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07a3c481c6
In some case the loop exit count computation can overflow. Extend the type to
prevent most of those cases.
The problem is loops like:
int main ()
{
int a = 1;
char b = 0;
lbl:
a &= 4;
b--;
if (b) goto lbl;
return a;
}
The backedge count is 255. The induction variable type is i8. If we add one to
255 to get the exit count we overflow to zero.
To work around this issue we extend the type of the induction variable to i32 in
the case of i8 and i16.
PR17532
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195008 91177308-0d34-0410-b5e6-96231b3b80d8
111 lines
3.6 KiB
LLVM
111 lines
3.6 KiB
LLVM
; RUN: opt < %s -loop-vectorize -force-vector-unroll=1 -force-vector-width=2 -S | FileCheck %s
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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"
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; Make sure that we can handle multiple integer induction variables.
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; CHECK-LABEL: @multi_int_induction(
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; CHECK: vector.body:
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; CHECK: %index = phi i64 [ 0, %vector.ph ], [ %index.next, %vector.body ]
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; CHECK: %normalized.idx = sub i64 %index, 0
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; CHECK: %[[VAR:.*]] = trunc i64 %normalized.idx to i32
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; CHECK: %offset.idx = add i32 190, %[[VAR]]
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define void @multi_int_induction(i32* %A, i32 %N) {
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for.body.lr.ph:
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br label %for.body
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for.body:
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%indvars.iv = phi i64 [ 0, %for.body.lr.ph ], [ %indvars.iv.next, %for.body ]
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%count.09 = phi i32 [ 190, %for.body.lr.ph ], [ %inc, %for.body ]
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%arrayidx2 = getelementptr inbounds i32* %A, i64 %indvars.iv
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store i32 %count.09, i32* %arrayidx2, align 4
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%inc = add nsw i32 %count.09, 1
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%indvars.iv.next = add i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv.next to i32
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%exitcond = icmp ne i32 %lftr.wideiv, %N
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br i1 %exitcond, label %for.body, label %for.end
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for.end:
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ret void
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}
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; RUN: opt < %s -loop-vectorize -force-vector-unroll=1 -force-vector-width=2 -instcombine -S | FileCheck %s --check-prefix=IND
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; Make sure we remove unneeded vectorization of induction variables.
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; In order for instcombine to cleanup the vectorized induction variables that we
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; create in the loop vectorizer we need to perform some form of redundancy
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; elimination to get rid of multiple uses.
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; IND-LABEL: scalar_use
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; IND: br label %vector.body
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; IND: vector.body:
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; Vectorized induction variable.
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; IND-NOT: insertelement <2 x i64>
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; IND-NOT: shufflevector <2 x i64>
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; IND: br {{.*}}, label %vector.body
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define void @scalar_use(float* %a, float %b, i64 %offset, i64 %offset2, i64 %n) {
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entry:
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br label %for.body
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for.body:
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%iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
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%ind.sum = add i64 %iv, %offset
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%arr.idx = getelementptr inbounds float* %a, i64 %ind.sum
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%l1 = load float* %arr.idx, align 4
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%ind.sum2 = add i64 %iv, %offset2
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%arr.idx2 = getelementptr inbounds float* %a, i64 %ind.sum2
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%l2 = load float* %arr.idx2, align 4
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%m = fmul fast float %b, %l2
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%ad = fadd fast float %l1, %m
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store float %ad, float* %arr.idx, align 4
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%iv.next = add nuw nsw i64 %iv, 1
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%exitcond = icmp eq i64 %iv.next, %n
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br i1 %exitcond, label %loopexit, label %for.body
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loopexit:
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ret void
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}
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; Make sure that the loop exit count computation does not overflow for i8 and
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; i16. The exit count of these loops is i8/i16 max + 1. If we don't cast the
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; induction variable to a bigger type the exit count computation will overflow
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; to 0.
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; PR17532
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; CHECK-LABEL: i8_loop
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; CHECK; icmp eq i32 {{.*}}, 256
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define i32 @i8_loop() nounwind readnone ssp uwtable {
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br label %1
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; <label>:1 ; preds = %1, %0
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%a.0 = phi i32 [ 1, %0 ], [ %2, %1 ]
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%b.0 = phi i8 [ 0, %0 ], [ %3, %1 ]
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%2 = and i32 %a.0, 4
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%3 = add i8 %b.0, -1
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%4 = icmp eq i8 %3, 0
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br i1 %4, label %5, label %1
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; <label>:5 ; preds = %1
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ret i32 %2
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}
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; CHECK-LABEL: i16_loop
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; CHECK; icmp eq i32 {{.*}}, 65536
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define i32 @i16_loop() nounwind readnone ssp uwtable {
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br label %1
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; <label>:1 ; preds = %1, %0
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%a.0 = phi i32 [ 1, %0 ], [ %2, %1 ]
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%b.0 = phi i16 [ 0, %0 ], [ %3, %1 ]
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%2 = and i32 %a.0, 4
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%3 = add i16 %b.0, -1
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%4 = icmp eq i16 %3, 0
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br i1 %4, label %5, label %1
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; <label>:5 ; preds = %1
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ret i32 %2
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}
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