https://llvm.org/bugs/show_bug.cgi?id=23772
Bug ID: 23772
Summary: [AArch64] r226200 can emit illegal thumb2 instruction:
"sub sp, r12, #80"
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
Classification: Unclassified
r226200 allows coalescing into SP but missed a corner case:
%vreg907<def> = COPY %SP; GPRnopc:%vreg907
%vreg908<def> = t2SUBri %vreg907, 80, pred:14, pred:%noreg, opt:%noreg;
GPRnopc:%vreg908,%vreg907
%SP<def> = COPY %vreg908; GPRnopc:%vreg908
When %vreg908 is coalesced into SP but %vreg907 is not, it's likely to emit an
illegal instruction:
sub sp, r12, #80
In Thumb2, we can only use SP as Rd if and only if Rn is also SP. This patch,
when trying remove "%SP<def> = COPY %vreg908", checks if %vreg907 is SP
already. If not, be conservative and do not coalesce %vreg908 into SP.
http://reviews.llvm.org/D10287
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