2013-03-13 00:27:52 +08:00
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; REQUIRES: asserts
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2011-01-29 12:53:35 +08:00
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; Duplicate the return into if.end to enable TCE.
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[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 -tailcallelim -verify-dom-info -stats -disable-output < %s 2>&1 | FileCheck %s
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2013-01-01 22:04:36 +08:00
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; CHECK: Number of return duplicated
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2011-01-29 12:53:35 +08:00
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define i32 @fib(i32 %n) nounwind ssp {
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entry:
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%cmp = icmp slt i32 %n, 2
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br i1 %cmp, label %if.then, label %if.end
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if.then: ; preds = %entry
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br label %return
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if.end: ; preds = %entry
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%sub = add nsw i32 %n, -2
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%call = call i32 @fib(i32 %sub)
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%sub3 = add nsw i32 %n, -1
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%call4 = call i32 @fib(i32 %sub3)
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%add = add nsw i32 %call, %call4
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br label %return
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return: ; preds = %if.end, %if.then
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%retval.0 = phi i32 [ 1, %if.then ], [ %add, %if.end ]
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ret i32 %retval.0
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}
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