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MachineCopyPropagation: Respect implicit operands of COPY

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The code missed to check implicit operands of COPY instructions for
defs/uses.

Differential Revision: https://reviews.llvm.org/D29522

llvm-svn: 294088
This commit is contained in:
Matthias Braun 2017-02-04 02:27:20 +00:00
parent 6977c6a133
commit 95a43d873a
2 changed files with 53 additions and 17 deletions
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48
lib/CodeGen/MachineCopyPropagation.cpp
View File

@ -61,6 +61,7 @@ namespace {
private:
void ClobberRegister(unsigned Reg);
void ReadRegister(unsigned Reg);
void CopyPropagateBlock(MachineBasicBlock &MBB);
bool eraseIfRedundant(MachineInstr &Copy, unsigned Src, unsigned Def);
@ -120,6 +121,18 @@ void MachineCopyPropagation::ClobberRegister(unsigned Reg) {
}
}
void MachineCopyPropagation::ReadRegister(unsigned Reg) {
// If 'Reg' is defined by a copy, the copy is no longer a candidate
// for elimination.
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
Reg2MIMap::iterator CI = CopyMap.find(*AI);
if (CI != CopyMap.end()) {
DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());
MaybeDeadCopies.remove(CI->second);
}
}
}
/// Return true if \p PreviousCopy did copy register \p Src to register \p Def.
/// This fact may have been obscured by sub register usage or may not be true at
/// all even though Src and Def are subregisters of the registers used in
@ -212,12 +225,14 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
// If Src is defined by a previous copy, the previous copy cannot be
// eliminated.
for (MCRegAliasIterator AI(Src, TRI, true); AI.isValid(); ++AI) {
Reg2MIMap::iterator CI = CopyMap.find(*AI);
if (CI != CopyMap.end()) {
DEBUG(dbgs() << "MCP: Copy is no longer dead: "; CI->second->dump());
MaybeDeadCopies.remove(CI->second);
}
ReadRegister(Src);
for (const MachineOperand &MO : MI->implicit_operands()) {
if (!MO.isReg() || !MO.readsReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
ReadRegister(Reg);
}
DEBUG(dbgs() << "MCP: Copy is a deletion candidate: "; MI->dump());
@ -234,6 +249,14 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
// ...
// %xmm2<def> = copy %xmm9
ClobberRegister(Def);
for (const MachineOperand &MO : MI->implicit_operands()) {
if (!MO.isReg() || !MO.isDef())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
ClobberRegister(Reg);
}
// Remember Def is defined by the copy.
for (MCSubRegIterator SR(Def, TRI, /*IncludeSelf=*/true); SR.isValid();
@ -269,17 +292,8 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
if (MO.isDef()) {
Defs.push_back(Reg);
continue;
}
// If 'Reg' is defined by a copy, the copy is no longer a candidate
// for elimination.
for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
Reg2MIMap::iterator CI = CopyMap.find(*AI);
if (CI != CopyMap.end()) {
DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());
MaybeDeadCopies.remove(CI->second);
}
}
} else if (MO.readsReg())
ReadRegister(Reg);
}
// The instruction has a register mask operand which means that it clobbers

22
test/CodeGen/ARM/machine-copyprop.mir Normal file
View File

@ -0,0 +1,22 @@
# RUN: llc -o - %s -mtriple=armv7s-- -run-pass=machine-cp | FileCheck %s
---
# Test that machine copy prop recognizes the implicit-def operands on a COPY
# as clobbering the register.
# CHECK-LABEL: name: func
# CHECK: %d2 = VMOVv2i32 2, 14, _
# CHECK: %s5 = COPY %s0, implicit %q1, implicit-def %q1
# CHECK: VST1q32 %r0, 0, %q1, 14, _
# The following two COPYs must not be removed
# CHECK: %s4 = COPY %s20, implicit-def %q1
# CHECK: %s5 = COPY %s0, implicit killed %d0, implicit %q1, implicit-def %q1
# CHECK: VST1q32 %r2, 0, %q1, 14, _
name: func
body: |
bb.0:
%d2 = VMOVv2i32 2, 14, _
%s5 = COPY %s0, implicit %q1, implicit-def %q1
VST1q32 %r0, 0, %q1, 14, _
%s4 = COPY %s20, implicit-def %q1
%s5 = COPY %s0, implicit killed %d0, implicit %q1, implicit-def %q1
VST1q32 %r2, 0, %q1, 14, _
...