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[LoopUnswitch] Fix a simple bug which disables loop unswitch for select statement

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This is to fix PR34257. rL309059 takes an early return when FindLIVLoopCondition
fails to find a loop invariant condition. This is wrong and it will disable loop
unswitch for select. The patch fixes the bug.

Differential Revision: https://reviews.llvm.org/D36985


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312045 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Wei Mi 2017-08-29 21:45:11 +00:00
parent 943b3d489c
commit 0488e47901
2 changed files with 28 additions and 4 deletions
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6
lib/Transforms/Scalar/LoopUnswitch.cpp
View File

@ -705,10 +705,8 @@ bool LoopUnswitch::processCurrentLoop() {
// unswitch on it if we desire.
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
currentLoop, Changed).first;
if (!LoopCond || EqualityPropUnSafe(*LoopCond))
continue;
if (UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context), TI)) {
if (LoopCond && !EqualityPropUnSafe(*LoopCond) &&
UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context), TI)) {
++NumBranches;
return true;
}

26
test/Transforms/LoopUnswitch/unswitch-select.ll Normal file
View File

@ -0,0 +1,26 @@
; REQUIRES: asserts
; RUN: opt < %s -loop-unswitch -disable-output -stats 2>&1| FileCheck %s
; Check the select statement in the loop will be unswitched.
; CHECK: 1 loop-unswitch - Number of selects unswitched
define i32 @test(i1 zeroext %x, i32 %a) local_unnamed_addr #0 {
entry:
br label %while.cond
while.cond: ; preds = %while.body, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %while.body ]
%s.0 = phi i32 [ %a, %entry ], [ %add, %while.body ]
%cmp = icmp slt i32 %i.0, 10000
br i1 %cmp, label %while.body, label %while.end
while.body: ; preds = %while.cond
%cond = select i1 %x, i32 %a, i32 %i.0
%add = add nsw i32 %s.0, %cond
%inc = add nsw i32 %i.0, 1
br label %while.cond
while.end: ; preds = %while.cond
%s.0.lcssa = phi i32 [ %s.0, %while.cond ]
ret i32 %s.0.lcssa
}