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LiveIntervalAnalysis: fix a crash in repairOldRegInRange 

Summary:
See the new test case for one that was (non-deterministically) crashing
on trunk and deterministically hit the assertion that I added in D23302.
Basically, the machine function contains a sequence

     DS_WRITE_B32 %vreg4, %vreg14:sub0, ...
     DS_WRITE_B32 %vreg4, %vreg14:sub0, ...
     %vreg14:sub1<def> = COPY %vreg14:sub0

and SILoadStoreOptimizer::mergeWrite2Pair merges the two DS_WRITE_B32
instructions into one before calling repairIntervalsInRange.

Now repairIntervalsInRange wants to repair %vreg14, in particular, and
ends up trying to repair %vreg14:sub1 as well, but that only becomes
active _after_ the range that is to be repaired, hence the crash due
to LR.find(...) == LR.begin() at the start of repairOldRegInRange.

I believe that just skipping those subrange is fine, but again, not too
familiar with that code.

Reviewers: MatzeB, kparzysz, tstellarAMD

Subscribers: llvm-commits, MatzeB

Differential Revision: https://reviews.llvm.org/D23303

llvm-svn: 278268
This commit is contained in:
Nicolai Haehnle 2016-08-10 18:51:14 +00:00
parent b10f6876cd
commit 02d784172c
2 changed files with 41 additions and 0 deletions
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5
llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -1396,6 +1396,11 @@ void LiveIntervals::repairOldRegInRange(const MachineBasicBlock::iterator Begin,
LaneBitmask LaneMask) {
LiveInterval::iterator LII = LR.find(endIdx);
SlotIndex lastUseIdx;
if (LII == LR.begin()) {
// This happens when the function is called for a subregister that only
// occurs _after_ the range that is to be repaired.
return;
}
if (LII != LR.end() && LII->start < endIdx)
lastUseIdx = LII->end;
else

36
llvm/test/CodeGen/AMDGPU/merge-store-crash.ll Normal file
View File

@ -0,0 +1,36 @@
; RUN: llc -march=amdgcn -mcpu=verde -verify-machineinstrs < %s | FileCheck %s
; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck %s
; This is used to crash in LiveIntervalAnalysis via SILoadStoreOptimizer
; while fixing up the merge of two ds_write instructions.
@tess_lds = external addrspace(3) global [8192 x i32]
; CHECK-LABEL: {{^}}main:
; CHECK: ds_write2_b32
; CHECK: v_mov_b32_e32 v1, v0
; CHECK: tbuffer_store_format_xyzw v[0:3],
define amdgpu_vs void @main(i32 inreg %arg) {
main_body:
%tmp = load float, float addrspace(3)* undef, align 4
%tmp1 = load float, float addrspace(3)* undef, align 4
store float %tmp, float addrspace(3)* null, align 4
%tmp2 = bitcast float %tmp to i32
%tmp3 = add nuw nsw i32 0, 1
%tmp4 = zext i32 %tmp3 to i64
%tmp5 = getelementptr [8192 x i32], [8192 x i32] addrspace(3)* @tess_lds, i64 0, i64 %tmp4
%tmp6 = bitcast i32 addrspace(3)* %tmp5 to float addrspace(3)*
store float %tmp1, float addrspace(3)* %tmp6, align 4
%tmp7 = bitcast float %tmp1 to i32
%tmp8 = insertelement <4 x i32> undef, i32 %tmp2, i32 0
%tmp9 = insertelement <4 x i32> %tmp8, i32 %tmp7, i32 1
%tmp10 = insertelement <4 x i32> %tmp9, i32 undef, i32 2
%tmp11 = insertelement <4 x i32> %tmp10, i32 undef, i32 3
call void @llvm.SI.tbuffer.store.v4i32(<16 x i8> undef, <4 x i32> %tmp11, i32 4, i32 undef, i32 %arg, i32 0, i32 14, i32 4, i32 1, i32 0, i32 1, i32 1, i32 0)
ret void
}
; Function Attrs: nounwind
declare void @llvm.SI.tbuffer.store.v4i32(<16 x i8>, <4 x i32>, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) #0
attributes #0 = { nounwind }