[llvm] [MachineSink] Check predecessor/successor relationship between two basic blocks involved in critical edge splitting (PR #98540)
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Fri Jul 12 11:48:08 PDT 2024
https://github.com/yozhu updated https://github.com/llvm/llvm-project/pull/98540
>From c230c574fc3c7f3ebd837cf04a8a3aba2abf67db Mon Sep 17 00:00:00 2001
From: YongKang Zhu <yongzhu at fb.com>
Date: Thu, 11 Jul 2024 13:17:43 -0700
Subject: [PATCH 1/3] [MachineSink] Only add sink candidate if toBB is a
successor of fromBB
---
llvm/lib/CodeGen/MachineSink.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index bbc5ab13a0cd3..4d8de6765273f 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -913,7 +913,7 @@ bool MachineSinking::isWorthBreakingCriticalEdge(
auto Res = CEMergeCandidates.try_emplace(Key, From);
// We wanted to sink the same register into the same block, consider it to
// be profitable.
- if (!Res.second) {
+ if (!Res.second && Res.first->second->isSuccessor(To)) {
// Return the source block that was previously held off.
DeferredFromBlock = Res.first->second;
return true;
>From 321c05138b4bdc4ba9faa0089233479b7b807a78 Mon Sep 17 00:00:00 2001
From: YongKang Zhu <yongzhu at fb.com>
Date: Fri, 12 Jul 2024 07:41:35 -0700
Subject: [PATCH 2/3] Move check to a more genetic place and add test
---
llvm/lib/CodeGen/MachineSink.cpp | 4 +--
.../CodeGen/X86/MachineSink-Issue98477.ll | 36 +++++++++++++++++++
2 files changed, 38 insertions(+), 2 deletions(-)
create mode 100644 llvm/test/CodeGen/X86/MachineSink-Issue98477.ll
diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 4d8de6765273f..57b71d1a26859 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -913,7 +913,7 @@ bool MachineSinking::isWorthBreakingCriticalEdge(
auto Res = CEMergeCandidates.try_emplace(Key, From);
// We wanted to sink the same register into the same block, consider it to
// be profitable.
- if (!Res.second && Res.first->second->isSuccessor(To)) {
+ if (!Res.second) {
// Return the source block that was previously held off.
DeferredFromBlock = Res.first->second;
return true;
@@ -959,7 +959,7 @@ bool MachineSinking::isLegalToBreakCriticalEdge(MachineInstr &MI,
MachineBasicBlock *ToBB,
bool BreakPHIEdge) {
// Avoid breaking back edge. From == To means backedge for single BB cycle.
- if (!SplitEdges || FromBB == ToBB)
+ if (!SplitEdges || FromBB == ToBB || !FromBB->isSuccessor(ToBB))
return false;
MachineCycle *FromCycle = CI->getCycle(FromBB);
diff --git a/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll b/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll
new file mode 100644
index 0000000000000..abc41341043c8
--- /dev/null
+++ b/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll
@@ -0,0 +1,36 @@
+; RUN: llc < %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @main(i1 %tobool.not, i32 %0) {
+entry:
+ br i1 %tobool.not, label %if.end13, label %j.preheader
+
+ j.preheader: ; preds = %if.end13, %entry
+ %h.0.ph = phi i32 [ 1, %entry ], [ 0, %if.end13 ]
+ br label %j
+
+ j: ; preds = %if.then4, %j.preheader
+ %1 = phi i32 [ %div2, %if.then4 ], [ 0, %j.preheader ]
+ %rem1 = srem i32 1, %0
+ %cmp = icmp slt i32 %1, 0
+ %or.cond = select i1 false, i1 true, i1 %cmp
+ br i1 %or.cond, label %if.then4, label %if.end9
+
+ if.then4: ; preds = %j
+ %div2 = sdiv i32 1, 0
+ %rem5 = srem i32 1, %h.0.ph
+ br i1 %tobool.not, label %if.end9, label %j
+
+ if.end9: ; preds = %if.then4, %j
+ %2 = phi i32 [ 0, %j ], [ %rem5, %if.then4 ]
+ %tobool10.not = icmp eq i32 %2, 0
+ br i1 %tobool10.not, label %if.end13, label %while.body.lr.ph
+
+ while.body.lr.ph: ; preds = %if.end9
+ ret i32 %rem1
+
+ if.end13: ; preds = %if.end9, %entry
+ br label %j.preheader
+}
>From 2094b486dd77f0f58a43757d304e6a77b6dd152a Mon Sep 17 00:00:00 2001
From: YongKang Zhu <yongzhu at fb.com>
Date: Fri, 12 Jul 2024 11:47:32 -0700
Subject: [PATCH 3/3] update test to call FileCheck for extra validation
---
.../CodeGen/X86/MachineSink-Issue98477.ll | 42 ++++++++++++++++++-
1 file changed, 41 insertions(+), 1 deletion(-)
diff --git a/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll b/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll
index abc41341043c8..4df32854cdae4 100644
--- a/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll
+++ b/llvm/test/CodeGen/X86/MachineSink-Issue98477.ll
@@ -1,9 +1,49 @@
-; RUN: llc < %s
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s | FileCheck %s
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define i32 @main(i1 %tobool.not, i32 %0) {
+; CHECK-LABEL: main:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: movl $1, %r8d
+; CHECK-NEXT: testb $1, %dil
+; CHECK-NEXT: jne .LBB0_8
+; CHECK-NEXT: .LBB0_1: # %j.preheader
+; CHECK-NEXT: xorl %r9d, %r9d
+; CHECK-NEXT: jmp .LBB0_2
+; CHECK-NEXT: .p2align 4, 0x90
+; CHECK-NEXT: .LBB0_5: # %if.then4
+; CHECK-NEXT: # in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT: movl $1, %eax
+; CHECK-NEXT: xorl %edx, %edx
+; CHECK-NEXT: divl %r8d
+; CHECK-NEXT: testb $1, %dil
+; CHECK-NEXT: jne .LBB0_6
+; CHECK-NEXT: .LBB0_2: # %j
+; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT: movl $1, %eax
+; CHECK-NEXT: xorl %edx, %edx
+; CHECK-NEXT: idivl %esi
+; CHECK-NEXT: movl %edx, %ecx
+; CHECK-NEXT: testb %r9b, %r9b
+; CHECK-NEXT: jne .LBB0_5
+; CHECK-NEXT: # %bb.3: # %j
+; CHECK-NEXT: # in Loop: Header=BB0_2 Depth=1
+; CHECK-NEXT: testl %r9d, %r9d
+; CHECK-NEXT: js .LBB0_5
+; CHECK-NEXT: # %bb.4:
+; CHECK-NEXT: movl %r9d, %edx
+; CHECK-NEXT: .LBB0_6: # %if.end9
+; CHECK-NEXT: testl %edx, %edx
+; CHECK-NEXT: jne .LBB0_7
+; CHECK-NEXT: .LBB0_8: # %if.end13
+; CHECK-NEXT: xorl %r8d, %r8d
+; CHECK-NEXT: jmp .LBB0_1
+; CHECK-NEXT: .LBB0_7: # %while.body.lr.ph
+; CHECK-NEXT: movl %ecx, %eax
+; CHECK-NEXT: retq
entry:
br i1 %tobool.not, label %if.end13, label %j.preheader
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