[TailCallElim] Preserve DT and PDT
Summary:
Previously, in the NewPM pipeline, TailCallElim recalculates the DomTree when it modifies any instruction in the Function.
For example,
```
CallInst *CI = dyn_cast<CallInst>(&I);
...
CI->setTailCall();
Modified = true;
...
if (!Modified || ...)
return PreservedAnalyses::all();
```
After applying this patch, the DomTree only recalculates if needed (plus an extra insertEdge() + an extra deleteEdge() call).
When optimizing SQLite with `-passes="default<O3>"` pipeline of the newPM, the number of DomTree recalculation decreases by 6.2%, the number of nodes visited by DFS decreases by 2.9%. The time used by DomTree will decrease approximately 1%~2.5% after applying the patch.
Statistics:
```
Before the patch:
23010 dom-tree-stats - Number of DomTree recalculations
489264 dom-tree-stats - Number of nodes visited by DFS -- DomTree
After the patch:
21581 dom-tree-stats - Number of DomTree recalculations
475088 dom-tree-stats - Number of nodes visited by DFS -- DomTree
```
Reviewers: kuhar, dmgreen, brzycki, grosser, davide
Reviewed By: kuhar, brzycki
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D49982
llvm-svn: 338954
2018-08-04 16:13:47 +08:00
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; RUN: opt < %s -tailcallelim -verify-dom-info -S | FileCheck %s
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2016-11-08 05:01:49 +08:00
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define i32 @f_1(i32 %x) {
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; CHECK-LABEL: @f_1(
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wentry:
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%cond = icmp ugt i32 %x, 0
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br i1 %cond, label %return, label %body
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body:
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; CHECK: body:
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; CHECK: call i32 @f_1(i32 %y) [ "deopt"() ]
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%y = add i32 %x, 1
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%tmp = call i32 @f_1(i32 %y) [ "deopt"() ]
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ret i32 0
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return:
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ret i32 1
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}
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define i32 @f_2(i32 %x) {
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; CHECK-LABEL: @f_2
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entry:
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%cond = icmp ugt i32 %x, 0
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br i1 %cond, label %return, label %body
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body:
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; CHECK: body:
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; CHECK: call i32 @f_2(i32 %y) [ "unknown"() ]
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%y = add i32 %x, 1
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%tmp = call i32 @f_2(i32 %y) [ "unknown"() ]
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ret i32 0
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return:
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ret i32 1
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}
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declare void @func()
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define void @f_3(i1 %B) personality i8 42 {
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; CHECK-LABEL: @f_3(
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entry:
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invoke void @func()
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to label %exit unwind label %merge
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merge:
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%cs1 = catchswitch within none [label %catch] unwind to caller
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catch:
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; CHECK: catch:
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; CHECK: call void @f_3(i1 %B) [ "funclet"(token %cp) ]
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%cp = catchpad within %cs1 []
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call void @f_3(i1 %B) [ "funclet"(token %cp) ]
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ret void
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exit:
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ret void
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}
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