[polly] r295415 - [ScopInfo] Do not try to fold array dimensions of size zero

[Tobias Grosser via llvm-commits]

Author: grosser
Date: Thu Feb 16 22:48:52 2017
New Revision: 295415

URL: http://llvm.org/viewvc/llvm-project?rev=295415&view=rev
Log:
[ScopInfo] Do not try to fold array dimensions of size zero

Trying to fold such kind of dimensions will result in a division by zero,
which crashes the compiler. As such arrays are likely to invalidate the
scop anyhow (but are not illegal in LLVM-IR), there is no point in trying
to optimize the array layout. Hence, we just avoid the folding of
constant dimensions of size zero.

Added:
    polly/trunk/test/ScopInfo/multidim_fold_constant_dim_zero.ll
Modified:
    polly/trunk/lib/Analysis/ScopInfo.cpp

Modified: polly/trunk/lib/Analysis/ScopInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Analysis/ScopInfo.cpp?rev=295415&r1=295414&r2=295415&view=diff
==============================================================================
--- polly/trunk/lib/Analysis/ScopInfo.cpp (original)
+++ polly/trunk/lib/Analysis/ScopInfo.cpp Thu Feb 16 22:48:52 2017
@@ -377,6 +377,10 @@ void MemoryAccess::wrapConstantDimension
     if (!DimSizeCst)
       continue;
 
+    // This transformation is not applicable to dimensions of size zero.
+    if (DimSize->isZero())
+      continue;
+
     auto *DimSizeVal = isl_valFromAPInt(Ctx, DimSizeCst->getAPInt(), false);
     auto *Var = isl_aff_var_on_domain(isl_local_space_copy(LArraySpace),
                                       isl_dim_set, i);

Added: polly/trunk/test/ScopInfo/multidim_fold_constant_dim_zero.ll
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/multidim_fold_constant_dim_zero.ll?rev=295415&view=auto
==============================================================================
--- polly/trunk/test/ScopInfo/multidim_fold_constant_dim_zero.ll (added)
+++ polly/trunk/test/ScopInfo/multidim_fold_constant_dim_zero.ll Thu Feb 16 22:48:52 2017
@@ -0,0 +1,59 @@
+; RUN: opt %loadPolly -polly-scops -analyze -debug -S < %s 2>&1 | FileCheck %s
+
+; REQUIRES: asserts
+
+; This test case at some point crashed Polly due to a 'division by zero'
+; when trying to fold the constant dimension into outer dimension.
+; We verify that this scop is detected without crash. We also test the
+; output to undertand that the scop has been analyzed, but has also been
+; invalidated due to the zero size dimension.
+
+; CHECK: Assumed Context:
+; CHECK-NEXT: {  : 1 = 0 }
+; CHECK-NEXT: Invalid Context:
+; CHECK-NEXT: {  : 1 = 0 }
+; CHECK-NEXT: Arrays {
+; CHECK-NEXT:     i8 MemRef_arg[*][0]; // Element size 1
+; CHECK-NEXT: }
+; CHECK-NEXT: Arrays (Bounds as pw_affs) {
+; CHECK-NEXT:     i8 MemRef_arg[*][ { [] -> [(0)] } ]; // Element size 1
+; CHECK-NEXT: }
+; CHECK-NEXT: Alias Groups (0):
+; CHECK-NEXT:     n/a
+; CHECK-NEXT: Statements {
+; CHECK-NEXT: 	Stmt_bb2
+; CHECK-NEXT:         Domain :=
+; CHECK-NEXT:             { Stmt_bb2[] };
+; CHECK-NEXT:         Schedule :=
+; CHECK-NEXT:             { Stmt_bb2[] -> [] };
+; CHECK-NEXT:         MustWriteAccess :=	[Reduction Type: NONE] [Scalar: 0]
+; CHECK-NEXT:             { Stmt_bb2[] -> MemRef_arg[0, 0] };
+; CHECK-NEXT:         MustWriteAccess :=	[Reduction Type: NONE] [Scalar: 0]
+; CHECK-NEXT:             { Stmt_bb2[] -> MemRef_arg[o0, o1] : 1 = 0 };
+; CHECK-NEXT: }
+
+target datalayout = "e-p:64:64:64-S128-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f16:16:16-f32:32:32-f64:64:64-f128:128:128-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+
+declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i32, i1) #0
+
+define void @hoge([0 x [0 x i8]]* noalias %arg) {
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb5, %bb
+  br i1 false, label %bb5, label %bb2
+
+bb2:                                              ; preds = %bb1
+  %tmp = getelementptr [0 x [0 x i8]], [0 x [0 x i8]]* %arg, i64 0, i64 0, i64 0
+  store i8 32, i8* %tmp, align 1
+  %tmp3 = getelementptr [0 x [0 x i8]], [0 x [0 x i8]]* %arg, i64 0, i64 0, i64 0
+  %tmp4 = getelementptr i8, i8* %tmp3, i64 1
+  tail call void @llvm.memset.p0i8.i64(i8* %tmp4, i8 32, i64 0, i32 1, i1 false)
+  br label %bb5
+
+bb5:                                              ; preds = %bb2, %bb1
+  br i1 undef, label %bb6, label %bb1
+
+bb6:                                              ; preds = %bb5
+  ret void
+}