[llvm-commits] [llvm] r78093 - in /llvm/trunk: lib/CodeGen/LowerSubregs.cpp test/CodeGen/Blackfin/2009-08-04-LowerExtract-Live.ll test/CodeGen/X86/stack-color-with-reg.ll
Jakob Stoklund Olesen
stoklund at 2pi.dk
Tue Aug 4 13:01:54 PDT 2009
Author: stoklund
Date: Tue Aug 4 15:01:11 2009
New Revision: 78093
URL: http://llvm.org/viewvc/llvm-project?rev=78093&view=rev
Log:
LowerSubregsInstructionPass::LowerExtract should not extend the live range of registers.
When LowerExtract eliminates an EXTRACT_SUBREG with a kill flag, it moves the
kill flag to the place where the sub-register is killed. This can accidentally
overlap with the use of a sibling sub-register, and we have trouble.
In the test case we have this code:
Live Ins: %R0 %R1 %R2
%R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
%R2H<def> = LOAD16fi <fi#-1>, 0, Mem:LD(2,4) [FixedStack-1 + 0]
%R1L<def> = EXTRACT_SUBREG %R1<kill>, 1
%R0L<def> = EXTRACT_SUBREG %R0<kill>, 1
%R0H<def> = ADD16 %R2H<kill>, %R2L<kill>, %AZ<imp-def>, %AN<imp-def>, %AC0<imp-def>, %V<imp-def>, %VS<imp-def>
subreg: CONVERTING: %R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
subreg: eliminated!
subreg: killed here: %R0H<def> = ADD16 %R2H, %R2L, %R2<imp-use,kill>, %AZ<imp-def>, %AN<imp-def>, %AC0<imp-def>, %V<imp-def>, %VS<imp-def>
The kill flag on %R2 is moved to the last instruction, and the live range overlaps with the definition of %R2H:
*** Bad machine code: Redefining a live physical register ***
- function: f
- basic block: 0x18358c0 (#0)
- instruction: %R2H<def> = LOAD16fi <fi#-1>, 0, Mem:LD(2,4) [FixedStack-1 + 0]
Register R2H was defined but already live.
The fix is to replace EXTRACT_SUBREG with IMPLICIT_DEF instead of eliminating
it completely:
subreg: CONVERTING: %R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
subreg: replace by: %R2L<def> = IMPLICIT_DEF %R2<kill>
Note that these IMPLICIT_DEF instructions survive to the asm output. It is
necessary to fix the stack-color-with-reg test case because of that.
Added:
llvm/trunk/test/CodeGen/Blackfin/2009-08-04-LowerExtract-Live.ll
Modified:
llvm/trunk/lib/CodeGen/LowerSubregs.cpp
llvm/trunk/test/CodeGen/X86/stack-color-with-reg.ll
Modified: llvm/trunk/lib/CodeGen/LowerSubregs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LowerSubregs.cpp?rev=78093&r1=78092&r2=78093&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LowerSubregs.cpp (original)
+++ llvm/trunk/lib/CodeGen/LowerSubregs.cpp Tue Aug 4 15:01:11 2009
@@ -103,7 +103,7 @@
MachineFunction &MF = *MBB->getParent();
const TargetRegisterInfo &TRI = *MF.getTarget().getRegisterInfo();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
-
+
assert(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
MI->getOperand(1).isReg() && MI->getOperand(1).isUse() &&
MI->getOperand(2).isImm() && "Malformed extract_subreg");
@@ -117,23 +117,20 @@
"Extract supperg source must be a physical register");
assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
"Extract destination must be in a physical register");
-
+
DOUT << "subreg: CONVERTING: " << *MI;
if (SrcReg == DstReg) {
- // No need to insert an identify copy instruction.
+ // No need to insert an identity copy instruction.
+ if (MI->getOperand(1).isKill()) {
+ // We must make sure the super-register gets killed.Replace the
+ // instruction with IMPLICIT_DEF.
+ MI->setDesc(TII.get(TargetInstrInfo::IMPLICIT_DEF));
+ MI->RemoveOperand(2); // SubIdx
+ DOUT << "subreg: replace by: " << *MI;
+ return true;
+ }
DOUT << "subreg: eliminated!";
- // Find the kill of the destination register's live range, and insert
- // a kill of the source register at that point.
- if (MI->getOperand(1).isKill() && !MI->getOperand(0).isDead())
- for (MachineBasicBlock::iterator MII =
- next(MachineBasicBlock::iterator(MI));
- MII != MBB->end(); ++MII)
- if (MII->killsRegister(DstReg, &TRI)) {
- MII->addRegisterKilled(SuperReg, &TRI, /*AddIfNotFound=*/true);
- DOUT << "\nsubreg: killed here: " << *MII;
- break;
- }
} else {
// Insert copy
const TargetRegisterClass *TRCS = TRI.getPhysicalRegisterRegClass(DstReg);
Added: llvm/trunk/test/CodeGen/Blackfin/2009-08-04-LowerExtract-Live.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Blackfin/2009-08-04-LowerExtract-Live.ll?rev=78093&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/Blackfin/2009-08-04-LowerExtract-Live.ll (added)
+++ llvm/trunk/test/CodeGen/Blackfin/2009-08-04-LowerExtract-Live.ll Tue Aug 4 15:01:11 2009
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | llc -march=bfin -join-liveintervals=0 -verify-machineinstrs
+
+; Provoke an error in LowerSubregsPass::LowerExtract where the live range of a
+; super-register is illegally extended.
+
+define i16 @f(i16 %x1, i16 %x2, i16 %x3, i16 %x4) {
+ %y1 = add i16 %x1, 1
+ %y2 = add i16 %x2, 2
+ %y3 = add i16 %x3, 3
+ %y4 = add i16 %x4, 4
+ %z12 = add i16 %y1, %y2
+ %z34 = add i16 %y3, %y4
+ %p = add i16 %z12, %z34
+ ret i16 %p
+}
Modified: llvm/trunk/test/CodeGen/X86/stack-color-with-reg.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/stack-color-with-reg.ll?rev=78093&r1=78092&r2=78093&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/stack-color-with-reg.ll (original)
+++ llvm/trunk/test/CodeGen/X86/stack-color-with-reg.ll Tue Aug 4 15:01:11 2009
@@ -1,7 +1,7 @@
; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin10 -relocation-model=pic -disable-fp-elim -color-ss-with-regs -stats -info-output-file - > %t
; RUN: grep stackcoloring %t | grep "loads eliminated"
; RUN: grep stackcoloring %t | grep "stack slot refs replaced with reg refs" | grep 5
-; RUN: grep asm-printer %t | grep 175
+; RUN: grep asm-printer %t | grep 180
type { [62 x %struct.Bitvec*] } ; type %0
type { i8* } ; type %1
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