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[JumpThreading] Stop falsely preserving LazyValueInfo.

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JumpThreading claims to preserve LVI, but it doesn't preserve
the analyses which LVI holds a reference to (e.g. the Dominator).
In the current pass manager infrastructure, after JT runs, the
PM frees these analyses (including DominatorTree) but preserves
LVI.

CorrelatedValuePropagation runs immediately after and queries
a corrupted domtree, causing weird miscompiles.

This commit disables the preservation of LVI for the time being.
Eventually, we should either move LVI to a proper dependency
tracking mechanism (i.e. an analyses shouldn't hold references
to other analyses and compute them on demand if needed), or
we should teach all the passes preserving LVI to preserve the
analyses LVI depends on.

The new pass manager has a mechanism to invalidate LVI in case
one of the analyses it depends on becomes invalid, so this problem
shouldn't exist (at least not in this immediate form), but handling
of analyses holding references is still a very delicate subject.

Fixes PR33917 (and rustc).

llvm-svn: 309355
This commit is contained in:
Davide Italiano 2017-07-28 03:10:43 +00:00
parent aaf7680a50
commit 6e5954a153
2 changed files with 57 additions and 1 deletions
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1
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -102,7 +102,6 @@ namespace {
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<LazyValueInfoWrapperPass>();
AU.addPreserved<LazyValueInfoWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}

57
test/Transforms/JumpThreading/pr33917.ll Normal file
View File

@ -0,0 +1,57 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -jump-threading -correlated-propagation %s -S | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
declare i8* @foo()
declare i32 @rust_eh_personality() unnamed_addr
; Function Attrs: nounwind
declare void @llvm.assume(i1) #0
define void @patatino() personality i32 ()* @rust_eh_personality {
; CHECK-LABEL: @patatino(
; CHECK-NEXT: bb9:
; CHECK-NEXT: [[T9:%.*]] = invoke i8* @foo()
; CHECK-NEXT: to label [[GOOD:%.*]] unwind label [[BAD:%.*]]
; CHECK: bad:
; CHECK-NEXT: [[T10:%.*]] = landingpad { i8*, i32 }
; CHECK-NEXT: cleanup
; CHECK-NEXT: resume { i8*, i32 } [[T10]]
; CHECK: good:
; CHECK-NEXT: [[T11:%.*]] = icmp ne i8* [[T9]], null
; CHECK-NEXT: [[T12:%.*]] = zext i1 [[T11]] to i64
; CHECK-NEXT: [[COND:%.*]] = icmp eq i64 [[T12]], 1
; CHECK-NEXT: br i1 [[COND]], label [[IF_TRUE:%.*]], label [[DONE:%.*]]
; CHECK: if_true:
; CHECK-NEXT: call void @llvm.assume(i1 [[T11]])
; CHECK-NEXT: br label [[DONE]]
; CHECK: done:
; CHECK-NEXT: ret void
;
bb9:
%t9 = invoke i8* @foo()
to label %good unwind label %bad
bad:
%t10 = landingpad { i8*, i32 }
cleanup
resume { i8*, i32 } %t10
good:
%t11 = icmp ne i8* %t9, null
%t12 = zext i1 %t11 to i64
%cond = icmp eq i64 %t12, 1
br i1 %cond, label %if_true, label %done
if_true:
call void @llvm.assume(i1 %t11)
br label %done
done:
ret void
}
attributes #0 = { nounwind }