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ExpandPostRAPseudos should transfer implicit uses, not only implicit defs

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Previously, we would expand:
%BL<def> = COPY %DL<kill>, %EBX<imp-use,kill>, %EBX<imp-def>
Into:
%BL<def> = MOV8rr %DL<kill>, %EBX<imp-def>
Dropping the imp-use on the floor.

That confused CriticalAntiDepBreaker, which (correctly) assumes that if an
instruction defs but doesn't use a register, that register is dead immediately
before the instruction - while in this case, the high lanes of EBX can be very
much alive.

This fixes PR28560.

Differential Revision: https://reviews.llvm.org/D22425

llvm-svn: 275634
This commit is contained in:
Michael Kuperstein 2016-07-15 22:31:14 +00:00
parent cd643a03d0
commit 0c6bc1e223
3 changed files with 22 additions and 12 deletions
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20
lib/CodeGen/ExpandPostRAPseudos.cpp
View File

@ -51,7 +51,7 @@ private:
bool LowerSubregToReg(MachineInstr *MI);
bool LowerCopy(MachineInstr *MI);
void TransferImplicitDefs(MachineInstr *MI);
void TransferImplicitOperands(MachineInstr *MI);
};
} // end anonymous namespace
@ -61,20 +61,16 @@ char &llvm::ExpandPostRAPseudosID = ExpandPostRA::ID;
INITIALIZE_PASS(ExpandPostRA, "postrapseudos",
"Post-RA pseudo instruction expansion pass", false, false)
/// TransferImplicitDefs - MI is a pseudo-instruction, and the lowered
/// replacement instructions immediately precede it. Copy any implicit-def
/// TransferImplicitOperands - MI is a pseudo-instruction, and the lowered
/// replacement instructions immediately precede it. Copy any implicit
/// operands from MI to the replacement instruction.
void
ExpandPostRA::TransferImplicitDefs(MachineInstr *MI) {
void ExpandPostRA::TransferImplicitOperands(MachineInstr *MI) {
MachineBasicBlock::iterator CopyMI = MI;
--CopyMI;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isImplicit() || MO.isUse())
continue;
CopyMI->addOperand(MachineOperand::CreateReg(MO.getReg(), true, true));
}
for (const MachineOperand &MO : MI->implicit_operands())
if (MO.isReg())
CopyMI->addOperand(MO);
}
bool ExpandPostRA::LowerSubregToReg(MachineInstr *MI) {
@ -167,7 +163,7 @@ bool ExpandPostRA::LowerCopy(MachineInstr *MI) {
DstMO.getReg(), SrcMO.getReg(), SrcMO.isKill());
if (MI->getNumOperands() > 2)
TransferImplicitDefs(MI);
TransferImplicitOperands(MI);
DEBUG({
MachineBasicBlock::iterator dMI = MI;
dbgs() << "replaced by: " << *(--dMI);

1
test/CodeGen/ARM/twoaddrinstr.ll
View File

@ -5,6 +5,7 @@ define void @PR13378() nounwind {
; This was orriginally a crasher trying to schedule the instructions.
; CHECK-LABEL: PR13378:
; CHECK: vld1.32
; CHECK-NEXT: vmov.i32
; CHECK-NEXT: vst1.32
; CHECK-NEXT: vst1.32
; CHECK-NEXT: vmov.f32

13
test/CodeGen/X86/pr28560.ll Normal file
View File

@ -0,0 +1,13 @@
; RUN: llc -mtriple=i686-pc-linux -print-after=postrapseudos < %s 2>&1 | FileCheck %s
; CHECK: MOV8rr %{{[A-D]}}L, %E[[R:[A-D]]]X<imp-use,kill>, %E[[R]]X<imp-def>
define i32 @foo(i32 %i, i32 %k, i8* %p) {
%f = icmp ne i32 %i, %k
%s = zext i1 %f to i8
%ret = zext i1 %f to i32
br label %next
next:
%d = add i8 %s, 5
store i8 %d, i8* %p
ret i32 %ret
}