVM_DEBUG(dbgs() << "Couldn't compute backedge count\n");
return false;
}
+ // A loop with a backedge that isn't taken, e.g. an unconditional branch
+ // true, isn't really a loop and we don't want to consider it as a
+ // candidate.
+ if (ExitCountOuter && SkipLoopsWithZeroBTC && ExitCountOuter->isZero()) {
+ LLVM_DEBUG(dbgs() << "Single iteration loop\n");
+ return false;
+ }
if (L->getNumBackEdges() != 1) {
LLVM_DEBUG(dbgs() << "NumBackEdges is not equal to 1\n");
return false;
diff --git a/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll b/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
index f61054409937c..bbd554c8e47fb 100644
--- a/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
+++ b/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
@@ -1,5 +1,5 @@
; REQUIRES: asserts
-; RUN: opt < %s -passes="loop(loop-interchange,loop-interchange)" -cache-line-size=8 -verify-dom-info -verify-loop-info \
+; RUN: opt < %s -passes="loop(loop-interchange,loop-interchange)" -cache-line-size=8 -verify-dom-info -verify-loop-info -loop-interchange-skip-zero-btc=false \
; RUN: -debug-only=loop-interchange 2>&1 | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
diff --git a/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll b/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll
index 92ce3288b4529..1a1780addb708 100644
--- a/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll
+++ b/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
-; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
+; RUN: opt < %s -passes=loop-interchange -loop-interchange-skip-zero-btc=false -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
; This test is checking that blocks outer.body and outer.latch, where outer.body is the exit
; block of the inner loop and outer.latch the latch of the outer loop, correctly
diff --git a/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll b/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll
index f02ee1a0ced19..8968350c51788 100644
--- a/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S
+; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -loop-interchange-skip-zero-btc=false -S
; RUN: FileCheck --input-file=%t %s
@b = external dso_local global [5 x i32], align 16
diff --git a/llvm/test/Transforms/LoopInterchange/pr43326.ll b/llvm/test/Transforms/LoopInterchange/pr43326.ll
index cc4f07c722dd9..f75d377755ab7 100644
--- a/llvm/test/Transforms/LoopInterchange/pr43326.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr43326.ll
@@ -1,5 +1,5 @@
; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S \
-; RUN: -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1
+; RUN: -loop-interchange-skip-zero-btc=false -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1
; RUN: FileCheck --input-file=%t --check-prefix=REMARKS %s
@a = global i32 0
diff --git a/llvm/test/Transforms/LoopInterchange/pr57148.ll b/llvm/test/Transforms/LoopInterchange/pr57148.ll
index 747dbbcb4a44e..06dbc97efa3aa 100644
--- a/llvm/test/Transforms/LoopInterchange/pr57148.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr57148.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=loop-interchange -cache-line-size=4 -loop-interchange-threshold=-100 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
+; RUN: opt < %s -passes=loop-interchange -loop-interchange-skip-zero-btc=false -cache-line-size=4 -loop-interchange-threshold=-100 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
; Make sure the loops are in LCSSA form after loop interchange,
; and loop interchange does not hit assertion errors and crash.
diff --git a/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll b/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
index 51fda4cf1ebe1..af9e5f7e58bc4 100644
--- a/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
+++ b/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
@@ -1,5 +1,5 @@
; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S \
-; RUN: -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1 | FileCheck %s
+; RUN: -loop-interchange-skip-zero-btc=false -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1 | FileCheck %s
; RUN: FileCheck --input-file=%t --check-prefix=REMARKS %s
>From f51d9f643a8f8a5012c1691f4fb129df759707a3 Mon Sep 17 00:00:00 2001
From: Sjoerd Meijer <smeijer at nvidia.com>
Date: Sat, 8 Nov 2025 01:26:23 -0800
Subject: [PATCH 2/5] Forgto to add test-case
---
.../Transforms/LoopInterchange/zero-btc.ll | 56 +++++++++++++++++++
1 file changed, 56 insertions(+)
create mode 100644 llvm/test/Transforms/LoopInterchange/zero-btc.ll
diff --git a/llvm/test/Transforms/LoopInterchange/zero-btc.ll b/llvm/test/Transforms/LoopInterchange/zero-btc.ll
new file mode 100644
index 0000000000000..58d794e5def40
--- /dev/null
+++ b/llvm/test/Transforms/LoopInterchange/zero-btc.ll
@@ -0,0 +1,56 @@
+; 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 -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
+
+; Test case for issue: https://github.com/llvm/llvm-project/issues/163954
+
+define void @test() {
+; CHECK-LABEL: define void @test() {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: br label %[[OUTER_HEADER:.*]]
+; CHECK: [[OUTER_HEADER]]:
+; CHECK-NEXT: [[I:%.*]] = phi i8 [ 0, %[[ENTRY]] ], [ [[DOTLCSSA:%.*]], %[[OUTER_LATCH:.*]] ]
+; CHECK-NEXT: br label %[[INNER_HEADER:.*]]
+; CHECK: [[INNER_HEADER]]:
+; CHECK-NEXT: [[J:%.*]] = phi i64 [ 0, %[[OUTER_HEADER]] ], [ [[J_NEXT:%.*]], %[[INNER_LATCH:.*]] ]
+; CHECK-NEXT: [[TMP0:%.*]] = phi i8 [ [[I]], %[[OUTER_HEADER]] ], [ [[TMP1:%.*]], %[[INNER_LATCH]] ]
+; CHECK-NEXT: br label %[[INNER_BODY:.*]]
+; CHECK: [[INNER_BODY]]:
+; CHECK-NEXT: br i1 true, label %[[INNER_LATCH]], label %[[INNER_BODY]]
+; CHECK: [[INNER_LATCH]]:
+; CHECK-NEXT: [[TMP1]] = or i8 [[TMP0]], 0
+; CHECK-NEXT: [[J_NEXT]] = add i64 [[J]], 1
+; CHECK-NEXT: br i1 true, label %[[OUTER_LATCH]], label %[[INNER_HEADER]]
+; CHECK: [[OUTER_LATCH]]:
+; CHECK-NEXT: [[DOTLCSSA]] = phi i8 [ [[TMP1]], %[[INNER_LATCH]] ]
+; CHECK-NEXT: br i1 true, label %[[EXIT:.*]], label %[[OUTER_HEADER]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: ret void
+;
+entry:
+ br label %outer.header
+
+outer.header:
+ %i = phi i8 [ 0, %entry ], [ %1, %outer.latch ]
+ br label %inner.header
+
+inner.header:
+ %j = phi i64 [ 0, %outer.header ], [ %j.next, %inner.latch ]
+ %0 = phi i8 [ %i, %outer.header ], [ %1, %inner.latch ]
+ br label %inner.body
+
+inner.body:
+ br i1 true, label %inner.latch, label %inner.body ; another (self) loop, but never taken
+
+inner.latch:
+ %1 = or i8 %0, 0
+ %j.next = add i64 %j, 1
+ br i1 true, label %outer.latch, label %inner.header
+
+outer.latch:
+ br i1 true, label %exit, label %outer.header
+
+exit:
+ ret void
+}
>From e3abad5993e222c6f2f8bdc674478f76cced67bc Mon Sep 17 00:00:00 2001
From: Sjoerd Meijer <smeijer at nvidia.com>
Date: Mon, 10 Nov 2025 03:44:40 -0800
Subject: [PATCH 3/5] Removed datalayout from test, improved debug message, and
clarified comment.
---
llvm/lib/Transforms/Scalar/LoopInterchange.cpp | 16 +++++++++-------
llvm/test/Transforms/LoopInterchange/zero-btc.ll | 2 --
2 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index 776560e678d8e..353de3aacd4be 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -101,12 +101,6 @@ static cl::opt<unsigned int> MaxLoopNestDepth(
"loop-interchange-max-loop-nest-depth", cl::init(10), cl::Hidden,
cl::desc("Maximum depth of loop nest considered for the transform"));
-// This is mainly for testing purposes, and certain tests that rely on
-// behaviour that is more difficult to trigger otherwise.
-static cl::opt<bool> SkipLoopsWithZeroBTC(
- "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
- cl::desc("Do not consider loops with a backedge taken count of 0"));
-
// We prefer cache cost to vectorization by default.
static cl::list<RuleTy> Profitabilities(
"loop-interchange-profitabilities", cl::ZeroOrMore,
@@ -126,6 +120,13 @@ static cl::list<RuleTy> Profitabilities(
"Ignore profitability, force interchange (does not "
"work with other options)")));
+// FIXME: this option exists mainly for a couple of tests that check some
+// corner cases that is more difficult to trigger otherwise; these tests should
+// be rewritten and this option removed if possible.
+static cl::opt<bool> SkipLoopsWithZeroBTC(
+ "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
+ cl::desc("Do not consider loops with a backedge taken count of 0"));
+
#ifndef NDEBUG
static bool noDuplicateRulesAndIgnore(ArrayRef<RuleTy> Rules) {
SmallSet<RuleTy, 4> Set;
@@ -438,7 +439,8 @@ static bool isComputableLoopNest(ScalarEvolution *SE,
// true, isn't really a loop and we don't want to consider it as a
// candidate.
if (ExitCountOuter && SkipLoopsWithZeroBTC && ExitCountOuter->isZero()) {
- LLVM_DEBUG(dbgs() << "Single iteration loop\n");
+ LLVM_DEBUG(dbgs() << "The loop back-edge isn't taken, rejecting single "
+ "iteration loop\n");
return false;
}
if (L->getNumBackEdges() != 1) {
diff --git a/llvm/test/Transforms/LoopInterchange/zero-btc.ll b/llvm/test/Transforms/LoopInterchange/zero-btc.ll
index 58d794e5def40..af2aa72adcb94 100644
--- a/llvm/test/Transforms/LoopInterchange/zero-btc.ll
+++ b/llvm/test/Transforms/LoopInterchange/zero-btc.ll
@@ -1,8 +1,6 @@
; 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 -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
-target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
-
; Test case for issue: https://github.com/llvm/llvm-project/issues/163954
define void @test() {
>From 5d9326ab1c456f970153427a0418358a07170d5c Mon Sep 17 00:00:00 2001
From: Sjoerd Meijer <smeijer at nvidia.com>
Date: Sat, 15 Nov 2025 01:00:08 -0800
Subject: [PATCH 4/5] TMP
---
llvm/lib/Transforms/Scalar/LoopInterchange.cpp | 9 +++++----
.../LoopInterchange/interchanged-loop-nest-4.ll | 2 +-
.../Transforms/LoopInterchange/lcssa-phi-outer-latch.ll | 2 +-
.../LoopInterchange/pr43176-move-to-new-latch.ll | 2 +-
llvm/test/Transforms/LoopInterchange/pr43326.ll | 2 +-
5 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index 353de3aacd4be..0b01f05f65866 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -123,9 +123,9 @@ static cl::list<RuleTy> Profitabilities(
// FIXME: this option exists mainly for a couple of tests that check some
// corner cases that is more difficult to trigger otherwise; these tests should
// be rewritten and this option removed if possible.
-static cl::opt<bool> SkipLoopsWithZeroBTC(
- "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
- cl::desc("Do not consider loops with a backedge taken count of 0"));
+//static cl::opt<bool> SkipLoopsWithZeroBTC(
+// "loop-interchange-skip-zero-btc", cl::init(true), cl::Hidden,
+// cl::desc("Do not consider loops with a backedge taken count of 0"));
#ifndef NDEBUG
static bool noDuplicateRulesAndIgnore(ArrayRef<RuleTy> Rules) {
@@ -438,9 +438,10 @@ static bool isComputableLoopNest(ScalarEvolution *SE,
// A loop with a backedge that isn't taken, e.g. an unconditional branch
// true, isn't really a loop and we don't want to consider it as a
// candidate.
- if (ExitCountOuter && SkipLoopsWithZeroBTC && ExitCountOuter->isZero()) {
+ if (ExitCountOuter && /*SkipLoopsWithZeroBTC && */ExitCountOuter->isZero()) {
LLVM_DEBUG(dbgs() << "The loop back-edge isn't taken, rejecting single "
"iteration loop\n");
+ LLVM_DEBUG(L->dump());
return false;
}
if (L->getNumBackEdges() != 1) {
diff --git a/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll b/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
index bbd554c8e47fb..f61054409937c 100644
--- a/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
+++ b/llvm/test/Transforms/LoopInterchange/interchanged-loop-nest-4.ll
@@ -1,5 +1,5 @@
; REQUIRES: asserts
-; RUN: opt < %s -passes="loop(loop-interchange,loop-interchange)" -cache-line-size=8 -verify-dom-info -verify-loop-info -loop-interchange-skip-zero-btc=false \
+; RUN: opt < %s -passes="loop(loop-interchange,loop-interchange)" -cache-line-size=8 -verify-dom-info -verify-loop-info \
; RUN: -debug-only=loop-interchange 2>&1 | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
diff --git a/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll b/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll
index 1a1780addb708..92ce3288b4529 100644
--- a/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll
+++ b/llvm/test/Transforms/LoopInterchange/lcssa-phi-outer-latch.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
-; RUN: opt < %s -passes=loop-interchange -loop-interchange-skip-zero-btc=false -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
+; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
; This test is checking that blocks outer.body and outer.latch, where outer.body is the exit
; block of the inner loop and outer.latch the latch of the outer loop, correctly
diff --git a/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll b/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll
index 8968350c51788..f02ee1a0ced19 100644
--- a/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr43176-move-to-new-latch.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -loop-interchange-skip-zero-btc=false -S
+; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S
; RUN: FileCheck --input-file=%t %s
@b = external dso_local global [5 x i32], align 16
diff --git a/llvm/test/Transforms/LoopInterchange/pr43326.ll b/llvm/test/Transforms/LoopInterchange/pr43326.ll
index f75d377755ab7..cc4f07c722dd9 100644
--- a/llvm/test/Transforms/LoopInterchange/pr43326.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr43326.ll
@@ -1,5 +1,5 @@
; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S \
-; RUN: -loop-interchange-skip-zero-btc=false -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1
+; RUN: -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1
; RUN: FileCheck --input-file=%t --check-prefix=REMARKS %s
@a = global i32 0
>From 56c3e9b1fc069e94ce7b7e57eb5f423e62f066a1 Mon Sep 17 00:00:00 2001
From: Sjoerd Meijer <smeijer at nvidia.com>
Date: Mon, 17 Nov 2025 09:36:00 -0800
Subject: [PATCH 5/5] Don't reject the whole loopnest, fixed up and added test
case.
---
.../lib/Transforms/Scalar/LoopInterchange.cpp | 60 +++++++++----
.../loopnest-with-outer-btc0.ll | 73 ++++++++++++++++
.../Transforms/LoopInterchange/pr43326.ll | 6 +-
.../Transforms/LoopInterchange/pr57148.ll | 84 +++++++++++--------
.../reductions-across-inner-and-outer-loop.ll | 2 +-
5 files changed, 168 insertions(+), 57 deletions(-)
create mode 100644 llvm/test/Transforms/LoopInterchange/loopnest-with-outer-btc0.ll
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index 0b01f05f65866..9b93339e1bedc 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -46,6 +46,7 @@
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <cassert>
+#include <map>
#include <utility>
#include <vector>
@@ -428,22 +429,15 @@ static bool hasSupportedLoopDepth(ArrayRef<Loop *> LoopList,
}
static bool isComputableLoopNest(ScalarEvolution *SE,
- ArrayRef<Loop *> LoopList) {
+ ArrayRef<Loop *> LoopList,
+ std::map<const Loop *, const SCEV *> &LoopBTC) {
for (Loop *L : LoopList) {
const SCEV *ExitCountOuter = SE->getBackedgeTakenCount(L);
+ LoopBTC[L] = ExitCountOuter;
if (isa<SCEVCouldNotCompute>(ExitCountOuter)) {
LLVM_DEBUG(dbgs() << "Couldn't compute backedge count\n");
return false;
}
- // A loop with a backedge that isn't taken, e.g. an unconditional branch
- // true, isn't really a loop and we don't want to consider it as a
- // candidate.
- if (ExitCountOuter && /*SkipLoopsWithZeroBTC && */ExitCountOuter->isZero()) {
- LLVM_DEBUG(dbgs() << "The loop back-edge isn't taken, rejecting single "
- "iteration loop\n");
- LLVM_DEBUG(L->dump());
- return false;
- }
if (L->getNumBackEdges() != 1) {
LLVM_DEBUG(dbgs() << "NumBackEdges is not equal to 1\n");
return false;
@@ -561,7 +555,8 @@ class LoopInterchangeProfitability {
/// Check if the loop interchange is profitable.
bool isProfitable(const Loop *InnerLoop, const Loop *OuterLoop,
unsigned InnerLoopId, unsigned OuterLoopId,
- CharMatrix &DepMatrix, CacheCostManager &CCM);
+ CharMatrix &DepMatrix, CacheCostManager &CCM,
+ std::map<const Loop *, const SCEV *> &LoopBTC);
private:
int getInstrOrderCost();
@@ -618,14 +613,17 @@ struct LoopInterchange {
DependenceInfo *DI = nullptr;
DominatorTree *DT = nullptr;
LoopStandardAnalysisResults *AR = nullptr;
-
/// Interface to emit optimization remarks.
OptimizationRemarkEmitter *ORE;
+ // A cache to avoid recalculating the backedge-taken count for a loop.
+ std::map<const Loop *, const SCEV *> LoopBTC;
LoopInterchange(ScalarEvolution *SE, LoopInfo *LI, DependenceInfo *DI,
DominatorTree *DT, LoopStandardAnalysisResults *AR,
- OptimizationRemarkEmitter *ORE)
- : SE(SE), LI(LI), DI(DI), DT(DT), AR(AR), ORE(ORE) {}
+ OptimizationRemarkEmitter *ORE,
+ std::map<const Loop *, const SCEV *> &&LoopBTC)
+ : SE(SE), LI(LI), DI(DI), DT(DT), AR(AR), ORE(ORE),
+ LoopBTC(std::move(LoopBTC)) {}
bool run(Loop *L) {
if (L->getParentLoop())
@@ -717,7 +715,7 @@ struct LoopInterchange {
LLVM_DEBUG(dbgs() << "Loops are legal to interchange\n");
LoopInterchangeProfitability LIP(OuterLoop, InnerLoop, SE, ORE);
if (!LIP.isProfitable(InnerLoop, OuterLoop, InnerLoopId, OuterLoopId,
- DependencyMatrix, CCM)) {
+ DependencyMatrix, CCM, LoopBTC)) {
LLVM_DEBUG(dbgs() << "Interchanging loops not profitable.\n");
return false;
}
@@ -1477,7 +1475,30 @@ std::optional<bool> LoopInterchangeProfitability::isProfitableForVectorization(
bool LoopInterchangeProfitability::isProfitable(
const Loop *InnerLoop, const Loop *OuterLoop, unsigned InnerLoopId,
- unsigned OuterLoopId, CharMatrix &DepMatrix, CacheCostManager &CCM) {
+ unsigned OuterLoopId, CharMatrix &DepMatrix, CacheCostManager &CCM,
+ std::map<const Loop *, const SCEV *> &LoopBTC) {
+
+ auto *InnerBTC = LoopBTC[InnerLoop];
+ auto *OuterBTC = LoopBTC[OuterLoop];
+ assert(InnerBTC && OuterBTC &&
+ "Loop BTC should exist in cache but not found");
+ // A loop with a backedge that isn't taken, e.g. an unconditional branch
+ // true, isn't really a loop and we don't want to consider it as a
+ // candidate.
+ // TODO: when interchange is forced, we should probably also allow
+ // interchange for these loops, and thus this logic should be moved just
+ // below the cost-model ignore check below. But this check is done first
+ // to avoid the issue in #163954.
+ if (InnerBTC && InnerBTC->isZero()) {
+ LLVM_DEBUG(dbgs() << "Inner loop back-edge isn't taken, rejecting "
+ "single iteration loop\n");
+ return false;
+ }
+ if (OuterBTC && OuterBTC->isZero()) {
+ LLVM_DEBUG(dbgs() << "Outer loop back-edge isn't taken, rejecting "
+ "single iteration loop\n");
+ return false;
+ }
// Return true if interchange is forced and the cost-model ignored.
if (Profitabilities.size() == 1 && Profitabilities[0] == RuleTy::Ignore)
@@ -2114,6 +2135,7 @@ PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
LPMUpdater &U) {
Function &F = *LN.getParent();
SmallVector<Loop *, 8> LoopList(LN.getLoops());
+ std::map<const Loop *, const SCEV *> LoopBTC;
if (MaxMemInstrCount < 1) {
LLVM_DEBUG(dbgs() << "MaxMemInstrCount should be at least 1");
@@ -2125,7 +2147,7 @@ PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
if (!hasSupportedLoopDepth(LoopList, ORE))
return PreservedAnalyses::all();
// Ensure computable loop nest.
- if (!isComputableLoopNest(&AR.SE, LoopList)) {
+ if (!isComputableLoopNest(&AR.SE, LoopList, LoopBTC)) {
LLVM_DEBUG(dbgs() << "Not valid loop candidate for interchange\n");
return PreservedAnalyses::all();
}
@@ -2138,7 +2160,9 @@ PreservedAnalyses LoopInterchangePass::run(LoopNest &LN,
});
DependenceInfo DI(&F, &AR.AA, &AR.SE, &AR.LI);
- if (!LoopInterchange(&AR.SE, &AR.LI, &DI, &AR.DT, &AR, &ORE).run(LN))
+ if (!LoopInterchange(&AR.SE, &AR.LI, &DI, &AR.DT, &AR, &ORE,
+ std::move(LoopBTC))
+ .run(LN))
return PreservedAnalyses::all();
U.markLoopNestChanged(true);
return getLoopPassPreservedAnalyses();
diff --git a/llvm/test/Transforms/LoopInterchange/loopnest-with-outer-btc0.ll b/llvm/test/Transforms/LoopInterchange/loopnest-with-outer-btc0.ll
new file mode 100644
index 0000000000000..ac3bbcf0511ef
--- /dev/null
+++ b/llvm/test/Transforms/LoopInterchange/loopnest-with-outer-btc0.ll
@@ -0,0 +1,73 @@
+; RUN: opt < %s -passes=loop-interchange -verify-dom-info -verify-loop-info \
+; RUN: -pass-remarks-output=%t -pass-remarks='loop-interchange' -S
+; RUN: cat %t | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+ at D = common global [100 x [100 x [100 x i32]]] zeroinitializer
+
+; Test for interchange in
+;
+; for(int i=0;i<1;i++)
+; for(int j=0;j<100;j++)
+; for(int k=0;k<100;k++)
+; D[i][k][j] = D[i][k][j]+t;
+;
+
+; CHECK: --- !Analysis
+; CHECK-NEXT: Pass: loop-interchange
+; CHECK-NEXT: Name: Dependence
+; CHECK-NEXT: Function: interchange_i_and_j
+; CHECK-NEXT: Args:
+; CHECK-NEXT: - String: Computed dependence info, invoking the transform.
+; CHECK-NEXT: ...
+; CHECK-NEXT: --- !Passed
+; CHECK-NEXT: Pass: loop-interchange
+; CHECK-NEXT: Name: Interchanged
+; CHECK-NEXT: Function: interchange_i_and_j
+; CHECK-NEXT: Args:
+; CHECK-NEXT: - String: Loop interchanged with enclosing loop.
+; CHECK-NEXT: ...
+; CHECK-NEXT: --- !Missed
+; CHECK-NEXT: Pass: loop-interchange
+; CHECK-NEXT: Name: InterchangeNotProfitable
+; CHECK-NEXT: Function: interchange_i_and_j
+; CHECK-NEXT: Args:
+; CHECK-NEXT: - String: Insufficient information to calculate the cost of loop for interchange.
+; CHECK-NEXT: ...
+
+define void @interchange_i_and_j(i32 %t){
+entry:
+ br label %outer.header
+
+outer.header:
+ %i = phi i64 [ 0, %entry ], [ %inc16, %for.inc15 ]
+ br label %inner1.header
+
+inner1.header:
+ %j = phi i64 [ 0, %outer.header ], [ %inc13, %for.inc12 ]
+ br label %inner2.body
+
+inner2.body:
+ %k = phi i64 [ 0, %inner1.header ], [ %inc, %inner2.body ]
+ %arrayidx8 = getelementptr inbounds [100 x [100 x [100 x i32]]], ptr @D, i64 0, i64 %i, i64 %k, i64 %j
+ %0 = load i32, ptr %arrayidx8
+ %add = add nsw i32 %0, %t
+ store i32 %add, ptr %arrayidx8
+ %inc = add nuw nsw i64 %k, 1
+ %exitcond = icmp eq i64 %inc, 100
+ br i1 %exitcond, label %for.inc12, label %inner2.body
+
+for.inc12:
+ %inc13 = add nuw nsw i64 %j, 1
+ %exitcond29 = icmp eq i64 %inc13, 100
+ br i1 %exitcond29, label %for.inc15, label %inner1.header
+
+for.inc15:
+ %inc16 = add nuw nsw i64 %i, 1
+ %exitcond30 = icmp eq i64 %inc16, 1
+ br i1 %exitcond30, label %for.end17, label %outer.header
+
+for.end17:
+ ret void
+}
diff --git a/llvm/test/Transforms/LoopInterchange/pr43326.ll b/llvm/test/Transforms/LoopInterchange/pr43326.ll
index cc4f07c722dd9..666f11d4969a0 100644
--- a/llvm/test/Transforms/LoopInterchange/pr43326.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr43326.ll
@@ -64,7 +64,7 @@ for.end: ; preds = %for.inc
for.inc10: ; preds = %for.end
%j.next = add i8 %j, -1
- %cmp = icmp sgt i8 %j.next, -1
+ %cmp = icmp sgt i8 %j.next, -10
br i1 %cmp, label %inner1.header, label %for.end11
for.end11: ; preds = %for.inc10
@@ -75,8 +75,8 @@ for.end11: ; preds = %for.inc10
for.inc12: ; preds = %for.end11
%inc13 = add nsw i32 %inc1312, 1
- %tobool.not = icmp eq i32 %inc13, 0
- br i1 %tobool.not, label %for.cond.for.end14_crit_edge, label %outer.header
+ %tobool.not = icmp slt i32 %inc13, 42
+ br i1 %tobool.not, label %outer.header, label %for.cond.for.end14_crit_edge
for.cond.for.end14_crit_edge: ; preds = %for.inc12
%inc13.lcssa = phi i32 [ %inc13, %for.inc12 ]
diff --git a/llvm/test/Transforms/LoopInterchange/pr57148.ll b/llvm/test/Transforms/LoopInterchange/pr57148.ll
index 06dbc97efa3aa..b5b1c0e265013 100644
--- a/llvm/test/Transforms/LoopInterchange/pr57148.ll
+++ b/llvm/test/Transforms/LoopInterchange/pr57148.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=loop-interchange -loop-interchange-skip-zero-btc=false -cache-line-size=4 -loop-interchange-threshold=-100 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
+; RUN: opt < %s -passes=loop-interchange -cache-line-size=4 -loop-interchange-threshold=-100 -verify-dom-info -verify-loop-info -verify-scev -verify-loop-lcssa -S | FileCheck %s
; Make sure the loops are in LCSSA form after loop interchange,
; and loop interchange does not hit assertion errors and crash.
@@ -35,16 +35,19 @@ define void @test1() {
; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[ARRAYIDX55]], align 1
; CHECK-NEXT: [[ADD61:%.*]] = add i32 undef, undef
; CHECK-NEXT: [[INC63:%.*]] = add nsw i16 [[K_09]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[K_09]], 42
; CHECK-NEXT: br label [[FOR_END67]]
; CHECK: for.body42.split:
; CHECK-NEXT: [[ADD61_LCSSA:%.*]] = phi i32 [ [[ADD61]], [[FOR_END67]] ]
; CHECK-NEXT: [[TMP1]] = add nsw i16 [[K_09]], 1
-; CHECK-NEXT: br i1 true, label [[FOR_END64]], label [[FOR_BODY42]]
+; CHECK-NEXT: [[TMP2:%.*]] = icmp slt i16 [[K_09]], 42
+; CHECK-NEXT: br i1 [[TMP2]], label [[FOR_BODY42]], label [[FOR_END64]]
; CHECK: for.end64:
; CHECK-NEXT: [[ADD61_LCSSA_LCSSA:%.*]] = phi i32 [ [[ADD61_LCSSA]], [[FOR_BODY42_SPLIT]] ]
; CHECK-NEXT: store i32 [[ADD61_LCSSA_LCSSA]], ptr undef, align 1
; CHECK-NEXT: [[INC66]] = add nuw nsw i16 [[J_010]], 1
-; CHECK-NEXT: br i1 true, label [[FOR_COND75_PREHEADER:%.*]], label [[FOR_COND37_PREHEADER]]
+; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i16 [[J_010]], 43
+; CHECK-NEXT: br i1 [[CMP2]], label [[FOR_COND37_PREHEADER]], label [[FOR_COND75_PREHEADER:%.*]]
; CHECK: for.end67:
; CHECK-NEXT: [[INC69]] = add nuw nsw i16 [[I_011]], 1
; CHECK-NEXT: [[EXITCOND13_NOT:%.*]] = icmp eq i16 [[INC69]], 2
@@ -72,12 +75,14 @@ for.body42: ; preds = %for.body42, %for.co
%0 = load i32, ptr %arrayidx55, align 1
%add61 = add i32 undef, undef
%inc63 = add nsw i16 %k.09, 1
- br i1 true, label %for.end64, label %for.body42
+ %cmp = icmp slt i16 %k.09, 42
+ br i1 %cmp, label %for.body42, label %for.end64
for.end64: ; preds = %for.body42
store i32 %add61, ptr undef, align 1
%inc66 = add nuw nsw i16 %j.010, 1
- br i1 true, label %for.end67, label %for.cond37.preheader
+ %cmp2 = icmp slt i16 %j.010, 43
+ br i1 %cmp2, label %for.cond37.preheader, label %for.end67
for.end67: ; preds = %for.end64
%inc69 = add nuw nsw i16 %i.011, 1
@@ -88,7 +93,6 @@ for.cond75: ; preds = %for.cond75, %for.en
br label %for.cond75
}
-
; Make sure that we split the phi nodes in the middle loop header
; into a separate basic block to avoid the situation where use of
; the outermost indvar appears before its def after interchanging
@@ -98,40 +102,42 @@ for.cond75: ; preds = %for.cond75, %for.en
define void @test2() {
; CHECK-LABEL: @test2(
; CHECK-NEXT: entry:
-; CHECK-NEXT: br label [[FOR_COND37_PREHEADER_PREHEADER:%.*]]
-; CHECK: for.cond33.preheader.preheader:
; CHECK-NEXT: br label [[FOR_COND33_PREHEADER:%.*]]
+; CHECK: for.cond33.preheader.preheader:
+; CHECK-NEXT: br label [[FOR_COND33_PREHEADER1:%.*]]
; CHECK: for.cond33.preheader:
; CHECK-NEXT: [[I_166:%.*]] = phi i16 [ [[INC69:%.*]], [[FOR_INC68:%.*]] ], [ 0, [[FOR_COND33_PREHEADER_PREHEADER:%.*]] ]
; CHECK-NEXT: [[ARRAYIDX60:%.*]] = getelementptr inbounds [2 x [4 x i32]], ptr @c, i16 0, i16 [[I_166]], i16 [[J_165:%.*]]
-; CHECK-NEXT: br label [[VECTOR_BODY85_SPLIT1:%.*]]
-; CHECK: for.cond37.preheader.preheader:
; CHECK-NEXT: br label [[FOR_COND37_PREHEADER:%.*]]
+; CHECK: for.cond37.preheader.preheader:
+; CHECK-NEXT: br label [[FOR_COND37_PREHEADER1:%.*]]
; CHECK: for.cond37.preheader:
-; CHECK-NEXT: [[J_165]] = phi i16 [ [[INC66:%.*]], [[MIDDLE_BLOCK80:%.*]] ], [ 0, [[FOR_COND37_PREHEADER_PREHEADER]] ]
-; CHECK-NEXT: br label [[FOR_COND37_PREHEADER_SPLIT:%.*]]
-; CHECK: for.cond37.preheader.split:
+; CHECK-NEXT: [[J_165]] = phi i16 [ [[INC66:%.*]], [[MIDDLE_BLOCK80:%.*]] ], [ 0, [[FOR_COND33_PREHEADER]] ]
; CHECK-NEXT: br label [[VECTOR_BODY85:%.*]]
+; CHECK: for.cond37.preheader.split:
+; CHECK-NEXT: br label [[VECTOR_BODY86:%.*]]
; CHECK: vector.body85:
-; CHECK-NEXT: [[INDEX86:%.*]] = phi i16 [ 0, [[FOR_COND37_PREHEADER_SPLIT]] ], [ [[TMP3:%.*]], [[VECTOR_BODY85_SPLIT:%.*]] ]
+; CHECK-NEXT: [[INDEX86:%.*]] = phi i16 [ 0, [[VECTOR_BODY85]] ], [ [[TMP5:%.*]], [[VECTOR_BODY85_SPLIT:%.*]] ]
; CHECK-NEXT: br label [[FOR_COND33_PREHEADER_PREHEADER]]
; CHECK: vector.body85.split1:
; CHECK-NEXT: [[TMP0:%.*]] = or disjoint i16 [[INDEX86]], 2
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds [512 x [4 x i32]], ptr @b, i16 0, i16 [[TMP0]], i16 [[J_165]]
; CHECK-NEXT: [[TMP2:%.*]] = load i32, ptr [[TMP1]], align 1
-; CHECK-NEXT: [[INDEX_NEXT87:%.*]] = add nuw i16 [[INDEX86]], 4
+; CHECK-NEXT: [[TMP3:%.*]] = add nuw i16 [[INDEX86]], 4
+; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i16 [[INDEX86]], 42
; CHECK-NEXT: br label [[FOR_INC68]]
; CHECK: vector.body85.split:
-; CHECK-NEXT: [[TMP3]] = add nuw i16 [[INDEX86]], 4
-; CHECK-NEXT: br i1 true, label [[MIDDLE_BLOCK80]], label [[VECTOR_BODY85]]
+; CHECK-NEXT: [[TMP5]] = add nuw i16 [[INDEX86]], 4
+; CHECK-NEXT: [[TMP4:%.*]] = icmp slt i16 [[INDEX86]], 42
+; CHECK-NEXT: br i1 [[TMP4]], label [[VECTOR_BODY86]], label [[MIDDLE_BLOCK80]]
; CHECK: middle.block80:
; CHECK-NEXT: [[INC66]] = add nuw nsw i16 [[J_165]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[INC66]], 42
-; CHECK-NEXT: br i1 [[CMP]], label [[FOR_COND75_PREHEADER:%.*]], label [[FOR_COND37_PREHEADER]]
+; CHECK-NEXT: br i1 [[CMP]], label [[FOR_COND37_PREHEADER1]], label [[FOR_COND75_PREHEADER:%.*]]
; CHECK: for.inc68:
; CHECK-NEXT: [[INC69]] = add nuw nsw i16 [[I_166]], 1
-; CHECK-NEXT: [[EXITCOND77_NOT:%.*]] = icmp eq i16 [[INC69]], 2
-; CHECK-NEXT: br i1 [[EXITCOND77_NOT]], label [[VECTOR_BODY85_SPLIT]], label [[FOR_COND33_PREHEADER]]
+; CHECK-NEXT: [[EXITCOND77_NOT:%.*]] = icmp slt i16 [[INC69]], 24
+; CHECK-NEXT: br i1 [[EXITCOND77_NOT]], label [[FOR_COND33_PREHEADER1]], label [[VECTOR_BODY85_SPLIT]]
; CHECK: for.cond75.preheader:
; CHECK-NEXT: unreachable
;
@@ -153,17 +159,18 @@ vector.body85: ; preds = %vector.body85, %for
%1 = getelementptr inbounds [512 x [4 x i32]], ptr @b, i16 0, i16 %0, i16 %j.165
%2 = load i32, ptr %1, align 1
%index.next87 = add nuw i16 %index86, 4
- br i1 true, label %middle.block80, label %vector.body85
+ %cmp2 = icmp slt i16 %index86, 42
+ br i1 %cmp2, label %vector.body85, label %middle.block80
middle.block80: ; preds = %vector.body85
%inc66 = add nuw nsw i16 %j.165, 1
%cmp = icmp slt i16 %inc66, 42
- br i1 %cmp, label %for.inc68, label %for.cond37.preheader
+ br i1 %cmp, label %for.cond37.preheader, label %for.inc68
for.inc68: ; preds = %middle.block80
%inc69 = add nuw nsw i16 %i.166, 1
- %exitcond77.not = icmp eq i16 %inc69, 2
- br i1 %exitcond77.not, label %for.cond75.preheader, label %for.cond33.preheader
+ %exitcond77.not = icmp slt i16 %inc69, 24
+ br i1 %exitcond77.not, label %for.cond33.preheader, label %for.cond75.preheader
for.cond75.preheader: ; preds = %for.inc68
unreachable
@@ -178,11 +185,11 @@ define void @test3() {
; CHECK-NEXT: br label [[FOR_COND33_PREHEADER:%.*]]
; CHECK: for.cond33.preheader:
; CHECK-NEXT: [[I_011:%.*]] = phi i16 [ [[INC69:%.*]], [[FOR_END67:%.*]] ], [ 0, [[FOR_COND33_PREHEADER_PREHEADER:%.*]] ]
-; CHECK-NEXT: br label [[FOR_BODY42_SPLIT1:%.*]]
+; CHECK-NEXT: br label [[FOR_COND38_PREHEADER:%.*]]
; CHECK: for.body42.preheader:
; CHECK-NEXT: br label [[FOR_BODY42:%.*]]
; CHECK: for.cond38.preheader.preheader:
-; CHECK-NEXT: br label [[FOR_COND38_PREHEADER:%.*]]
+; CHECK-NEXT: br label [[FOR_COND38_PREHEADER1:%.*]]
; CHECK: for.cond37.preheader.preheader:
; CHECK-NEXT: br label [[FOR_COND37_PREHEADER:%.*]]
; CHECK: for.cond37.preheader:
@@ -192,27 +199,31 @@ define void @test3() {
; CHECK-NEXT: [[K_010:%.*]] = phi i16 [ [[INC67:%.*]], [[FOR_END65:%.*]] ], [ 0, [[FOR_COND38_PREHEADER_PREHEADER]] ]
; CHECK-NEXT: br label [[FOR_BODY42_PREHEADER:%.*]]
; CHECK: for.body42:
-; CHECK-NEXT: [[K_09:%.*]] = phi i16 [ [[TMP1:%.*]], [[FOR_BODY42_SPLIT:%.*]] ], [ -512, [[FOR_BODY42_PREHEADER]] ]
+; CHECK-NEXT: [[K_09:%.*]] = phi i16 [ [[TMP3:%.*]], [[FOR_BODY42_SPLIT:%.*]] ], [ -512, [[FOR_BODY42_PREHEADER]] ]
; CHECK-NEXT: br label [[FOR_COND33_PREHEADER_PREHEADER]]
; CHECK: for.body42.split1:
; CHECK-NEXT: [[SUB51:%.*]] = add nsw i16 [[K_09]], 512
; CHECK-NEXT: [[ARRAYIDX55:%.*]] = getelementptr inbounds [1024 x [512 x [4 x i32]]], ptr @d, i16 0, i16 [[SUB51]], i16 [[J_010]], i16 [[K_010]]
; CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[ARRAYIDX55]], align 1
; CHECK-NEXT: [[ADD61:%.*]] = add i32 undef, undef
-; CHECK-NEXT: [[INC63:%.*]] = add nsw i16 [[K_09]], 1
+; CHECK-NEXT: [[TMP1:%.*]] = add nsw i16 [[K_09]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[K_09]], 42
; CHECK-NEXT: br label [[FOR_END67]]
; CHECK: for.body42.split:
; CHECK-NEXT: [[ADD61_LCSSA:%.*]] = phi i32 [ [[ADD61]], [[FOR_END67]] ]
-; CHECK-NEXT: [[TMP1]] = add nsw i16 [[K_09]], 1
-; CHECK-NEXT: br i1 true, label [[FOR_END65]], label [[FOR_BODY42]]
+; CHECK-NEXT: [[TMP3]] = add nsw i16 [[K_09]], 1
+; CHECK-NEXT: [[TMP2:%.*]] = icmp slt i16 [[K_09]], 42
+; CHECK-NEXT: br i1 [[TMP2]], label [[FOR_BODY42]], label [[FOR_END65]]
; CHECK: for.end65:
; CHECK-NEXT: [[ADD61_LCSSA_LCSSA:%.*]] = phi i32 [ [[ADD61_LCSSA]], [[FOR_BODY42_SPLIT]] ]
; CHECK-NEXT: store i32 [[ADD61_LCSSA_LCSSA]], ptr undef, align 1
; CHECK-NEXT: [[INC67]] = add nuw nsw i16 [[K_010]], 1
-; CHECK-NEXT: br i1 true, label [[FOR_END64]], label [[FOR_COND38_PREHEADER]]
+; CHECK-NEXT: [[CMP3:%.*]] = icmp slt i16 [[K_010]], 44
+; CHECK-NEXT: br i1 [[CMP3]], label [[FOR_COND38_PREHEADER1]], label [[FOR_END64]]
; CHECK: for.end64:
; CHECK-NEXT: [[INC66]] = add nuw nsw i16 [[J_010]], 1
-; CHECK-NEXT: br i1 true, label [[FOR_COND75_PREHEADER:%.*]], label [[FOR_COND37_PREHEADER]]
+; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i16 [[J_010]], 43
+; CHECK-NEXT: br i1 [[CMP2]], label [[FOR_COND37_PREHEADER]], label [[FOR_COND75_PREHEADER:%.*]]
; CHECK: for.end67:
; CHECK-NEXT: [[INC69]] = add nuw nsw i16 [[I_011]], 1
; CHECK-NEXT: [[EXITCOND13_NOT:%.*]] = icmp eq i16 [[INC69]], 2
@@ -244,16 +255,19 @@ for.body42: ; preds = %for.body42, %for.co
%0 = load i32, ptr %arrayidx55, align 1
%add61 = add i32 undef, undef
%inc63 = add nsw i16 %k.09, 1
- br i1 true, label %for.end65, label %for.body42
+ %cmp = icmp slt i16 %k.09, 42
+ br i1 %cmp, label %for.body42, label %for.end65
for.end65: ; preds = %for.body42
store i32 %add61, ptr undef, align 1
%inc67 = add nuw nsw i16 %k.010, 1
- br i1 true, label %for.end64, label %for.cond38.preheader
+ %cmp3 = icmp slt i16 %k.010, 44
+ br i1 %cmp3, label %for.cond38.preheader, label %for.end64
for.end64: ; preds = %for.end65
%inc66 = add nuw nsw i16 %j.010, 1
- br i1 true, label %for.end67, label %for.cond37.preheader
+ %cmp2 = icmp slt i16 %j.010, 43
+ br i1 %cmp2, label %for.cond37.preheader, label %for.end67
for.end67: ; preds = %for.end64
%inc69 = add nuw nsw i16 %i.011, 1
diff --git a/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll b/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
index af9e5f7e58bc4..51fda4cf1ebe1 100644
--- a/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
+++ b/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
@@ -1,5 +1,5 @@
; RUN: opt < %s -passes=loop-interchange -cache-line-size=64 -pass-remarks-missed='loop-interchange' -pass-remarks-output=%t -S \
-; RUN: -loop-interchange-skip-zero-btc=false -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1 | FileCheck %s
+; RUN: -verify-dom-info -verify-loop-info -verify-loop-lcssa -stats 2>&1 | FileCheck %s
; RUN: FileCheck --input-file=%t --check-prefix=REMARKS %s
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