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-rw-r--r--lib/CodeGen/MachineSink.cpp60
-rw-r--r--test/CodeGen/X86/MachineSink-CritEdge.ll6
-rw-r--r--test/CodeGen/X86/sink-hoist.ll39
3 files changed, 85 insertions, 20 deletions
diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp
index 72676faa89..7b4bc15d8c 100644
--- a/lib/CodeGen/MachineSink.cpp
+++ b/lib/CodeGen/MachineSink.cpp
@@ -25,6 +25,7 @@
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
@@ -61,6 +62,7 @@ namespace {
bool ProcessBlock(MachineBasicBlock &MBB);
bool SinkInstruction(MachineInstr *MI, bool &SawStore);
bool AllUsesDominatedByBlock(unsigned Reg, MachineBasicBlock *MBB) const;
+ bool LiveOutOfBasicBlock(const MachineInstr *MI, unsigned Reg) const;
};
} // end anonymous namespace
@@ -166,6 +168,44 @@ bool MachineSinking::ProcessBlock(MachineBasicBlock &MBB) {
return MadeChange;
}
+/// LiveOutOfBasicBlock - Determine if the physical register, defined and dead
+/// in MI, is live on exit from the basic block.
+bool MachineSinking::LiveOutOfBasicBlock(const MachineInstr *MI,
+ unsigned Reg) const {
+ assert(TargetRegisterInfo::isPhysicalRegister(Reg) &&
+ "Only want to determine if a physical register is live out of a BB!");
+
+ const MachineBasicBlock *MBB = MI->getParent();
+ SmallSet<unsigned, 8> KilledRegs;
+ MachineBasicBlock::const_iterator I = MBB->end();
+ MachineBasicBlock::const_iterator E = MBB->begin();
+ assert(I != E && "How can there be an empty block at this point?!");
+
+ // Loop through the instructions bottom-up. If we see a kill of the preg
+ // first, then it's not live out of the BB. If we see a use or def first, then
+ // we assume that it is live out of the BB.
+ do {
+ const MachineInstr &CurMI = *--I;
+
+ for (unsigned i = 0, e = CurMI.getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = CurMI.getOperand(i);
+ if (!MO.isReg()) continue; // Ignore non-register operands.
+
+ unsigned MOReg = MO.getReg();
+ if (MOReg == 0) continue;
+
+ if (MOReg == Reg) {
+ if (MO.isKill())
+ return false;
+ if (MO.isUse() || MO.isDef())
+ return true;
+ }
+ }
+ } while (I != E);
+
+ return false;
+}
+
/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
@@ -188,6 +228,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// SuccToSinkTo - This is the successor to sink this instruction to, once we
// decide.
MachineBasicBlock *SuccToSinkTo = 0;
+ SmallVector<unsigned, 4> PhysRegs;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
@@ -216,9 +257,12 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
if (AllocatableSet.test(AliasReg))
return false;
}
- } else if (!MO.isDead()) {
- // A def that isn't dead. We can't move it.
- return false;
+ } else {
+ if (!MO.isDead())
+ // A def that isn't dead. We can't move it.
+ return false;
+ else
+ PhysRegs.push_back(Reg);
}
} else {
// Virtual register uses are always safe to sink.
@@ -281,7 +325,15 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// happen with loops.
if (MI->getParent() == SuccToSinkTo)
return false;
-
+
+ // If the instruction to move defines a dead physical register which is live
+ // when leaving the basic block, don't move it because it could turn into a
+ // "zombie" define of that preg. E.g., EFLAGS. (<rdar://problem/8030636>)
+ for (SmallVectorImpl<unsigned>::const_iterator
+ I = PhysRegs.begin(), E = PhysRegs.end(); I != E; ++I)
+ if (LiveOutOfBasicBlock(MI, *I))
+ return false;
+
DEBUG(dbgs() << "Sink instr " << *MI << "\tinto block " << *SuccToSinkTo);
// If the block has multiple predecessors, this would introduce computation on
diff --git a/test/CodeGen/X86/MachineSink-CritEdge.ll b/test/CodeGen/X86/MachineSink-CritEdge.ll
index 74a1049772..db06b329f9 100644
--- a/test/CodeGen/X86/MachineSink-CritEdge.ll
+++ b/test/CodeGen/X86/MachineSink-CritEdge.ll
@@ -1,4 +1,10 @@
; RUN: llc < %s | FileCheck %s
+; XFAIL: *
+;
+; See <rdar://problem/8030636>. This test isn't valid after we made machine
+; sinking more conservative about sinking instructions that define a preg into a
+; block when we don't know if the preg is killed within the current block.
+
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0.0"
diff --git a/test/CodeGen/X86/sink-hoist.ll b/test/CodeGen/X86/sink-hoist.ll
index 031c01e9af..acba5288c0 100644
--- a/test/CodeGen/X86/sink-hoist.ll
+++ b/test/CodeGen/X86/sink-hoist.ll
@@ -44,26 +44,33 @@ return:
; Sink instructions with dead EFLAGS defs.
-; CHECK: zzz:
-; CHECK: je
-; CHECK-NEXT: orb
-
-define zeroext i8 @zzz(i8 zeroext %a, i8 zeroext %b) nounwind readnone {
-entry:
- %tmp = zext i8 %a to i32 ; <i32> [#uses=1]
- %tmp2 = icmp eq i8 %a, 0 ; <i1> [#uses=1]
- %tmp3 = or i8 %b, -128 ; <i8> [#uses=1]
- %tmp4 = and i8 %b, 127 ; <i8> [#uses=1]
- %b_addr.0 = select i1 %tmp2, i8 %tmp4, i8 %tmp3 ; <i8> [#uses=1]
- ret i8 %b_addr.0
-}
+; FIXME: Unfail the zzz test if we can correctly mark pregs with the kill flag.
+;
+; See <rdar://problem/8030636>. This test isn't valid after we made machine
+; sinking more conservative about sinking instructions that define a preg into a
+; block when we don't know if the preg is killed within the current block.
+
+
+; FIXMEHECK: zzz:
+; FIXMEHECK: je
+; FIXMEHECK-NEXT: orb
+
+; define zeroext i8 @zzz(i8 zeroext %a, i8 zeroext %b) nounwind readnone {
+; entry:
+; %tmp = zext i8 %a to i32 ; <i32> [#uses=1]
+; %tmp2 = icmp eq i8 %a, 0 ; <i1> [#uses=1]
+; %tmp3 = or i8 %b, -128 ; <i8> [#uses=1]
+; %tmp4 = and i8 %b, 127 ; <i8> [#uses=1]
+; %b_addr.0 = select i1 %tmp2, i8 %tmp4, i8 %tmp3 ; <i8> [#uses=1]
+; ret i8 %b_addr.0
+; }
; Codegen should hoist and CSE these constants.
; CHECK: vv:
-; CHECK: LCPI3_0(%rip), %xmm0
-; CHECK: LCPI3_1(%rip), %xmm1
-; CHECK: LCPI3_2(%rip), %xmm2
+; CHECK: LCPI2_0(%rip), %xmm0
+; CHECK: LCPI2_1(%rip), %xmm1
+; CHECK: LCPI2_2(%rip), %xmm2
; CHECK: align
; CHECK-NOT: LCPI
; CHECK: ret
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-05 13:23:40 +0000