[PATCH] D34528: Define behavior of "stack-probe-size" attribute when inlining.
whitequark via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 22 13:19:43 PDT 2017
whitequark created this revision.
Herald added subscribers: eraman, javed.absar.
Also document the attribute, since "probe-stack" already is.
Repository:
rL LLVM
https://reviews.llvm.org/D34528
Files:
docs/LangRef.rst
lib/IR/Attributes.cpp
test/Transforms/Inline/inline-stack-probe-size.ll
Index: test/Transforms/Inline/inline-stack-probe-size.ll
===================================================================
--- /dev/null
+++ test/Transforms/Inline/inline-stack-probe-size.ll
@@ -0,0 +1,29 @@
+; RUN: opt %s -inline -S | FileCheck %s
+
+define internal void @innerSmall() "stack-probe-size"="4096" {
+ ret void
+}
+
+define internal void @innerLarge() "stack-probe-size"="8192" {
+ ret void
+}
+
+define void @outerNoAttribute() {
+ call void @innerSmall()
+ ret void
+}
+
+define void @outerConflictingAttributeSmall() "stack-probe-size"="4096" {
+ call void @innerLarge()
+ ret void
+}
+
+define void @outerConflictingAttributeLarge() "stack-probe-size"="8192" {
+ call void @innerSmall()
+ ret void
+}
+
+; CHECK: define void @outerNoAttribute() #0
+; CHECK: define void @outerConflictingAttributeSmall() #0
+; CHECK: define void @outerConflictingAttributeLarge() #0
+; CHECK: attributes #0 = { "stack-probe-size"="4096" }
Index: lib/IR/Attributes.cpp
===================================================================
--- lib/IR/Attributes.cpp
+++ lib/IR/Attributes.cpp
@@ -1641,8 +1641,28 @@
/// \brief If the inlined function required stack probes, then ensure that
/// the calling function has those too.
static void adjustCallerStackProbes(Function &Caller, const Function &Callee) {
- if (!Caller.hasFnAttribute("probe-stack") && Callee.hasFnAttribute("probe-stack"))
- Caller.addFnAttr("probe-stack", Callee.getFnAttribute("probe-stack").getValueAsString());
+ if (!Caller.hasFnAttribute("probe-stack") &&
+ Callee.hasFnAttribute("probe-stack")) {
+ Caller.addFnAttr(Callee.getFnAttribute("probe-stack"));
+ }
+
+ if (Callee.hasFnAttribute("stack-probe-size")) {
+ uint64_t CalleeStackProbeSize;
+ Callee.getFnAttribute("stack-probe-size")
+ .getValueAsString()
+ .getAsInteger(0, CalleeStackProbeSize);
+ if (Caller.hasFnAttribute("stack-probe-size")) {
+ uint64_t CallerStackProbeSize;
+ Caller.getFnAttribute("stack-probe-size")
+ .getValueAsString()
+ .getAsInteger(0, CallerStackProbeSize);
+ if (CallerStackProbeSize > CalleeStackProbeSize) {
+ Caller.addFnAttr(Callee.getFnAttribute("stack-probe-size"));
+ }
+ } else {
+ Caller.addFnAttr(Callee.getFnAttribute("stack-probe-size"));
+ }
+ }
}
#define GET_ATTR_COMPAT_FUNC
Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -1511,6 +1511,20 @@
On an argument, this attribute indicates that the function does not write
through this pointer argument, even though it may write to the memory that
the pointer points to.
+``"stack-probe-size"``
+ This attribute controls the behavior of the ``"probe-stack"`` attribute.
+ It defines the size of the guard region. It ensures that if the function
+ may use more stack space than the size of the guard region, stack probing
+ sequence will be emitted. It takes one required integer value, which
+ is 4096 by default.
+
+ If a function that has a ``"stack-probe-size"`` attribute is inlined into
+ a function with another ``"stack-probe-size"`` attribute, the resulting
+ function has the ``"stack-probe-size"`` attribute that has the lower
+ numeric value. If a function that has a ``"stack-probe-size"`` attribute is
+ inlined into a function that has no ``"stack-probe-size"`` attribute
+ at all, the resulting function has the ``"stack-probe-size"`` attribute
+ of the callee.
``writeonly``
On a function, this attribute indicates that the function may write to but
does not read from memory.
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