This partially fixes PR13007 (ARM CodeGen fails with large stack
alignment): for ARM and Thumb2 targets, but not for Thumb1, as it
seems stack alignment for Thumb1 targets hasn't been supported at
all.
Producing an aligned stack pointer is done by zero-ing out the lower
bits of the stack pointer. The BIC instruction was used for this.
However, the immediate field of the BIC instruction only allows to
encode an immediate that can zero out up to a maximum of the 8 lower
bits. When a larger alignment is requested, a BIC instruction cannot
be used; llvm was silently producing incorrect code in this case.
This commit fixes code generation for large stack aligments by
using the BFC instruction instead, when the BFC instruction is
available. When not, it uses 2 instructions: a right shift,
followed by a left shift to zero out the lower bits.
The lowering of ARM::Int_eh_sjlj_dispatchsetup still has code
that unconditionally uses BIC to realign the stack pointer, so it
very likely has the same problem. However, I wasn't able to
produce a test case for that. This commit adds an assert so that
the compiler will fail the assert instead of silently generating
wrong code if this is ever reached.
llvm-svn: 225446
Now that canRealignStack() understands frozen reserved registers, it is
safe to use it for aligned spill instructions.
It will only return true if the registers reserved at the beginning of
register allocation allow for dynamic stack realignment.
<rdar://problem/10625436>
llvm-svn: 147579
This patch caused a miscompilation of oggenc because a frame pointer was
suddenly needed halfway through register allocation.
<rdar://problem/10625436>
llvm-svn: 147487
ARM targets with NEON units have access to aligned vector loads and
stores that are potentially faster than unaligned operations.
Add support for spilling the callee-saved NEON registers to an aligned
stack area using 16-byte aligned NEON loads and store.
This feature is off by default, controlled by an -align-neon-spills
command line option.
llvm-svn: 147211
Use the spill slot alignment as well as the local variable alignment to
determine when the stack needs to be realigned. This works now that the
ARM target can always realign the stack by using a base pointer.
Still respect the ARMBaseRegisterInfo::canRealignStack() function
vetoing a realigned stack. Don't use aligned spill code in that case.
llvm-svn: 146997
Kristof Beyls