http://llvm.org/bugs/show_bug.cgi?id=19136
Bug ID: 19136
Summary: [ARM] crash while folding SP-update into vpush/vpop
Product: new-bugs
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 12230
--> http://llvm.org/bugs/attachment.cgi?id=12230&action=edit
llc < test.ll
When build LLVM with assertion on, it crashes:
*** Bad machine code: Using an undefined physical register ***
- function: test
- basic block: BB#2 exit (0x16e2ee0)
- instruction: %SP<def,tied1> = t2LDMIA_RET %SP<tied0>, pred:14, pred:%noreg,
%R4<def>, %PC<def>, %S0<imp-use,kill>
- operand 6: %S0<imp-use,kill>
LLVM ERROR: Found 1 machine code errors.
Without assertion, it output incorrect error.
Analysis:
Before Frame lowering:
vpush d8
sub sp, 64
....
...
s16= ....
s0 = ...
add sp, #64
vpop d8
(ret s0 implicitly)
When -Os is used, tryFoldSPUdateIntoPushPop() kicks in and tries to eliminate
"sub sp, 64" and "add sp, 64" by doing
vpush {d0-d8}, vpop {d0-d8}, which destroys s0.
The reason it uses MBB->computeRegisterLiveness() check the liveness D0.
However D0 is clobbered by S0 and assumed to be LQR_Dead.
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