[PATCH] D9653: [PATCH 1/2] Add a "probe-stack" attribute

[John Kåre Alsaker via llvm-commits]

Zoxc updated this revision to Diff 31607.
Zoxc added a comment.

Added documentation.


http://reviews.llvm.org/D9653

Files:
  docs/LangRef.rst
  lib/Transforms/IPO/Inliner.cpp
  test/Transforms/Inline/inline-probe-stack.ll

Index: test/Transforms/Inline/inline-probe-stack.ll
===================================================================
--- /dev/null
+++ test/Transforms/Inline/inline-probe-stack.ll
@@ -0,0 +1,12 @@
+; RUN: opt %s -inline -S | FileCheck %s
+
+define internal void @inner() "probe-stack" {
+  ret void
+}
+
+define void @outer() {
+  call void @inner()
+  ret void
+}
+; CHECK: define void @outer() #0
+; CHECK: attributes #0 = { "probe-stack" }
Index: lib/Transforms/IPO/Inliner.cpp
===================================================================
--- lib/Transforms/IPO/Inliner.cpp
+++ lib/Transforms/IPO/Inliner.cpp
@@ -139,6 +139,12 @@
 
   AdjustCallerSSPLevel(Caller, Callee);
 
+  // If the callee requires stack probes, we ensure that the caller will
+  // require those too
+  if (Callee->hasFnAttribute("probe-stack")) {
+    Caller->addFnAttr("probe-stack");
+  }
+
   // Look at all of the allocas that we inlined through this call site.  If we
   // have already inlined other allocas through other calls into this function,
   // then we know that they have disjoint lifetimes and that we can merge them.
Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -1302,6 +1302,15 @@
     passes make choices that keep the code size of this function low,
     and otherwise do optimizations specifically to reduce code size as
     long as they do not significantly impact runtime performance.
+``"probe-stack"``
+    This attribute indicates that the function will trigger a guard region
+    in the end of the stack. It ensures that accesses to the stack must be
+    no further apart than the size of the guard region to a previous
+    access of the stack.
+
+    If a function that has a ``"probe-stack"`` attribute is inlined into a
+    function that doesn't have a ``"probe-stack"`` attribute, then the
+    resulting function will have a ``"probe-stack"`` attribute.
 ``readnone``
     On a function, this attribute indicates that the function computes its
     result (or decides to unwind an exception) based strictly on its arguments,


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