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[LoopUnrollRuntime] Clean up a predicate.

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Clean up a predicate I added in r229731, fix the relevant comment and
add a test case.  The earlier version is confusing to read and was also
buggy (probably not a coincidence) till Alexey fixed it in r233881.

llvm-svn: 234701
This commit is contained in:
Sanjoy Das 2015-04-12 01:24:01 +00:00
parent 70f9252a1a
commit 880c33e480
2 changed files with 47 additions and 3 deletions
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5
lib/Transforms/Utils/LoopUnrollRuntime.cpp
View File

@ -318,9 +318,8 @@ bool llvm::UnrollRuntimeLoopProlog(Loop *L, unsigned Count, LoopInfo *LI,
return false;
// This constraint lets us deal with an overflowing trip count easily; see the
// comment on ModVal below. This check is equivalent to `Log2(Count) <
// BEWidth`.
if (BEWidth < 64 && static_cast<uint64_t>(Count) > (1ULL << BEWidth))
// comment on ModVal below.
if (Log2_32(Count) > BEWidth)
return false;
// If this loop is nested, then the loop unroller changes the code in

45
test/Transforms/LoopUnroll/runtime-loop5.ll Normal file
View File

@ -0,0 +1,45 @@
; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-count=16 | FileCheck --check-prefix=UNROLL-16 %s
; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-count=4 | FileCheck --check-prefix=UNROLL-4 %s
; Given that the trip-count of this loop is a 3-bit value, we cannot
; safely unroll it with a count of anything more than 8.
define i3 @test(i3* %a, i3 %n) {
; UNROLL-16-LABEL: @test(
; UNROLL-4-LABEL: @test(
entry:
%cmp1 = icmp eq i3 %n, 0
br i1 %cmp1, label %for.end, label %for.body
; UNROLL-16-NOT: for.body.prol:
; UNROLL-4: for.body.prol:
for.body: ; preds = %for.body, %entry
; UNROLL-16-LABEL: for.body:
; UNROLL-4-LABEL: for.body:
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%sum.02 = phi i3 [ %add, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i3, i3* %a, i64 %indvars.iv
; UNROLL-16-LABEL: for.body
; UNROLL-16-LABEL: getelementptr
; UNROLL-16-LABEL-NOT: getelementptr
; UNROLL-4-LABEL: getelementptr
; UNROLL-4-LABEL: getelementptr
; UNROLL-4-LABEL: getelementptr
; UNROLL-4-LABEL: getelementptr
%0 = load i3, i3* %arrayidx
%add = add nsw i3 %0, %sum.02
%indvars.iv.next = add i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i3
%exitcond = icmp eq i3 %lftr.wideiv, %n
br i1 %exitcond, label %for.end, label %for.body
; UNROLL-16-LABEL: for.end
; UNROLL-4-LABEL: for.end
for.end: ; preds = %for.body, %entry
%sum.0.lcssa = phi i3 [ 0, %entry ], [ %add, %for.body ]
ret i3 %sum.0.lcssa
}