maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/test/CodeGen/SPARC/stack-align.ll

27 lines
1.0 KiB
LLVM
Raw Normal View History

[Sparc] Account for bias in stack readjustment Summary: This was broken long ago in D12208, which failed to account for the fact that 64-bit SPARC uses a stack bias of 2047, and it is the *unbiased* value which should be aligned, not the biased one. This was seen to be an issue with Rust. Patch by: jrtc27 (James Clarke) Reviewers: jyknight, venkatra Reviewed By: jyknight Subscribers: jacob_hansen, JDevlieghere, fhahn, fedor.sergeev, llvm-commits Differential Revision: https://reviews.llvm.org/D39425 llvm-svn: 323643
2018-01-29 20:10:32 +08:00
; RUN: llc -march=sparc < %s | FileCheck %s --check-prefixes=CHECK,CHECK32
; RUN: llc -march=sparcv9 < %s | FileCheck %s --check-prefixes=CHECK,CHECK64
[Sparc] Support user-specified stack object overalignment. Note: I do not implement a base pointer, so it's still impossible to have dynamic realignment AND dynamic alloca in the same function. This also moves the code for determining the frame index reference into getFrameIndexReference, where it belongs, instead of inline in eliminateFrameIndex. [Begin long-winded screed] Now, stack realignment for Sparc is actually a silly thing to support, because the Sparc ABI has no need for it -- unlike the situation on x86, the stack is ALWAYS aligned to the required alignment for the CPU instructions: 8 bytes on sparcv8, and 16 bytes on sparcv9. However, LLVM unfortunately implements user-specified overalignment using stack realignment support, so for now, I'm going to go along with that tradition. GCC instead treats objects which have alignment specification greater than the maximum CPU-required alignment for the target as a separate block of stack memory, with their own virtual base pointer (which gets aligned). Doing it that way avoids needing to implement per-target support for stack realignment, except for the targets which *actually* have an ABI-specified stack alignment which is too small for the CPU's requirements. Further unfortunately in LLVM, the default canRealignStack for all targets effectively returns true, despite that implementing that is something a target needs to do specifically. So, the previous behavior on Sparc was to silently ignore the user's specified stack alignment. Ugh. Yet MORE unfortunate, if a target actually does return false from canRealignStack, that also causes the user-specified alignment to be *silently ignored*, rather than emitting an error. (I started looking into fixing that last, but it broke a bunch of tests, because LLVM actually *depends* on having it silently ignored: some architectures (e.g. non-linux i386) have smaller stack alignment than spilled-register alignment. But, the fact that a register needs spilling is not known until within the register allocator. And by that point, the decision to not reserve the frame pointer has been frozen in place. And without a frame pointer, stack realignment is not possible. So, canRealignStack() returns false, and needsStackRealignment() then returns false, assuming everyone can just go on their merry way assuming the alignment requirements were probably just suggestions after-all. Sigh...) Differential Revision: http://reviews.llvm.org/D12208 llvm-svn: 245668
2015-08-21 12:17:56 +08:00
declare void @stack_realign_helper(i32 %a, i32* %b)
;; This is a function where we have a local variable of 64-byte
;; alignment. We want to see that the stack is aligned (the initial
[Sparc] Don't overlap variable-sized allocas with other stack variables. On SparcV8, it was previously the case that a variable-sized alloca might overlap by 4-bytes the last fixed stack variable, effectively because 92 (the number of bytes reserved for the register spill area) != 96 (the offset added to SP for where to start a DYNAMIC_STACKALLOC). It's not as simple as changing 96 to 92, because variables that should be 8-byte aligned would then be misaligned. For now, simply increase the allocation size by 8 bytes for each dynamic allocation -- wastes space, but at least doesn't overlap. As the large comment says, doing this more efficiently will require larger changes in llvm. Also adds some test cases showing that we continue to not support dynamic stack allocation and over-alignment in the same function. llvm-svn: 285131
2016-10-26 06:13:28 +08:00
;; andn), that the local var is accessed via stack pointer (to %o1), and that
;; the argument is accessed via frame pointer not stack pointer (to %o0).
[Sparc] Support user-specified stack object overalignment. Note: I do not implement a base pointer, so it's still impossible to have dynamic realignment AND dynamic alloca in the same function. This also moves the code for determining the frame index reference into getFrameIndexReference, where it belongs, instead of inline in eliminateFrameIndex. [Begin long-winded screed] Now, stack realignment for Sparc is actually a silly thing to support, because the Sparc ABI has no need for it -- unlike the situation on x86, the stack is ALWAYS aligned to the required alignment for the CPU instructions: 8 bytes on sparcv8, and 16 bytes on sparcv9. However, LLVM unfortunately implements user-specified overalignment using stack realignment support, so for now, I'm going to go along with that tradition. GCC instead treats objects which have alignment specification greater than the maximum CPU-required alignment for the target as a separate block of stack memory, with their own virtual base pointer (which gets aligned). Doing it that way avoids needing to implement per-target support for stack realignment, except for the targets which *actually* have an ABI-specified stack alignment which is too small for the CPU's requirements. Further unfortunately in LLVM, the default canRealignStack for all targets effectively returns true, despite that implementing that is something a target needs to do specifically. So, the previous behavior on Sparc was to silently ignore the user's specified stack alignment. Ugh. Yet MORE unfortunate, if a target actually does return false from canRealignStack, that also causes the user-specified alignment to be *silently ignored*, rather than emitting an error. (I started looking into fixing that last, but it broke a bunch of tests, because LLVM actually *depends* on having it silently ignored: some architectures (e.g. non-linux i386) have smaller stack alignment than spilled-register alignment. But, the fact that a register needs spilling is not known until within the register allocator. And by that point, the decision to not reserve the frame pointer has been frozen in place. And without a frame pointer, stack realignment is not possible. So, canRealignStack() returns false, and needsStackRealignment() then returns false, assuming everyone can just go on their merry way assuming the alignment requirements were probably just suggestions after-all. Sigh...) Differential Revision: http://reviews.llvm.org/D12208 llvm-svn: 245668
2015-08-21 12:17:56 +08:00
;; CHECK-LABEL: stack_realign:
[Sparc] Account for bias in stack readjustment Summary: This was broken long ago in D12208, which failed to account for the fact that 64-bit SPARC uses a stack bias of 2047, and it is the *unbiased* value which should be aligned, not the biased one. This was seen to be an issue with Rust. Patch by: jrtc27 (James Clarke) Reviewers: jyknight, venkatra Reviewed By: jyknight Subscribers: jacob_hansen, JDevlieghere, fhahn, fedor.sergeev, llvm-commits Differential Revision: https://reviews.llvm.org/D39425 llvm-svn: 323643
2018-01-29 20:10:32 +08:00
;; CHECK32: andn %sp, 63, %sp
;; CHECK32-NEXT: ld [%fp+92], %o0
;; CHECK64: add %sp, 2047, %g1
;; CHECK64-NEXT: andn %g1, 63, %g1
;; CHECK64-NEXT: add %g1, -2047, %sp
;; CHECK64-NEXT: ld [%fp+2227], %o0
;; CHECK-NEXT: call stack_realign_helper
;; CHECK32-NEXT: add %sp, 128, %o1
;; CHECK64-NEXT: add %sp, 2239, %o1
[Sparc] Support user-specified stack object overalignment. Note: I do not implement a base pointer, so it's still impossible to have dynamic realignment AND dynamic alloca in the same function. This also moves the code for determining the frame index reference into getFrameIndexReference, where it belongs, instead of inline in eliminateFrameIndex. [Begin long-winded screed] Now, stack realignment for Sparc is actually a silly thing to support, because the Sparc ABI has no need for it -- unlike the situation on x86, the stack is ALWAYS aligned to the required alignment for the CPU instructions: 8 bytes on sparcv8, and 16 bytes on sparcv9. However, LLVM unfortunately implements user-specified overalignment using stack realignment support, so for now, I'm going to go along with that tradition. GCC instead treats objects which have alignment specification greater than the maximum CPU-required alignment for the target as a separate block of stack memory, with their own virtual base pointer (which gets aligned). Doing it that way avoids needing to implement per-target support for stack realignment, except for the targets which *actually* have an ABI-specified stack alignment which is too small for the CPU's requirements. Further unfortunately in LLVM, the default canRealignStack for all targets effectively returns true, despite that implementing that is something a target needs to do specifically. So, the previous behavior on Sparc was to silently ignore the user's specified stack alignment. Ugh. Yet MORE unfortunate, if a target actually does return false from canRealignStack, that also causes the user-specified alignment to be *silently ignored*, rather than emitting an error. (I started looking into fixing that last, but it broke a bunch of tests, because LLVM actually *depends* on having it silently ignored: some architectures (e.g. non-linux i386) have smaller stack alignment than spilled-register alignment. But, the fact that a register needs spilling is not known until within the register allocator. And by that point, the decision to not reserve the frame pointer has been frozen in place. And without a frame pointer, stack realignment is not possible. So, canRealignStack() returns false, and needsStackRealignment() then returns false, assuming everyone can just go on their merry way assuming the alignment requirements were probably just suggestions after-all. Sigh...) Differential Revision: http://reviews.llvm.org/D12208 llvm-svn: 245668
2015-08-21 12:17:56 +08:00
define void @stack_realign(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32 %g) {
entry:
%aligned = alloca i32, align 64
call void @stack_realign_helper(i32 %g, i32* %aligned)
ret void
}