[CodeGen] Emit a helper function for __builtin_os_log_format to reduce

code size.

Currently clang expands a call to __builtin_os_log_format into a long
sequence of instructions at the call site, causing code size to
increase in some cases.

This commit attempts to reduce code size by emitting a helper function
that can be shared by calls to __builtin_os_log_format with similar
formats and arguments. The helper function has linkonce_odr linkage to
enable the linker to merge identical functions across translation units.
Attribute 'noinline' is attached to the helper function at -Oz so that
the inliner doesn't inline functions that can potentially be merged.

This commit also fixes a bug where the generated IR writes past the end
of the buffer when "%m" is the last specifier appearing in the format
string passed to __builtin_os_log_format.

Original patch by Duncan Exon Smith.

rdar://problem/34065973
rdar://problem/34196543

Differential Revision: https://reviews.llvm.org/D38606

llvm-svn: 315045

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 50c8ebf..8cee6b6 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -76,6 +76,10 @@ class ObjCAtThrowStmt;
 class ObjCAtSynchronizedStmt;
 class ObjCAutoreleasePoolStmt;
 
+namespace analyze_os_log {
+class OSLogBufferLayout;
+}
+
 namespace CodeGen {
 class CodeGenTypes;
 class CGCallee;
@@ -3304,6 +3308,13 @@ public:
                          unsigned BuiltinID, const CallExpr *E,
                          ReturnValueSlot ReturnValue);
 
+  /// Emit IR for __builtin_os_log_format.
+  RValue emitBuiltinOSLogFormat(const CallExpr &E);
+
+  llvm::Function *generateBuiltinOSLogHelperFunction(
+      const analyze_os_log::OSLogBufferLayout &Layout,
+      CharUnits BufferAlignment);
+
   RValue EmitBlockCallExpr(const CallExpr *E, ReturnValueSlot ReturnValue);
 
   /// EmitTargetBuiltinExpr - Emit the given builtin call. Returns 0 if the call