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[PPCGCodeGeneration] Skip arrays with empty extent. 

Invariant load hoisted scalars, and arrays whose size we can statically compute
to be 0 do not need to be allocated as arrays.

Invariant load hoisted scalars are sent to the kernel directly as parameters.

Earlier, we used to allocate `0` bytes of memory for these because our
computation of size from `PPCGCodeGeneration::getArraySize` would result in `0`.

Now, since we don't invariant loads as arrays in PPCGCodeGeneration, this
problem does not occur anymore.

Differential Revision: https://reviews.llvm.org/D35795

llvm-svn: 308971
This commit is contained in:
Siddharth Bhat 2017-07-25 12:35:36 +00:00
parent e4130d52da
commit 43f178bbc9
2 changed files with 103 additions and 4 deletions
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23
polly/lib/CodeGen/PPCGCodeGeneration.cpp
View File

@ -2714,9 +2714,10 @@ public:
/// Create the arrays for @p PPCGProg.
///
/// @param PPCGProg The program to compute the arrays for.
void createArrays(gpu_prog *PPCGProg) {
void createArrays(gpu_prog *PPCGProg,
const SmallVector<ScopArrayInfo *, 4> &ValidSAIs) {
int i = 0;
for (auto &Array : S->arrays()) {
for (auto &Array : ValidSAIs) {
std::string TypeName;
raw_string_ostream OS(TypeName);
@ -2800,11 +2801,25 @@ public:
isl_union_map_empty(isl_set_get_space(PPCGScop->context));
PPCGProg->n_stmts = std::distance(S->begin(), S->end());
PPCGProg->stmts = getStatements();
PPCGProg->n_array = std::distance(S->array_begin(), S->array_end());
// Only consider arrays that have a non-empty extent.
// Otherwise, this will cause us to consider the following kinds of
// empty arrays:
// 1. Invariant loads that are represented by SAI objects.
// 2. Arrays with statically known zero size.
auto ValidSAIsRange =
make_filter_range(S->arrays(), [this](ScopArrayInfo *SAI) -> bool {
return !isl::manage(getExtent(SAI)).is_empty();
});
SmallVector<ScopArrayInfo *, 4> ValidSAIs(ValidSAIsRange.begin(),
ValidSAIsRange.end());
PPCGProg->n_array =
ValidSAIs.size(); // std::distance(S->array_begin(), S->array_end());
PPCGProg->array = isl_calloc_array(S->getIslCtx(), struct gpu_array_info,
PPCGProg->n_array);
createArrays(PPCGProg);
createArrays(PPCGProg, ValidSAIs);
PPCGProg->may_persist = compute_may_persist(PPCGProg);
return PPCGProg;

84
polly/test/GPGPU/invariant-load-of-scalar.ll Normal file
View File

@ -0,0 +1,84 @@
; RUN: opt %loadPolly -polly-scops -polly-invariant-load-hoisting \
; RUN: -analyze < %s | \
; RUN: FileCheck -check-prefix=SCOP %s
; RUN: opt %loadPolly -polly-codegen-ppcg -polly-invariant-load-hoisting \
; RUN: -S < %s | \
; RUN: FileCheck -check-prefix=HOST-IR %s
; RUN: opt %loadPolly -polly-codegen-ppcg -polly-invariant-load-hoisting \
; RUN: -disable-output -polly-acc-dump-kernel-ir < %s | \
; RUN: FileCheck -check-prefix=KERNEL-IR %s
; REQUIRES: pollyacc
; Check that we offload invariant loads of scalars correctly.
; Check that invariant loads are present.
; SCOP: Function: checkPrivatization
; SCOP-NEXT: Region: %entry.split---%for.end
; SCOP-NEXT: Max Loop Depth: 1
; SCOP-NEXT: Invariant Accesses: {
; SCOP-NEXT: ReadAccess := [Reduction Type: NONE] [Scalar: 0]
; SCOP-NEXT: [tmp, tmp2] -> { Stmt_entry_split[] -> MemRef_begin[0] };
; SCOP-NEXT: Execution Context: [tmp, tmp2] -> { : }
; SCOP-NEXT: ReadAccess := [Reduction Type: NONE] [Scalar: 0]
; SCOP-NEXT: [tmp, tmp2] -> { Stmt_for_body[i0] -> MemRef_end[0] };
; SCOP-NEXT: Execution Context: [tmp, tmp2] -> { : }
; SCOP-NEXT: }
;
; Check that we do not actually allocate arrays for %begin, %end, since they are
; invariant load hoisted.
; HOST-IR: %p_dev_array_MemRef_A = call i8* @polly_allocateMemoryForDevice(i64 %35)
; HOST-IR-NOT: call i8* @polly_allocateMemoryForDevice
; Check that we send the invariant loaded scalars as parameters to the
; kernel function.
; KERNEL-IR: define ptx_kernel void @FUNC_checkPrivatization_SCOP_0_KERNEL_0
; KERNEL-IR-SAME: (i8 addrspace(1)* %MemRef_A, i32 %tmp,
; KERNEL-IR-SAME: i32 %tmp2, i32 %polly.access.begin.load,
; KERNEL-IR-SAME: i32 %polly.access.end.load)
; void checkScalarPointerOffload(int A[], int *begin, int *end) {
; for(int i = *begin; i < *end; i++) {
; A[i] = 10;
; }
; }
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.12.0"
define void @checkPrivatization(i32* %A, i32* %begin, i32* %end) {
entry:
br label %entry.split
entry.split: ; preds = %entry
%tmp = load i32, i32* %begin, align 4
%tmp21 = load i32, i32* %end, align 4
%cmp3 = icmp slt i32 %tmp, %tmp21
br i1 %cmp3, label %for.body.lr.ph, label %for.end
for.body.lr.ph: ; preds = %entry.split
%tmp1 = sext i32 %tmp to i64
br label %for.body
for.body: ; preds = %for.body.lr.ph, %for.body
%indvars.iv4 = phi i64 [ %tmp1, %for.body.lr.ph ], [ %indvars.iv.next, %for.body ]
%arrayidx = getelementptr inbounds i32, i32* %A, i64 %indvars.iv4
store i32 10, i32* %arrayidx, align 4
%indvars.iv.next = add i64 %indvars.iv4, 1
%tmp2 = load i32, i32* %end, align 4
%tmp3 = sext i32 %tmp2 to i64
%cmp = icmp slt i64 %indvars.iv.next, %tmp3
br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
for.cond.for.end_crit_edge: ; preds = %for.body
br label %for.end
for.end: ; preds = %for.cond.for.end_crit_edge, %entry.split
ret void
}