DebugInfo: Blocks: Do not depend on LLVM argument numbering when choosing the debug info argument numbering.

Due to the possible presence of return-by-out parameters, using the LLVM
argument number count when numbering debug info arguments can end up
off-by-one. This could produce two arguments with the same number, which
would in turn cause LLVM to emit only one of those arguments (whichever
it found last) or assert (r215157).

llvm-svn: 215227

1 files changed, 25 insertions, 0 deletions

diff --git a/clang/test/CodeGen/debug-info-block-out-return.c b/clang/test/CodeGen/debug-info-block-out-return.c
new file mode 100644
index 00000000000..da84df8f11c
--- /dev/null
+++ b/clang/test/CodeGen/debug-info-block-out-return.c
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -g -fblocks -emit-llvm -o - %s | FileCheck %s
+
+// Check that arg numbering is not affected by LLVM IR argument numbering -
+// since the latter is affected by return-by-out-parameter ABI requirements
+
+// 1 for the argument number (1 indexed), 2 for the line number
+// 16777218 == 1 << 24 | 2
+// 33554434 == 2 << 24 | 2
+// This explains the two magic numbers below, testing that these two arguments
+// are numbered correctly. If they are not numbered correctly they may appear
+// out of order or not at all (the latter would occur if they were both assigned
+// the same argument number by mistake).
+
+// CHECK: metadata !".block_descriptor", metadata !{{[0-9]*}}, i32 16777218, {{.*}} ; [ DW_TAG_arg_variable ] [.block_descriptor]
+// CHECK: metadata !"param", metadata !{{[0-9]*}}, i32 33554434, {{.*}} ; [ DW_TAG_arg_variable ] [param]
+
+// Line directive so we don't have to worry about how many lines preceed the
+// test code (as the line number is mangled in with the argument number as shown
+// above)
+#line 1
+typedef struct { int array[12]; } BigStruct_t;
+BigStruct_t (^a)() = ^(int param) {
+    BigStruct_t b;
+    return b;
+};