[PATCH] Recognize n/1 in the SCEV divide function
Brendon Cahoon
bcahoon at codeaurora.org
Mon Apr 20 09:06:38 PDT 2015
REPOSITORY
rL LLVM
http://reviews.llvm.org/D9003
Files:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/test/Analysis/Delinearization/divide_by_one.ll
Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -726,6 +726,13 @@
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;
Index: llvm/trunk/test/Analysis/Delinearization/divide_by_one.ll
===================================================================
--- llvm/trunk/test/Analysis/Delinearization/divide_by_one.ll
+++ llvm/trunk/test/Analysis/Delinearization/divide_by_one.ll
@@ -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
+}
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