https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64154
Bug ID: 64154
Summary: enable fuse-caller-save for Thumb1
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
For PR 63718, we disabled -fuse-caller-save for Thumb1 in arm.c:
...
/* In Thumb1 mode, we emit the epilogue in RTL, but the last insn
- epilogue_insns - does not accurately model the corresponding insns
emitted in the asm file. In particular, see the comment in thumb_exit
'Find out how many of the (return) argument registers we can corrupt'.
As a consequence, the epilogue may clobber registers without
fuse-caller-save finding out about it. Therefore, disable
fuse-caller-save
in Thumb1 mode.
TODO: Accurately model clobbers for epilogue_insns and reenable
fuse-caller-save. */
if (TARGET_THUMB1)
flag_use_caller_save = 0;
...
We want to fix the target to properly model the clobbers in the rtl insn
epilogue_insns, such that we can re-enable -fuse-caller-save.
