maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[X86] Mark all byval parameters as aliased 

This is a fix for PR30290: by marking all byval stack slots as being aliased,
the instruction scheduler is more conservative about rescheduling memory
accesses to such stack slots as an LLVM Value* might alias it. This fixes
errors such as in the patched test case, where reads and writes to a data
structure are illegally mixed.

This could be fixed better in the future with better analysis for the
instruction scheduler to know what Values alias what stack slots.

Differential Revision: https://reviews.llvm.org/D45022

llvm-svn: 331749
This commit is contained in:
Jeremy Morse 2018-05-08 09:18:01 +00:00
parent c47f799289
commit 4f799c027e
2 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -2839,7 +2839,11 @@ X86TargetLowering::LowerMemArgument(SDValue Chain, CallingConv::ID CallConv,
if (Flags.isByVal()) {
unsigned Bytes = Flags.getByValSize();
if (Bytes == 0) Bytes = 1; // Don't create zero-sized stack objects.
int FI = MFI.CreateFixedObject(Bytes, VA.getLocMemOffset(), isImmutable);
// FIXME: For now, all byval parameter objects are marked as aliasing. This
// can be improved with deeper analysis.
int FI = MFI.CreateFixedObject(Bytes, VA.getLocMemOffset(), isImmutable,
/*isAliased=*/true);
// Adjust SP offset of interrupt parameter.
if (CallConv == CallingConv::X86_INTR) {
MFI.setObjectOffset(FI, Offset);

6
llvm/test/CodeGen/X86/pr30290.ll
View File

@ -5,10 +5,6 @@
; When broken, five "1" constants are written into the byval %struct.face,
; but the subsequent byval read of that struct (call to bar) gets re-ordered
; before those writes, illegally.
;
; FIXME: the output shown below is the broken output of llc, "movl $1" is
; scheduled after the copy between byval arguments starts. This will be fixed
; with the patch in review D45022.
source_filename = "test.c"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"
@ -26,8 +22,8 @@ define void @foo(%struct.face* byval nocapture align 8) local_unnamed_addr {
; CHECK-NEXT: .cfi_def_cfa_offset 48
; CHECK-NEXT: vmovaps {{.*#+}} xmm0 = [1,1,1,1]
; CHECK-NEXT: vmovaps %xmm0, {{[0-9]+}}(%rsp)
; CHECK-NEXT: vmovups {{[0-9]+}}(%rsp), %xmm0
; CHECK-NEXT: movl $1, {{[0-9]+}}(%rsp)
; CHECK-NEXT: vmovups {{[0-9]+}}(%rsp), %xmm0
; CHECK-NEXT: vmovups %xmm0, {{[0-9]+}}(%rsp)
; CHECK-NEXT: vmovaps {{[0-9]+}}(%rsp), %xmm0
; CHECK-NEXT: vmovups %xmm0, (%rsp)