[PATCH] D66330: Fix use-after-free in CodeGenPrepare
Sanjay Patel via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 16 16:13:42 PDT 2019
This revision was automatically updated to reflect the committed changes.
Closed by commit rL369168: [CodeGenPrepare] Fix use-after-free (authored by spatel, committed by ).
Changed prior to commit:
https://reviews.llvm.org/D66330?vs=215530&id=215706#toc
Repository:
rL LLVM
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D66330/new/
https://reviews.llvm.org/D66330
Files:
llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
llvm/trunk/test/Transforms/CodeGenPrepare/sink-shift-and-trunc.ll
Index: llvm/trunk/test/Transforms/CodeGenPrepare/sink-shift-and-trunc.ll
===================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/sink-shift-and-trunc.ll
+++ llvm/trunk/test/Transforms/CodeGenPrepare/sink-shift-and-trunc.ll
@@ -58,6 +58,23 @@
ret i32 %retval.0, !dbg !63
}
+; CodeGenPrepare was erasing the unused lshr instruction, but then further
+; processing the instruction after it was freed. If this bug is still present,
+; this test will always crash in an LLVM built with ASAN enabled, and may
+; crash even if ASAN is not enabled.
+
+define i32 @shift_unused(i32 %a) {
+; CHECK-LABEL: @shift_unused(
+; CHECK-NEXT: BB2:
+; CHECK-NEXT: ret i32 [[A:%.*]]
+;
+ %as = lshr i32 %a, 3
+ br label %BB2
+
+BB2:
+ ret i32 %a
+}
+
; CHECK: [[shift1_loc]] = !DILocation(line: 1
; CHECK: [[trunc1_loc]] = !DILocation(line: 2
; CHECK: [[shift2_loc]] = !DILocation(line: 3
Index: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
@@ -1682,10 +1682,11 @@
TheUse = InsertedShift;
}
- // If we removed all uses, nuke the shift.
+ // If we removed all uses, or there are none, nuke the shift.
if (ShiftI->use_empty()) {
salvageDebugInfo(*ShiftI);
ShiftI->eraseFromParent();
+ MadeChange = true;
}
return MadeChange;
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