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AMDGPU: Fix use-after-free in SIOptimizeExecMasking

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Summary:
There was a bug with sequences like

   s_mov_b64 s[0:1], exec
   s_and_b64 s[2:3]<def>, s[0:1], s[2:3]<kill>
   ...
   s_mov_b64_term exec, s[2:3]

because s[2:3] was defined and used in the same instruction, ending up with
SaveExecInst inside OtherUseInsts.

Note that the test case also exposes an unrelated bug.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98028

Reviewers: tstellarAMD, arsenm

Subscribers: kzhuravl, wdng, yaxunl, llvm-commits, tony-tye

Differential Revision: https://reviews.llvm.org/D25306

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283528 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nicolai Haehnle 2016-10-07 08:40:14 +00:00
parent a47cbd993e
commit f3907ede55
2 changed files with 43 additions and 1 deletions
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5
lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
View File

@ -248,14 +248,17 @@ bool SIOptimizeExecMasking::runOnMachineFunction(MachineFunction &MF) {
if (J->readsRegister(CopyFromExec, TRI)) {
SaveExecInst = &*J;
DEBUG(dbgs() << "Found save exec op: " << *SaveExecInst << '\n');
continue;
} else {
DEBUG(dbgs() << "Instruction does not read exec copy: " << *J << '\n');
break;
}
}
if (SaveExecInst && J->readsRegister(CopyToExec, TRI))
if (SaveExecInst && J->readsRegister(CopyToExec, TRI)) {
assert(SaveExecInst != &*J);
OtherUseInsts.push_back(&*J);
}
}
if (!SaveExecInst)

39
test/CodeGen/AMDGPU/branch-condition-and.ll Normal file
View File

@ -0,0 +1,39 @@
; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
; This used to crash because during intermediate control flow lowering, there
; was a sequence
; s_mov_b64 s[0:1], exec
; s_and_b64 s[2:3], s[0:1], s[2:3] ; def & use of the same register pair
; ...
; s_mov_b64_term exec, s[2:3]
; that was not treated correctly.
;
; GCN-LABEL: {{^}}ham:
; GCN-DAG: v_cmp_lt_f32_e64 [[OTHERCC:s\[[0-9]+:[0-9]+\]]],
; GCN-DAG: v_cmp_lt_f32_e32 vcc,
; GCN: s_and_b64 [[AND:s\[[0-9]+:[0-9]+\]]], vcc, [[OTHERCC]]
; GCN: s_and_saveexec_b64 [[SAVED:s\[[0-9]+:[0-9]+\]]], [[AND]]
; GCN: s_xor_b64 [[SAVED]], exec, [[SAVED]]
;
; TODO: The following sequence is a bug (missing s_endpgm)!
;
; GCN: s_branch [[BB:BB[0-9]+_[0-9]+]]
; GCN: [[BB]]:
; GCN-NEXT: .Lfunc_end0:
define amdgpu_ps void @ham(float %arg, float %arg1) #0 {
bb:
%tmp = fcmp ogt float %arg, 0.000000e+00
%tmp2 = fcmp ogt float %arg1, 0.000000e+00
%tmp3 = and i1 %tmp, %tmp2
br i1 %tmp3, label %bb4, label %bb5
bb4: ; preds = %bb
unreachable
bb5: ; preds = %bb
ret void
}
attributes #0 = { nounwind readonly "InitialPSInputAddr"="36983" }
attributes #1 = { nounwind readnone }