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c6887c7e27
In some cases, the max backedge taken count can be more conservative than the exact backedge taken count (for instance, because ScalarEvolution::getRange is not control-flow sensitive whereas computeExitLimitFromICmp can be). In these cases, computeExitLimitFromCond (specifically the bit that deals with `and` and `or` instructions) can create an ExitLimit instance with a `SCEVCouldNotCompute` max backedge count expression, but a computable exact backedge count expression. This violates an implicit SCEV assumption: a computable exact BE count should imply a computable max BE count. This change - Makes the above implicit invariant explicit by adding an assert to ExitLimit's constructor - Changes `computeExitLimitFromCond` to be more robust around conservative max backedge counts llvm-svn: 258184
21 lines
648 B
LLVM
21 lines
648 B
LLVM
; RUN: opt -S -indvars < %s | FileCheck %s
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target triple = "x86_64-unknown-linux-gnu"
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define void @main(i16 %in) {
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; CHECK-LABEL: @main(
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br label %bb2
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bb2: ; preds = %bb1.i, %bb2, %0
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%_tmp44.i = icmp slt i16 %in, 2
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br i1 %_tmp44.i, label %bb1.i, label %bb2
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bb1.i: ; preds = %bb1.i, %bb2
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%_tmp25.i = phi i16 [ %in, %bb2 ], [ %_tmp6.i, %bb1.i ]
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%_tmp6.i = add nsw i16 %_tmp25.i, 1
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%_tmp10.i = icmp sge i16 %_tmp6.i, 2
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%exitcond.i = icmp eq i16 %_tmp6.i, 2
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%or.cond = and i1 %_tmp10.i, %exitcond.i
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br i1 %or.cond, label %bb2, label %bb1.i
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}
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