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SCEV: Handle a corner case reducing AddRecExpr * AddRecExpr 

If integer overflow causes one of the terms to reach zero, that can
force the entire expression to zero.

Fixes PR12929: cast<Ty>() argument of incompatible type

llvm-svn: 157673
This commit is contained in:
Andrew Trick 2012-05-30 03:35:20 +00:00
parent 946f76bf33
commit a3f9043196
2 changed files with 49 additions and 1 deletions
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5
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -2088,9 +2088,12 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
SCEV::FlagAnyWrap);
if (Ops.size() == 2) return NewAddRec;
Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);
Ops[Idx] = NewAddRec;
Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
OpsModified = true;
AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
if (!AddRec)
break;
}
}
if (OpsModified)

45
llvm/test/Analysis/ScalarEvolution/2012-05-29-MulAddRec.ll Normal file
View File

@ -0,0 +1,45 @@
; RUN: opt < %s -S -indvars -loop-unroll | FileCheck %s
;
; loop-unroll fully unrolls the inner loop, creating an interesting
; chain of multiplication. indvars forces SCEV to run again on the
; outer loop. While reducing the recurrence at %mul3, unsigned integer overflow
; causes one of the terms to reach zero. This forces all multiples in
; the recurrence to be zero, reducing the whole thing to a constant expression.
;
; PR12929: cast<Ty>() argument of incompatible type
; CHECK: @func
; CHECK: for.cond:
; CHECK: %inc1 = phi i8 [ 0, %entry ], [ %0, %for.body ]
; CHECK: br label %for.body
; CHECK: for.body:
; CHECK: %inc.9 = add i8 %inc.8, 1
; CHECK: %0 = add i8 %inc1, 10
; CHEKC: br label %for.cond
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
define void @func() noreturn nounwind uwtable ssp {
entry:
br label %for.cond
for.cond.loopexit: ; preds = %for.body
%mul.lcssa = phi i8 [ %mul, %for.body ]
%0 = add i8 %inc1, 10
%indvars.iv.next = add i8 %indvars.iv, 10
br label %for.cond
for.cond: ; preds = %for.cond.loopexit, %entry
%indvars.iv = phi i8 [ %indvars.iv.next, %for.cond.loopexit ], [ 10, %entry ]
%mul3 = phi i8 [ undef, %entry ], [ %mul.lcssa, %for.cond.loopexit ]
%inc1 = phi i8 [ 0, %entry ], [ %0, %for.cond.loopexit ]
br label %for.body
for.body: ; preds = %for.body, %for.cond
%inc26 = phi i8 [ %inc1, %for.cond ], [ %inc, %for.body ]
%mul45 = phi i8 [ %mul3, %for.cond ], [ %mul, %for.body ]
%inc = add i8 %inc26, 1
%mul = mul i8 %inc26, %mul45
%exitcond = icmp ne i8 %inc, %indvars.iv
br i1 %exitcond, label %for.body, label %for.cond.loopexit
}