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[SCEV] Assume parameters coming from function calls contain IVs 

The optimistic delinearization implemented in LLVM detects array sizes by
looking for non-linear products between parameters and induction variables.
In OpenCL code, such products often look like:

  A[get_global_id(0) * N + get_global_id(1)]

Hence, the IV is hidden in the get_global_id() call and consequently
delinearization would fail as no induction variable is available that helps
us to identify N as array size parameter.

We now use a very simple heuristic to change this. We assume that each parameter
that comes directly from a function call is a hidden induction variable. As
a result, we can delinearize the access above to:

  A[get_global_id(0)][get_global_id(1]

llvm-svn: 304073
This commit is contained in:
Tobias Grosser 2017-05-27 15:17:49 +00:00
parent 33f4a97287
commit e3684d0b84
2 changed files with 84 additions and 1 deletions
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5
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -9590,8 +9590,11 @@ struct SCEVCollectAddRecMultiplies {
bool HasAddRec = false;
SmallVector<const SCEV *, 0> Operands;
for (auto Op : Mul->operands()) {
if (isa<SCEVUnknown>(Op)) {
const SCEVUnknown *Unknown = dyn_cast<SCEVUnknown>(Op);
if (Unknown && !isa<CallInst>(Unknown->getValue())) {
Operands.push_back(Op);
} else if (Unknown) {
HasAddRec = true;
} else {
bool ContainsAddRec;
SCEVHasAddRec ContiansAddRec(ContainsAddRec);

80
llvm/test/Analysis/Delinearization/constant_functions_multi_dim.ll Normal file
View File

@ -0,0 +1,80 @@
; RUN: opt -delinearize -analyze < %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
; CHECK: Inst: %tmp = load float, float* %arrayidx, align 4
; CHECK-NEXT: In Loop with Header: for.inc
; CHECK-NEXT: AccessFunction: {(4 * %N * %call),+,4}<nsw><%for.inc>
; CHECK-NEXT: Base offset: %A
; CHECK-NEXT: ArrayDecl[UnknownSize][%N] with elements of 4 bytes.
; CHECK-NEXT: ArrayRef[%call][{0,+,1}<nuw><nsw><%for.inc>]
; CHECK: Inst: %tmp5 = load float, float* %arrayidx4, align 4
; CHECK-NEXT: In Loop with Header: for.inc
; CHECK-NEXT: AccessFunction: {(4 * %call1),+,(4 * %N)}<nsw><%for.inc>
; CHECK-NEXT: Base offset: %B
; CHECK-NEXT: ArrayDecl[UnknownSize][%N] with elements of 4 bytes.
; CHECK-NEXT: ArrayRef[{0,+,1}<nuw><nsw><%for.inc>][%call1]
; Function Attrs: noinline nounwind uwtable
define void @mat_mul(float* %C, float* %A, float* %B, i64 %N) #0 !kernel_arg_addr_space !2 !kernel_arg_access_qual !3 !kernel_arg_type !4 !kernel_arg_base_type !4 !kernel_arg_type_qual !5 {
entry:
br label %entry.split
entry.split: ; preds = %entry
%call = tail call i64 @_Z13get_global_idj(i32 0) #3
%call1 = tail call i64 @_Z13get_global_idj(i32 1) #3
%cmp1 = icmp sgt i64 %N, 0
%mul = mul nsw i64 %call, %N
br i1 %cmp1, label %for.inc.lr.ph, label %for.end
for.inc.lr.ph: ; preds = %entry.split
br label %for.inc
for.inc: ; preds = %for.inc.lr.ph, %for.inc
%acc.03 = phi float [ 0.000000e+00, %for.inc.lr.ph ], [ %tmp6, %for.inc ]
%m.02 = phi i64 [ 0, %for.inc.lr.ph ], [ %inc, %for.inc ]
%add = add nsw i64 %m.02, %mul
%arrayidx = getelementptr inbounds float, float* %A, i64 %add
%tmp = load float, float* %arrayidx, align 4
%mul2 = mul nsw i64 %m.02, %N
%add3 = add nsw i64 %mul2, %call1
%arrayidx4 = getelementptr inbounds float, float* %B, i64 %add3
%tmp5 = load float, float* %arrayidx4, align 4
%tmp6 = tail call float @llvm.fmuladd.f32(float %tmp, float %tmp5, float %acc.03)
%inc = add nuw nsw i64 %m.02, 1
%exitcond = icmp ne i64 %inc, %N
br i1 %exitcond, label %for.inc, label %for.cond.for.end_crit_edge
for.cond.for.end_crit_edge: ; preds = %for.inc
%.lcssa = phi float [ %tmp6, %for.inc ]
br label %for.end
for.end: ; preds = %for.cond.for.end_crit_edge, %entry.split
%acc.0.lcssa = phi float [ %.lcssa, %for.cond.for.end_crit_edge ], [ 0.000000e+00, %entry.split ]
%add7 = add nsw i64 %mul, %call1
%arrayidx8 = getelementptr inbounds float, float* %C, i64 %add7
store float %acc.0.lcssa, float* %arrayidx8, align 4
ret void
}
; Function Attrs: nounwind readnone
declare i64 @_Z13get_global_idj(i32) #1
; Function Attrs: nounwind readnone speculatable
declare float @llvm.fmuladd.f32(float, float, float) #2
attributes #0 = { noinline nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind readnone speculatable }
attributes #3 = { nounwind readnone }
!llvm.module.flags = !{!0}
!llvm.ident = !{!1}
!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{!"clang version 5.0.0 (trunk 303846) (llvm/trunk 303834)"}
!2 = !{i32 1, i32 1, i32 1, i32 0}
!3 = !{!"none", !"none", !"none", !"none"}
!4 = !{!"float*", !"float*", !"float*", !"long"}
!5 = !{!"", !"", !"", !""}