[llvm-commits] [llvm] r111221 - in /llvm/trunk: lib/CodeGen/MachineBasicBlock.cpp lib/CodeGen/PHIElimination.cpp test/CodeGen/ARM/code-placement.ll test/CodeGen/X86/lsr-reuse.ll
Evan Cheng
evan.cheng at apple.com
Mon Aug 16 18:20:37 PDT 2010
Author: evancheng
Date: Mon Aug 16 20:20:36 2010
New Revision: 111221
URL: http://llvm.org/viewvc/llvm-project?rev=111221&view=rev
Log:
PHI elimination should not break back edge. It can cause some significant code placement issues. rdar://8263994
good:
LBB0_2:
mov r2, r0
. . .
mov r1, r2
bne LBB0_2
bad:
LBB0_2:
mov r2, r0
. . .
@ BB#3:
mov r1, r2
b LBB0_2
Added:
llvm/trunk/test/CodeGen/ARM/code-placement.ll
Modified:
llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
llvm/trunk/lib/CodeGen/PHIElimination.cpp
llvm/trunk/test/CodeGen/X86/lsr-reuse.ll
Modified: llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp?rev=111221&r1=111220&r2=111221&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBasicBlock.cpp Mon Aug 16 20:20:36 2010
@@ -439,6 +439,14 @@
if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
return NULL;
+ // Avoid splitting backedges of loops. It would introduce small out-of-line
+ // blocks into the loop which is very bad for code placement.
+ if (this == Succ)
+ return NULL;
+ MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>();
+ if (MLI->isLoopHeader(Succ))
+ return NULL;
+
MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
DEBUG(dbgs() << "PHIElimination splitting critical edge:"
@@ -471,8 +479,7 @@
P->getAnalysisIfAvailable<MachineDominatorTree>())
MDT->addNewBlock(NMBB, this);
- if (MachineLoopInfo *MLI =
- P->getAnalysisIfAvailable<MachineLoopInfo>())
+ if (MLI)
if (MachineLoop *TIL = MLI->getLoopFor(this)) {
// If one or the other blocks were not in a loop, the new block is not
// either, and thus LI doesn't need to be updated.
Modified: llvm/trunk/lib/CodeGen/PHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.cpp?rev=111221&r1=111220&r2=111221&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/PHIElimination.cpp Mon Aug 16 20:20:36 2010
@@ -20,6 +20,7 @@
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Function.h"
@@ -44,9 +45,9 @@
void llvm::PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveVariables>();
+ AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
- // rdar://7401784 This would be nice:
- // AU.addPreservedID(MachineLoopInfoID);
+ AU.addPreservedID(MachineLoopInfoID);
MachineFunctionPass::getAnalysisUsage(AU);
}
@@ -382,6 +383,7 @@
if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
return false; // Quick exit for basic blocks without PHIs.
+ bool Changed = false;
for (MachineBasicBlock::const_iterator BBI = MBB.begin(), BBE = MBB.end();
BBI != BBE && BBI->isPHI(); ++BBI) {
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) {
@@ -391,7 +393,7 @@
// (not considering PHI nodes). If the register is live in to this block
// anyway, we would gain nothing from splitting.
if (!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB))
- PreMBB->SplitCriticalEdge(&MBB, this);
+ Changed |= PreMBB->SplitCriticalEdge(&MBB, this) != 0;
}
}
return true;
Added: llvm/trunk/test/CodeGen/ARM/code-placement.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/code-placement.ll?rev=111221&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/code-placement.ll (added)
+++ llvm/trunk/test/CodeGen/ARM/code-placement.ll Mon Aug 16 20:20:36 2010
@@ -0,0 +1,29 @@
+; RUN: llc < %s -mtriple=armv7-apple-darwin | FileCheck %s
+; PHI elimination shouldn't break backedge.
+; rdar://8263994
+
+%struct.list_data_s = type { i16, i16 }
+%struct.list_head = type { %struct.list_head*, %struct.list_data_s* }
+
+define arm_apcscc %struct.list_head* @t(%struct.list_head* %list) nounwind {
+entry:
+ %0 = icmp eq %struct.list_head* %list, null
+ br i1 %0, label %bb2, label %bb
+
+bb:
+; CHECK: LBB0_2:
+; CHECK: bne LBB0_2
+; CHECK-NOT: b LBB0_2
+; CHECK: bx lr
+ %list_addr.05 = phi %struct.list_head* [ %2, %bb ], [ %list, %entry ]
+ %next.04 = phi %struct.list_head* [ %list_addr.05, %bb ], [ null, %entry ]
+ %1 = getelementptr inbounds %struct.list_head* %list_addr.05, i32 0, i32 0
+ %2 = load %struct.list_head** %1, align 4
+ store %struct.list_head* %next.04, %struct.list_head** %1, align 4
+ %3 = icmp eq %struct.list_head* %2, null
+ br i1 %3, label %bb2, label %bb
+
+bb2:
+ %next.0.lcssa = phi %struct.list_head* [ null, %entry ], [ %list_addr.05, %bb ]
+ ret %struct.list_head* %next.0.lcssa
+}
Modified: llvm/trunk/test/CodeGen/X86/lsr-reuse.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/lsr-reuse.ll?rev=111221&r1=111220&r2=111221&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/lsr-reuse.ll (original)
+++ llvm/trunk/test/CodeGen/X86/lsr-reuse.ll Mon Aug 16 20:20:36 2010
@@ -464,7 +464,7 @@
; And the one at %bb68, where we want to be sure to use superhero mode:
-; CHECK: BB10_10:
+; CHECK: BB10_9:
; CHECK-NEXT: movaps 48(%r{{[^,]*}}), %xmm{{.*}}
; CHECK-NEXT: mulps %xmm{{.*}}, %xmm{{.*}}
; CHECK-NEXT: movaps 32(%r{{[^,]*}}), %xmm{{.*}}
@@ -484,7 +484,7 @@
; CHECK-NEXT: addq $64, %r{{.*}}
; CHECK-NEXT: addq $64, %r{{.*}}
; CHECK-NEXT: addq $-16, %r{{.*}}
-; CHECK-NEXT: BB10_11:
+; CHECK-NEXT: BB10_10:
; CHECK-NEXT: cmpq $15, %r{{.*}}
; CHECK-NEXT: jg
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