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ARM: When re-creating a branch via InsertBranch, preserve CPSR flags.

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In particular, this preserves the kill flag, which allows the Thumb2 cbn?z
optimization to be applied in cases where a branch has been re-created after
the live variables analysis pass, e.g. by the machine block placement pass.

This appears to be low risk; a number of other targets seem to already be
doing something similar, e.g. AArch64, PowerPC.

Differential Revision: http://reviews.llvm.org/D9184

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235639 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2015-04-23 20:31:32 +00:00
parent d9a479e5a0
commit 1ad0f74155
3 changed files with 6 additions and 5 deletions
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6
lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -410,6 +410,8 @@ ARMBaseInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
assert((Cond.size() == 2 || Cond.size() == 0) &&
"ARM branch conditions have two components!");
// For conditional branches, we use addOperand to preserve CPSR flags.
if (!FBB) {
if (Cond.empty()) { // Unconditional branch?
if (isThumb)
@ -418,13 +420,13 @@ ARMBaseInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
BuildMI(&MBB, DL, get(BOpc)).addMBB(TBB);
} else
BuildMI(&MBB, DL, get(BccOpc)).addMBB(TBB)
.addImm(Cond[0].getImm()).addReg(Cond[1].getReg());
.addImm(Cond[0].getImm()).addOperand(Cond[1]);
return 1;
}
// Two-way conditional branch.
BuildMI(&MBB, DL, get(BccOpc)).addMBB(TBB)
.addImm(Cond[0].getImm()).addReg(Cond[1].getReg());
.addImm(Cond[0].getImm()).addOperand(Cond[1]);
if (isThumb)
BuildMI(&MBB, DL, get(BOpc)).addMBB(FBB).addImm(ARMCC::AL).addReg(0);
else

2
test/CodeGen/ARM/sjlj-prepare-critical-edge.ll
View File

@ -79,7 +79,7 @@ declare void @terminatev()
; CHECK: str r0, [sp, [[OFFSET:#[0-9]+]]]
; CHECK: ldr [[R0:r[0-9]+]], [sp, [[OFFSET]]]
; CHECK: {{.*}}@ %do.body.i.i.i
; CHECK: cmp [[R0]], #0
; CHECK: cbz [[R0]]
%"class.std::__1::basic_string" = type { %"class.std::__1::__compressed_pair" }
%"class.std::__1::__compressed_pair" = type { %"class.std::__1::__libcpp_compressed_pair_imp" }

3
test/CodeGen/Thumb2/v8_IT_5.ll
View File

@ -3,8 +3,7 @@
; CHECK: it ne
; CHECK-NEXT: cmpne
; CHECK-NEXT: bne [[JUMPTARGET:.LBB[0-9]+_[0-9]+]]
; CHECK: cmp
; CHECK-NEXT: beq
; CHECK: cbz
; CHECK-NEXT: %if.else163
; CHECK-NEXT: mov.w
; CHECK-NEXT: b