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<p class="MsoNormal">Hi ,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The following loop fails to be vectorized since the load c[i] is casted as i64 and the store c[i] is double. The loop access analysis gives up since they are in different types.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Since these two memory operations are in the same size, I believe the loop access analysis should return forward dependence and thus the loop can be vectorized.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any comments?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Jin<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">#define N 1000<o:p></o:p></p>
<p class="MsoNormal">double a[N], b[N],c[N];<o:p></o:p></p>
<p class="MsoNormal">void foo() {<o:p></o:p></p>
<p class="MsoNormal">for (int i=0;i<N;i++) {<o:p></o:p></p>
<p class="MsoNormal">b[i] =c[i];<o:p></o:p></p>
<p class="MsoNormal">c[i]=0.0;<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">for.body: ; preds = %for.body, %entry<o:p></o:p></p>
<p class="MsoNormal"> %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]<o:p></o:p></p>
<p class="MsoNormal"> %arrayidx = getelementptr inbounds [1000 x double], [1000 x double]* @c, i64 0, i64 %indvars.iv<o:p></o:p></p>
<p class="MsoNormal"> %0 = bitcast double* %arrayidx to i64*<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#0070C0"> %1 = load i64, i64* %0, align 8, !tbaa !1<o:p></o:p></span></p>
<p class="MsoNormal"> %arrayidx2 = getelementptr inbounds [1000 x double], [1000 x double]* @b, i64 0, i64 %indvars.iv<o:p></o:p></p>
<p class="MsoNormal"> %2 = bitcast double* %arrayidx2 to i64*<o:p></o:p></p>
<p class="MsoNormal"> store i64 %1, i64* %2, align 8, !tbaa !1<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#C00000"> store double 0.000000e+00, double* %arrayidx, align 8, !tbaa !1<o:p></o:p></span></p>
<p class="MsoNormal"> %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1<o:p></o:p></p>
<p class="MsoNormal"> %exitcond = icmp eq i64 %indvars.iv.next, 1000<o:p></o:p></p>
<p class="MsoNormal"> br i1 %exitcond, label %for.cond.cleanup, label %for.body<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">LAA: Found a loop in foo: loop.17<o:p></o:p></p>
<p class="MsoNormal">LAA: Processing memory accesses...<o:p></o:p></p>
<p class="MsoNormal"> AST: Alias Set Tracker: 2 alias sets for 3 pointer values.<o:p></o:p></p>
<p class="MsoNormal"> AliasSet[0x9508b80, 1] must alias, No access Pointers: (<4 x i64>* %1, 18446744073709551615)<o:p></o:p></p>
<p class="MsoNormal"> AliasSet[0x95f8a70, 2] must alias, No access Pointers: (<4 x double>* %2, 18446744073709551615), (<4 x i64>* %0, 18446744073709551615)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">LAA: Accesses(3):<o:p></o:p></p>
<p class="MsoNormal"> %1 = bitcast double* %arrayIdx11 to <4 x i64>* (write)<o:p></o:p></p>
<p class="MsoNormal"> %2 = bitcast double* %arrayIdx to <4 x double>* (write)<o:p></o:p></p>
<p class="MsoNormal"> %0 = bitcast double* %arrayIdx to <4 x i64>* (read-only)<o:p></o:p></p>
<p class="MsoNormal">Underlying objects for pointer %1 = bitcast double* %arrayIdx11 to <4 x i64>*<o:p></o:p></p>
<p class="MsoNormal"> @b = common local_unnamed_addr global [1000 x double] zeroinitializer, align 16<o:p></o:p></p>
<p class="MsoNormal">Underlying objects for pointer %2 = bitcast double* %arrayIdx to <4 x double>*<o:p></o:p></p>
<p class="MsoNormal"> @c = common local_unnamed_addr global [1000 x double] zeroinitializer, align 16<o:p></o:p></p>
<p class="MsoNormal">Underlying objects for pointer %0 = bitcast double* %arrayIdx to <4 x i64>*<o:p></o:p></p>
<p class="MsoNormal"> @c = common local_unnamed_addr global [1000 x double] zeroinitializer, align 16<o:p></o:p></p>
<p class="MsoNormal">LAA: Found a runtime check ptr: %1 = bitcast double* %arrayIdx11 to <4 x i64>*<o:p></o:p></p>
<p class="MsoNormal">LAA: Found a runtime check ptr: %2 = bitcast double* %arrayIdx to <4 x double>*<o:p></o:p></p>
<p class="MsoNormal">LAA: Found a runtime check ptr: %0 = bitcast double* %arrayIdx to <4 x i64>*<o:p></o:p></p>
<p class="MsoNormal">LAA: We need to do 0 pointer comparisons.<o:p></o:p></p>
<p class="MsoNormal">LAA: We can perform a memory runtime check if needed.<o:p></o:p></p>
<p class="MsoNormal">LAA: Checking memory dependencies<o:p></o:p></p>
<p class="MsoNormal">LAA: Src Scev: {@c,+,32}<nsw><%loop.17>Sink Scev: {@c,+,32}<nsw><%loop.17>(Induction step: 1)<o:p></o:p></p>
<p class="MsoNormal">LAA: Distance for %gepload = load <4 x i64>, <4 x i64>* %0, align 16, !tbaa !1 to store <4 x double> zeroinitializer, <4 x double>* %2, align 16, !tbaa !1: 0<o:p></o:p></p>
<p class="MsoNormal">LAA: Zero dependence difference but different types<o:p></o:p></p>
<p class="MsoNormal">Total Dependences: 1<o:p></o:p></p>
<p class="MsoNormal">LAA: unsafe dependent memory operations in loop<o:p></o:p></p>
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