297fb66484
This solves a problem with non-deterministic output from opt due to not performing dominator tree updates in a deterministic order. The problem that was analysed indicated that JumpThreading was using the DomTreeUpdater via llvm::MergeBasicBlockIntoOnlyPred. When preparing the list of updates to send to DomTreeUpdater::applyUpdates we iterated over a SmallPtrSet, which didn't give a well-defined order of updates to perform. The added domtree-updates.ll test case is an example that would result in non-deterministic printouts of the domtree. Semantically those domtree:s are equivalent, but it show the fact that when we use the domtree iterator the order in which nodes are visited depend on the order in which dominator tree updates are performed. Since some passes (at least EarlyCSE) are iterating over nodes in the dominator tree in a similar fashion as the domtree printer, then the order in which transforms are applied by such passes, transitively, also depend on the order in which dominator tree updates are performed. And taking EarlyCSE as an example the end result could be different depending on in which order the transforms are applied. Reviewed By: nikic, kuhar Differential Revision: https://reviews.llvm.org/D110292
112 lines
5.2 KiB
LLVM
112 lines
5.2 KiB
LLVM
; RUN: opt < %s -disable-output -passes='jump-threading,print<domtree>' 2>&1 | FileCheck %s
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; REQUIRES: asserts
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; The idea behind this test case is to verify that the dominator tree is
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; updated in a deterministic way. Optimizations, at least EarlyCSE, are
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; iterating the vectors that hold child nodes in the DominatorTree. Thus, the
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; end result might differ depending on the order in which nodes are inserted
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; in the dominator tree. Unfortunately this test case is quite large, but it
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; happened to trigger a non-determinism quite often when being executed
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; multipe times (it was possible to see varying results when running the test
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; less that 10 times in a row).
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; The actual problem was tracked down to llvm::MergeBasicBlockIntoOnlyPred, so
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; the important property of the test is probably that it triggers a call to
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; that function, and that the PredsOfPredBB set that is used to populate
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; Updates for the DomTreeUpdater is populated with more than one entry.
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; CHECK: Inorder Dominator Tree: DFSNumbers invalid: 0 slow queries.
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; CHECK-NEXT: [1] %entry {4294967295,4294967295} [0]
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; CHECK-NEXT: [2] %for.cond1 {4294967295,4294967295} [1]
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; CHECK-NEXT: [3] %for.inc19 {4294967295,4294967295} [2]
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; CHECK-NEXT: [3] %if.then {4294967295,4294967295} [2]
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; CHECK-NEXT: [4] %for.cond5.preheader {4294967295,4294967295} [3]
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; CHECK-NEXT: [5] %cleanup {4294967295,4294967295} [4]
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; CHECK-NEXT: [6] %cleanup16 {4294967295,4294967295} [5]
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; CHECK-NEXT: [7] %unreachable {4294967295,4294967295} [6]
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; CHECK-NEXT: [7] %for.end21 {4294967295,4294967295} [6]
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; CHECK-NEXT: [5] %for.body7 {4294967295,4294967295} [4]
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; CHECK-NEXT: [6] %for.inc {4294967295,4294967295} [5]
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; CHECK-NEXT: [5] %return {4294967295,4294967295} [4]
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; CHECK-NEXT: [3] %cleanup16.thread {4294967295,4294967295} [2]
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; CHECK-NEXT: [2] %infinite.loop {4294967295,4294967295} [1]
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; CHECK-NEXT: Roots: %entry
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@a = dso_local local_unnamed_addr global i16 0, align 1
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; Function Attrs: nounwind
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define dso_local i16 @g(i16 %a0, i16 %a1, i16 %a2, i16 %a3) local_unnamed_addr {
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entry:
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%tobool.not = icmp eq i16 %a0, 0
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br i1 %tobool.not, label %for.cond1, label %infinite.loop
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infinite.loop: ; preds = %infinite.loop, %entry
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br label %infinite.loop
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for.cond1: ; preds = %for.inc19, %entry
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%retval.0 = phi i16 [ %retval.3, %for.inc19 ], [ undef, %entry ]
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%i.0 = phi i16 [ %i.3, %for.inc19 ], [ undef, %entry ]
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%tobool2.not = icmp eq i16 %a1, 0
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br i1 %tobool2.not, label %if.end15, label %if.then
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if.then: ; preds = %for.cond1
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%tobool3.not = icmp eq i16 %a2, 0
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br i1 %tobool3.not, label %if.end15, label %for.cond5.preheader
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for.cond5.preheader: ; preds = %if.then
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%tobool8.not = icmp eq i16 %a3, 0
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%tobool6.not31 = icmp eq i16 %i.0, 0
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br i1 %tobool6.not31, label %for.end10, label %for.body7
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for.body7: ; preds = %for.inc, %for.cond5.preheader
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%i.132 = phi i16 [ %inc, %for.inc ], [ %i.0, %for.cond5.preheader ]
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br i1 %tobool8.not, label %for.inc, label %cleanup
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for.inc: ; preds = %for.body7
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%inc = add i16 %i.132, 1
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%tobool6.not = icmp eq i16 %inc, 0
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br i1 %tobool6.not, label %for.end10, label %for.body7
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for.end10: ; preds = %for.inc, %for.cond5.preheader
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%i.1.lcssa = phi i16 [ %i.0, %for.cond5.preheader ], [ 0, %for.inc ]
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%.26 = select i1 %tobool8.not, i32 0, i32 4
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br label %cleanup
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cleanup: ; preds = %for.end10, %for.body7
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%i.128 = phi i16 [ %i.1.lcssa, %for.end10 ], [ %i.0, %for.body7 ]
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%retval.1 = phi i16 [ %retval.0, %for.end10 ], [ 1, %for.body7 ]
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%cond = phi i1 [ %tobool8.not, %for.end10 ], [ false, %for.body7 ]
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%cleanup.dest.slot.0 = phi i32 [ %.26, %for.end10 ], [ 1, %for.body7 ]
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br i1 %cond, label %if.end15, label %cleanup16
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if.end15: ; preds = %cleanup, %if.then, %for.cond1
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%retval.2 = phi i16 [ %retval.1, %cleanup ], [ %retval.0, %if.then ], [ %retval.0, %for.cond1 ]
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%i.2 = phi i16 [ %i.128, %cleanup ], [ %i.0, %if.then ], [ %i.0, %for.cond1 ]
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store i16 0, i16* @a, align 1
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br label %cleanup16
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cleanup16: ; preds = %if.end15, %cleanup
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%retval.3 = phi i16 [ %retval.2, %if.end15 ], [ %retval.1, %cleanup ]
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%i.3 = phi i16 [ %i.2, %if.end15 ], [ %i.128, %cleanup ]
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%cleanup.dest.slot.1 = phi i32 [ 0, %if.end15 ], [ %cleanup.dest.slot.0, %cleanup ]
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switch i32 %cleanup.dest.slot.1, label %unreachable [
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i32 0, label %for.inc19
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i32 1, label %return
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i32 4, label %for.end21
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]
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for.inc19: ; preds = %cleanup16
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br label %for.cond1
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for.end21: ; preds = %cleanup16
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br label %return
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return: ; preds = %for.end21, %cleanup16
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%retval.4 = phi i16 [ 17, %for.end21 ], [ %retval.3, %cleanup16 ]
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ret i16 %retval.4
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unreachable: ; preds = %cleanup16
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unreachable
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}
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