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LoopVectorize: Use the widest induction variable type

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Use the widest induction type encountered for the cannonical induction variable.

We used to turn the following loop into an empty loop because we used i8 as
induction variable type and truncated 1024 to 0 as trip count.

int a[1024];
void fail() {
  int reverse_induction = 1023;
  unsigned char forward_induction = 0;
  while ((reverse_induction) >= 0) {
    forward_induction++;
    a[reverse_induction] = forward_induction;
    --reverse_induction;
  }
}

radar://13862901

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181667 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer
2013-05-11 23:04:28 +00:00
parent 6bb539a643
commit 9b5d70f076
2 changed files with 138 additions and 21 deletions
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69
test/Transforms/LoopVectorize/reverse_induction.ll
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@@ -77,3 +77,72 @@ loopend:
}
@a = common global [1024 x i32] zeroinitializer, align 16
; We incorrectly transformed this loop into an empty one because we left the
; induction variable in i8 type and truncated the exit value 1024 to 0.
; int a[1024];
;
; void fail() {
; int reverse_induction = 1023;
; unsigned char forward_induction = 0;
; while ((reverse_induction) >= 0) {
; forward_induction++;
; a[reverse_induction] = forward_induction;
; --reverse_induction;
; }
; }
; CHECK: reverse_forward_induction_i64_i8
; CHECK: vector.body
; CHECK: %index = phi i64 [ 0, %vector.ph ], [ %index.next, %vector.body ]
; CHECK: %normalized.idx = sub i64 %index, 0
; CHECK: %reverse.idx = sub i64 1023, %normalized.idx
; CHECK: trunc i64 %index to i8
define void @reverse_forward_induction_i64_i8() {
entry:
br label %while.body
while.body:
%indvars.iv = phi i64 [ 1023, %entry ], [ %indvars.iv.next, %while.body ]
%forward_induction.05 = phi i8 [ 0, %entry ], [ %inc, %while.body ]
%inc = add i8 %forward_induction.05, 1
%conv = zext i8 %inc to i32
%arrayidx = getelementptr inbounds [1024 x i32]* @a, i64 0, i64 %indvars.iv
store i32 %conv, i32* %arrayidx, align 4
%indvars.iv.next = add i64 %indvars.iv, -1
%0 = trunc i64 %indvars.iv to i32
%cmp = icmp sgt i32 %0, 0
br i1 %cmp, label %while.body, label %while.end
while.end:
ret void
}
; CHECK: reverse_forward_induction_i64_i8_signed
; CHECK: vector.body:
; CHECK: %index = phi i64 [ 129, %vector.ph ], [ %index.next, %vector.body ]
; CHECK: %normalized.idx = sub i64 %index, 129
; CHECK: %reverse.idx = sub i64 1023, %normalized.idx
; CHECK: trunc i64 %index to i8
define void @reverse_forward_induction_i64_i8_signed() {
entry:
br label %while.body
while.body:
%indvars.iv = phi i64 [ 1023, %entry ], [ %indvars.iv.next, %while.body ]
%forward_induction.05 = phi i8 [ -127, %entry ], [ %inc, %while.body ]
%inc = add i8 %forward_induction.05, 1
%conv = sext i8 %inc to i32
%arrayidx = getelementptr inbounds [1024 x i32]* @a, i64 0, i64 %indvars.iv
store i32 %conv, i32* %arrayidx, align 4
%indvars.iv.next = add i64 %indvars.iv, -1
%0 = trunc i64 %indvars.iv to i32
%cmp = icmp sgt i32 %0, 0
br i1 %cmp, label %while.body, label %while.end
while.end:
ret void
}