[llvm] r284036 - Do not remove implicit defs in BranchFolder
Krzysztof Parzyszek via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 12 12:50:58 PDT 2016
Author: kparzysz
Date: Wed Oct 12 14:50:57 2016
New Revision: 284036
URL: http://llvm.org/viewvc/llvm-project?rev=284036&view=rev
Log:
Do not remove implicit defs in BranchFolder
Branch folder removes implicit defs if they are the only non-branching
instructions in a block, and the branches do not use the defined registers.
The problem is that in some cases these implicit defs are required for
the liveness information to be correct.
Differential Revision: https://reviews.llvm.org/D25478
Added:
llvm/trunk/test/CodeGen/Hexagon/branchfolder-keep-impdef.ll
Modified:
llvm/trunk/lib/CodeGen/BranchFolding.cpp
llvm/trunk/lib/CodeGen/BranchFolding.h
llvm/trunk/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll
Modified: llvm/trunk/lib/CodeGen/BranchFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.cpp?rev=284036&r1=284035&r2=284036&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.cpp Wed Oct 12 14:50:57 2016
@@ -145,59 +145,6 @@ void BranchFolder::RemoveDeadBlock(Machi
MLI->removeBlock(MBB);
}
-/// OptimizeImpDefsBlock - If a basic block is just a bunch of implicit_def
-/// followed by terminators, and if the implicitly defined registers are not
-/// used by the terminators, remove those implicit_def's. e.g.
-/// BB1:
-/// r0 = implicit_def
-/// r1 = implicit_def
-/// br
-/// This block can be optimized away later if the implicit instructions are
-/// removed.
-bool BranchFolder::OptimizeImpDefsBlock(MachineBasicBlock *MBB) {
- SmallSet<unsigned, 4> ImpDefRegs;
- MachineBasicBlock::iterator I = MBB->begin();
- while (I != MBB->end()) {
- if (!I->isImplicitDef())
- break;
- unsigned Reg = I->getOperand(0).getReg();
- if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
- for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
- SubRegs.isValid(); ++SubRegs)
- ImpDefRegs.insert(*SubRegs);
- } else {
- ImpDefRegs.insert(Reg);
- }
- ++I;
- }
- if (ImpDefRegs.empty())
- return false;
-
- MachineBasicBlock::iterator FirstTerm = I;
- while (I != MBB->end()) {
- if (!TII->isUnpredicatedTerminator(*I))
- return false;
- // See if it uses any of the implicitly defined registers.
- for (const MachineOperand &MO : I->operands()) {
- if (!MO.isReg() || !MO.isUse())
- continue;
- unsigned Reg = MO.getReg();
- if (ImpDefRegs.count(Reg))
- return false;
- }
- ++I;
- }
-
- I = MBB->begin();
- while (I != FirstTerm) {
- MachineInstr *ImpDefMI = &*I;
- ++I;
- MBB->erase(ImpDefMI);
- }
-
- return true;
-}
-
/// OptimizeFunction - Perhaps branch folding, tail merging and other
/// CFG optimizations on the given function. Block placement changes the layout
/// and may create new tail merging opportunities.
@@ -228,7 +175,6 @@ bool BranchFolder::OptimizeFunction(Mach
SmallVector<MachineOperand, 4> Cond;
if (!TII->analyzeBranch(MBB, TBB, FBB, Cond, true))
MadeChange |= MBB.CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
- MadeChange |= OptimizeImpDefsBlock(&MBB);
}
// Recalculate funclet membership.
Modified: llvm/trunk/lib/CodeGen/BranchFolding.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/BranchFolding.h?rev=284036&r1=284035&r2=284036&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/BranchFolding.h (original)
+++ llvm/trunk/lib/CodeGen/BranchFolding.h Wed Oct 12 14:50:57 2016
@@ -156,7 +156,6 @@ namespace llvm {
bool OptimizeBranches(MachineFunction &MF);
bool OptimizeBlock(MachineBasicBlock *MBB);
void RemoveDeadBlock(MachineBasicBlock *MBB);
- bool OptimizeImpDefsBlock(MachineBasicBlock *MBB);
bool HoistCommonCode(MachineFunction &MF);
bool HoistCommonCodeInSuccs(MachineBasicBlock *MBB);
Added: llvm/trunk/test/CodeGen/Hexagon/branchfolder-keep-impdef.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Hexagon/branchfolder-keep-impdef.ll?rev=284036&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/Hexagon/branchfolder-keep-impdef.ll (added)
+++ llvm/trunk/test/CodeGen/Hexagon/branchfolder-keep-impdef.ll Wed Oct 12 14:50:57 2016
@@ -0,0 +1,29 @@
+; RUN: llc -march=hexagon -verify-machineinstrs < %s | FileCheck %s
+;
+; Check that the testcase compiles successfully. Expect that if-conversion
+; took place.
+; CHECK-LABEL: fred:
+; CHECK: if (!p0) r1 = memw(r0 + #0)
+
+target triple = "hexagon"
+
+define void @fred(i32 %p0) local_unnamed_addr align 2 {
+b0:
+ br i1 undef, label %b1, label %b2
+
+b1: ; preds = %b0
+ %t0 = load i8*, i8** undef, align 4
+ br label %b2
+
+b2: ; preds = %b1, %b0
+ %t1 = phi i8* [ %t0, %b1 ], [ undef, %b0 ]
+ %t2 = getelementptr inbounds i8, i8* %t1, i32 %p0
+ tail call void @llvm.memmove.p0i8.p0i8.i32(i8* undef, i8* %t2, i32 undef, i32 1, i1 false) #1
+ unreachable
+}
+
+declare void @llvm.memmove.p0i8.p0i8.i32(i8* nocapture, i8* nocapture readonly, i32, i32, i1) #0
+
+attributes #0 = { argmemonly nounwind }
+attributes #1 = { nounwind }
+
Modified: llvm/trunk/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll?rev=284036&r1=284035&r2=284036&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll (original)
+++ llvm/trunk/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll Wed Oct 12 14:50:57 2016
@@ -100,6 +100,7 @@ while.end:
; CHECK-NEXT: in Loop: Header
; CHECK-NEXT: incq
; CHECK-NEXT: %for.body3.us.i
+; CHECK-NEXT: Parent Loop
; CHECK-NEXT: Inner Loop
; CHECK: testb
; CHECK: je
More information about the llvm-commits
mailing list