Check whether IslAstInfo and DependenceInfo were computed for the same Scop.

Since -polly-codegen reports itself to preserve DependenceInfo and IslAstInfo,
we might get those analysis that were computed by a different ScopInfo for a
different Scop structure. This would be unfortunate because DependenceInfo and
IslAstInfo hold references to resources allocated by
ScopInfo/ScopBuilder/Scop (e.g. isl_id). If -polly-codegen and
DependenceInfo/IslAstInfo do not agree on which Scop to use, unpredictable
things can happen.

When the ScopInfo/Scop object is freed, there is a high probability that the
new ScopInfo/Scop object will be created at the same heap position with the
same address. Comparing whether the Scop or ScopInfo address is the expected
therefore is unreliable.

Instead, we compare the address of the isl_ctx object. Both, DependenceInfo
and IslAstInfo must hold a reference to the isl_ctx object to ensure it is
not freed before the destruction of those analyses which might happen after
the destruction of the Scop/ScopInfo they refer to.  Hence, the isl_ctx
will not be freed and its address not reused as long there is a
DependenceInfo or IslAstInfo around.

This fixes llvm.org/PR34441

llvm-svn: 313842

1 files changed, 61 insertions, 0 deletions

diff --git a/polly/test/Isl/CodeGen/multiple-codegens.ll b/polly/test/Isl/CodeGen/multiple-codegens.ll
new file mode 100644
index 00000000000..b9bfb55e041
--- /dev/null
+++ b/polly/test/Isl/CodeGen/multiple-codegens.ll
@@ -0,0 +1,61 @@
+; RUN: opt %loadPolly -polly-scops -polly-opt-isl -polly-codegen -polly-scops -polly-codegen -S < %s | FileCheck %s
+;
+; llvm.org/PR34441
+; Properly handle multiple -polly-scops/-polly-codegen in the same
+; RegionPassManager. -polly-codegen must not reuse the -polly-ast analysis the
+; was created for the first -polly-scops pass.
+; The current solution is that only the first -polly-codegen is allowed to
+; generate code, the second detects it is re-using an IslAst that belongs to a
+; different ScopInfo.
+;
+; int a, b, c;
+;
+; int main () {
+;  while (a++)
+;    while (b) {
+;        c = 0;
+;        break;
+;      }
+;  return 0;
+; }
+;
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+
+@a = common global i32 0, align 4
+@b = common global i32 0, align 4
+@c = common global i32 0, align 4
+
+; Function Attrs: nounwind uwtable
+define i32 @main() {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  %.pre = load i32, i32* @a, align 4
+  br label %while.cond
+
+while.cond:                                       ; preds = %while.end, %entry
+  %0 = phi i32 [ %inc, %while.end ], [ %.pre, %entry ]
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* @a, align 4
+  %tobool = icmp ne i32 %0, 0
+  br i1 %tobool, label %while.body, label %while.end4
+
+while.body:                                       ; preds = %while.cond
+  %1 = load i32, i32* @b, align 4
+  %tobool2 = icmp ne i32 %1, 0
+  br i1 %tobool2, label %while.body3, label %while.end
+
+while.body3:                                      ; preds = %while.body
+  store i32 0, i32* @c, align 4
+  br label %while.end
+
+while.end:                                        ; preds = %while.body3, %while.body
+  br label %while.cond
+
+while.end4:                                       ; preds = %while.cond
+  ret i32 0
+}
+
+
+; CHECK: polly.start:
+; CHECK-NOT: polly.start: