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4e7b10b07f
Currently LoopUnroll generates a prologue loop before the main loop body to execute first N%UnrollFactor iterations. Also, this loop is used if trip-count can overflow - it's determined by a runtime check. However, we've been mistakenly optimizing this loop to a linear code for UnrollFactor = 2, not taking into account that it also serves as a safe version of the loop if its trip-count overflows. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222451 91177308-0d34-0410-b5e6-96231b3b80d8
31 lines
1.2 KiB
LLVM
31 lines
1.2 KiB
LLVM
; RUN: opt < %s -S -unroll-runtime -unroll-count=2 -loop-unroll | FileCheck %s
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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; When prologue is fully unrolled, the branch on its end is unconditional.
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; Unrolling it is illegal if we can't prove that trip-count+1 doesn't overflow,
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; like in this example, where it comes from an argument.
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;
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; This test is based on an example from here:
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; http://stackoverflow.com/questions/23838661/why-is-clang-optimizing-this-code-out
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;
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; CHECK: while.body.prol:
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; CHECK: br i1
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; CHECK: entry.split:
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; Function Attrs: nounwind readnone ssp uwtable
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define i32 @foo(i32 %N) #0 {
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entry:
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br label %while.body
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while.body: ; preds = %while.body, %entry
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%i = phi i32 [ 0, %entry ], [ %inc, %while.body ]
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%cmp = icmp eq i32 %i, %N
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%inc = add i32 %i, 1
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br i1 %cmp, label %while.end, label %while.body
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while.end: ; preds = %while.body
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ret i32 %i
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}
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attributes #0 = { nounwind readnone ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
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