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Recognize n/1 in the SCEV divide function

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n/1 generates a quotient equal to n and a remainder of 0.
If this case is not recognized, then the SCEV divide() function
can return a remainder that is greater than or equal to the
denominator, which means the delinearized subscripts for the
test case will be incorrect.

Differential Revision: http://reviews.llvm.org/D9003


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235311 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Brendon Cahoon 2015-04-20 16:03:28 +00:00
parent 70273be423
commit d9b36e1007
2 changed files with 77 additions and 0 deletions
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7
lib/Analysis/ScalarEvolution.cpp
View File

@ -726,6 +726,13 @@ public:
return;
}
// A simple case when N/1. The quotient is N.
if (Denominator->isOne()) {
*Quotient = Numerator;
*Remainder = D.Zero;
return;
}
// Split the Denominator when it is a product.
if (const SCEVMulExpr *T = dyn_cast<const SCEVMulExpr>(Denominator)) {
const SCEV *Q, *R;

70
test/Analysis/Delinearization/divide_by_one.ll Normal file
View File

@ -0,0 +1,70 @@
; RUN: opt < %s -analyze -delinearize | FileCheck %s
target datalayout = "e-m:e-p:32:32-i1:32-i64:64-a:0-n32"
; Check that division by 1 can be delinearized.
;
; void test1(unsigned char *dst, int stride, int bs) {
; for (int r = bs; r >= 0; --r)
; for (int c = 0; c < bs; ++c)
; dst[r * stride + c] = dst[(r + 1) * stride + c - 1];
; }
; AddRec: {{(-1 + ((1 + %bs) * %stride)),+,(-1 * %stride)}<%for.cond1.preheader>,+,1}<nw><%for.body3>
; CHECK: Inst: %0 = load i8, i8* %arrayidx, align 1
; CHECK: Base offset: %dst
; CHECK: ArrayDecl[UnknownSize][%stride] with elements of 1 bytes.
; CHECK: ArrayRef[{(1 + %bs),+,-1}<nw><%for.cond1.preheader>][{-1,+,1}<nw><%for.body3>]
; AddRec: {{(%stride * %bs),+,(-1 * %stride)}<%for.cond1.preheader>,+,1}<nw><%for.body3>
; CHECK: Inst: store i8 %0, i8* %arrayidx7, align 1
; CHECK: Base offset: %dst
; CHECK: ArrayDecl[UnknownSize][%stride] with elements of 1 bytes.
; CHECK: ArrayRef[{%bs,+,-1}<nsw><%for.cond1.preheader>][{0,+,1}<nuw><nsw><%for.body3>]
define void @test(i8* nocapture %dst, i32 %stride, i32 %bs) {
entry:
%cmp20 = icmp sgt i32 %bs, -1
br i1 %cmp20, label %for.cond1.preheader.lr.ph, label %for.end9
for.cond1.preheader.lr.ph:
%cmp218 = icmp slt i32 0, %bs
br label %for.cond1.preheader
for.cond1.preheader:
%r.021 = phi i32 [ %bs, %for.cond1.preheader.lr.ph ], [ %dec, %for.inc8 ]
br i1 %cmp218, label %for.body3.lr.ph, label %for.inc8
for.body3.lr.ph:
%add = add nsw i32 %r.021, 1
%mul = mul nsw i32 %add, %stride
%add4 = add i32 %mul, -1
%mul5 = mul nsw i32 %r.021, %stride
br label %for.body3
for.body3:
%c.019 = phi i32 [ 0, %for.body3.lr.ph ], [ %inc, %for.body3 ]
%sub = add i32 %add4, %c.019
%arrayidx = getelementptr inbounds i8, i8* %dst, i32 %sub
%0 = load i8, i8* %arrayidx, align 1
%add6 = add nsw i32 %c.019, %mul5
%arrayidx7 = getelementptr inbounds i8, i8* %dst, i32 %add6
store i8 %0, i8* %arrayidx7, align 1
%inc = add nsw i32 %c.019, 1
%cmp2 = icmp slt i32 %inc, %bs
br i1 %cmp2, label %for.body3, label %for.cond1.for.inc8_crit_edge
for.cond1.for.inc8_crit_edge:
br label %for.inc8
for.inc8:
%dec = add nsw i32 %r.021, -1
%cmp = icmp sgt i32 %dec, -1
br i1 %cmp, label %for.cond1.preheader, label %for.cond.for.end9_crit_edge
for.cond.for.end9_crit_edge:
br label %for.end9
for.end9:
ret void
}