http://llvm.org/bugs/show_bug.cgi?id=16393
Bug ID: 16393
Summary: lencod miscompiled on Cortex-A15 (byval issue)
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Backend: ARM
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
Classification: Unclassified
Created attachment 10717
--> http://llvm.org/bugs/attachment.cgi?id=10717&action=edit
the miscompiled function
MultiSource/Applications/JM/lencod has been failing on the arm-lnt buildbot
since r184105. After some investigation it looks like this is caused by broken
byval handling, r184105 only changed spilling decisions and uncovered the
issue.
Attached is IR for the miscompiled function (compile with llc
-mcpu=cortex-a15). It passes a very large object byval. Of particular interest
is the part:
mov r0, #1
mov r1, #2
bl RestoreMVBlock8x8
add sp, sp, #24
add sp, sp, #8192
sub sp, sp, #24
sub sp, sp, #8192
ldm r10, {r2, r3}
mov r1, sp
str r6, [sp, r8]
ldr r0, .LCPI0_0
.LBB0_57: @ %if.then248
@ =>This Inner Loop Header: Depth=1
ldr r7, [r5], #4
subs r0, r0, #4
str r7, [r1], #4
bne .LBB0_57
@ BB#58: @ %if.then248
mov r0, #1
mov r1, #3
bl RestoreMVBlock8x8
add sp, sp, #24
add sp, sp, #8192
sub lr, sp, #4096
sub r0, sp, #4096
ldr r3, [lr, #-4084] @ 4-byte Reload
movw r5, :lower16:img
ldr r12, [r0, #-4068] @ 4-byte Reload
The upper part just looks inefficient, after the second part we end up with a
corrupted stack.
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