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Don't assume it's safe to transform a loop just because it's dominated by any 

comparison. Fixes bug 1598.

llvm-svn: 40866
This commit is contained in:
Nick Lewycky 2007-08-06 18:33:46 +00:00
parent 7fffcad5c2
commit b9819f3a8b
2 changed files with 19 additions and 1 deletions
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2
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -2387,7 +2387,7 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L) {
return UnknownValue; // Not a comparison against 'n-1'.
}
else return UnknownValue;
} else if (Cond == ICmpInst::ICMP_ULT)
} else
return UnknownValue;
// cerr << "Computed Loop Trip Count as: "

18
llvm/test/Analysis/ScalarEvolution/2007-09-06-MisinterpretBranch.ll Normal file
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@ -0,0 +1,18 @@
; RUN: llvm-as < %s | opt -indvars -adce -simplifycfg | llvm-dis | grep "icmp s"
; PR1598
define i32 @f(i32 %a, i32 %b, i32 %x, i32 %y) {
entry:
%tmp3 = icmp eq i32 %a, %b ; <i1> [#uses=1]
br i1 %tmp3, label %return, label %bb
bb: ; preds = %bb, %entry
%x_addr.0 = phi i32 [ %tmp6, %bb ], [ %x, %entry ] ; <i32> [#uses=1]
%tmp6 = add i32 %x_addr.0, 1 ; <i32> [#uses=3]
%tmp9 = icmp slt i32 %tmp6, %y ; <i1> [#uses=1]
br i1 %tmp9, label %bb, label %return
return: ; preds = %bb, %entry
%x_addr.1 = phi i32 [ %x, %entry ], [ %tmp6, %bb ] ; <i32> [#uses=1]
ret i32 %x_addr.1
}