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7cab062130
Summary: The iterative algorithm for Loop Unswitching may render some of the branches unreachable in the unswitched loops. Given the exponential nature of the algorithm, this is quite an overhead. This patch fixes this problem by selectively unswitching only those branches within a loop that are reachable from the loop header. Reviewers: Michael Zolothukin, Anna Thomas, Weiming Zhao. Subscribers: llvm-commits. Differential Revision: http://reviews.llvm.org/D26299 llvm-svn: 287925
63 lines
2.4 KiB
LLVM
63 lines
2.4 KiB
LLVM
; RUN: opt -loop-unswitch -S - < %s | FileCheck %s
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;CHECK-LABEL: @b
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;CHECK: [[Loop1:for\.end.*]]: ; preds = %for.cond.us
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;CHECK-NEXT: %[[PhiVar1:pdt.*]] = phi i32 [ %pdt.0.us, %for.cond.us ]
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;CHECK: [[Loop2:for\.end.*]]: ; preds = %for.cond.us1
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;CHECK-NEXT: %[[PhiVar2:pdt.*]] = phi i32 [ %pdt.0.us2, %for.cond.us1 ]
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;CHECK: [[Loop3:for\.end.*]]: ; preds = %for.cond
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;CHECK-NEXT: %[[PhiVar3:pdt.*]] = phi i32 [ %pdt.0, %for.cond ]
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;CHECK: [[Join1:for\.end.*]]: ; preds = %[[Loop2]], %[[Loop3]]
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;CHECK-NEXT: %[[PhiRes1:pdt.*]] = phi i32 [ %[[PhiVar3]], %[[Loop3]] ], [ %[[PhiVar2]], %[[Loop2]] ]
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;CHECK: for.end: ; preds = %[[Loop1]], %[[Join1]]
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;CHECK-NEXT: %[[PhiRes2:pdt.*]] = phi i32 [ %[[PhiRes1]], %[[Join1]] ], [ %[[PhiVar1]], %[[Loop1]] ]
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;CHECK-NEXT: ret i32 %[[PhiRes2]]
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; Function Attrs: nounwind uwtable
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define i32 @b(i32 %x, i32 %y) #0 {
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entry:
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%pdt.0 = phi i32 [ 1, %entry ], [ %pdt.2, %for.inc ]
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
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%cmp = icmp slt i32 %i.0, 100
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br i1 %cmp, label %for.body, label %for.end
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for.body: ; preds = %for.cond
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%tobool = icmp ne i32 %x, 0
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br i1 %tobool, label %if.then, label %if.else
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if.then: ; preds = %for.body
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%mul = mul nsw i32 %pdt.0, 2
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br label %if.end6
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if.else: ; preds = %for.body
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%tobool1 = icmp ne i32 %y, 0
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br i1 %tobool1, label %if.then2, label %if.else4
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if.then2: ; preds = %if.else
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%mul3 = mul nsw i32 %pdt.0, 3
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br label %if.end
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if.else4: ; preds = %if.else
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%mul5 = mul nsw i32 %pdt.0, 4
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br label %if.end
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if.end: ; preds = %if.else4, %if.then2
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%pdt.1 = phi i32 [ %mul3, %if.then2 ], [ %mul5, %if.else4 ]
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br label %if.end6
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if.end6: ; preds = %if.end, %if.then
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%pdt.2 = phi i32 [ %mul, %if.then ], [ %pdt.1, %if.end ]
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br label %for.inc
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for.inc: ; preds = %if.end6
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%inc = add nsw i32 %i.0, 1
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br label %for.cond
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for.end: ; preds = %for.cond
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ret i32 %pdt.0
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}
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