LLVM's targets need to know if stack pointer adjustments occur after the
prologue. This is needed to correctly determine if the red-zone is
appropriate to use or if a frame pointer is required.
Normally, LLVM can figure this out very precisely by reasoning about the
contents of the MachineFunction. There is an interesting corner case:
inline assembly.
The vast majority of inline assembly which will perform a push or pop is
done so to pair up with pushf or popf as appropriate. Unfortunately,
this inline assembly doesn't mark the stack pointer as clobbered
because, well, it isn't. The stack pointer is decremented and then
immediately incremented. Because of this, LLVM was changed in r256456
to conservatively assume that inline assembly contain a sequence of
stack operations. This is unfortunate because the vast majority of
inline assembly will not end up manipulating the stack pointer in any
way at all.
Instead, let's provide a more principled solution: an intrinsic.
FWIW, other compilers (MSVC and GCC among them) also provide this
functionality as an intrinsic.
llvm-svn: 256685
A frame pointer must be used if stack pointer is modified after the
prologue. LLVM will emit pushf/popf if we need to save/restore the
FLAGS register, requiring us to have a frame pointer for the function.
There is a small twist: this sequence might exist in user code via
inline-assembly. For now, conservatively assume that such functions
require a frame pointer. For real world justification, please see
clang's implementation of __readeflags.
This fixes PR25945.
llvm-svn: 256456
--
This patch enables LLVM to emit Win64-native unwind info rather than
DWARF CFI. It handles all corner cases (I hope), including stack
realignment.
Because the unwind info is not flexible enough to describe stack frames
with a gap of unknown size in the middle, such as the one caused by
stack realignment, I modified register spilling code to place all spills
into the fixed frame slots, so that they can be accessed relative to the
frame pointer.
Patch by Vadim Chugunov!
Reviewed By: rnk
Differential Revision: http://reviews.llvm.org/D4081
llvm-svn: 211691
This patch enables LLVM to emit Win64-native unwind info rather than
DWARF CFI. It handles all corner cases (I hope), including stack
realignment.
Because the unwind info is not flexible enough to describe stack frames
with a gap of unknown size in the middle, such as the one caused by
stack realignment, I modified register spilling code to place all spills
into the fixed frame slots, so that they can be accessed relative to the
frame pointer.
Patch by Vadim Chugunov!
Reviewed By: rnk
Differential Revision: http://reviews.llvm.org/D4081
llvm-svn: 211399
Adds an instruction itinerary to all x86 instructions, giving each a default latency of 1, using the InstrItinClass IIC_DEFAULT.
Sets specific latencies for Atom for the instructions in files X86InstrCMovSetCC.td, X86InstrArithmetic.td, X86InstrControl.td, and X86InstrShiftRotate.td. The Atom latencies for the remainder of the x86 instructions will be set in subsequent patches.
Adds a test to verify that the scheduler is working.
Also changes the scheduling preference to "Hybrid" for i386 Atom, while leaving x86_64 as ILP.
Patch by Preston Gurd!
llvm-svn: 149558
No one uses *-mingw64. mingw-w64 is represented as {i686|x86_64}-w64-mingw32. In llvm side, i686 and x64 can be treated as similar way.
llvm-svn: 125747
David Majnemer