Introduce a "patchable-function" function attribute
Summary:
The `"patchable-function"` attribute can be used by an LLVM client to
influence LLVM's code generation in ways that makes the generated code
easily patchable at runtime (for instance, to redirect control).
Right now only one patchability scheme is supported,
`"prologue-short-redirect"`, but this can be expanded in the future.
Reviewers: joker.eph, rnk, echristo, dberris
Subscribers: joker.eph, echristo, mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D19046
llvm-svn: 266715
diff --git a/llvm/test/CodeGen/X86/patchable-prologue.ll b/llvm/test/CodeGen/X86/patchable-prologue.ll
new file mode 100644
index 0000000..b04dc86
--- /dev/null
+++ b/llvm/test/CodeGen/X86/patchable-prologue.ll
@@ -0,0 +1,43 @@
+; RUN: llc -filetype=obj -o - -mtriple=x86_64-apple-macosx < %s | llvm-objdump -triple x86_64-apple-macosx -disassemble - | FileCheck %s
+; RUN: llc -mtriple=x86_64-apple-macosx < %s | FileCheck %s --check-prefix=CHECK-ALIGN
+
+declare void @callee(i64*)
+
+define void @f0() "patchable-function"="prologue-short-redirect" {
+; CHECK-LABEL: _f0:
+; CHECK-NEXT: 66 90 nop
+
+; CHECK-ALIGN: .p2align 4, 0x90
+; CHECK-ALIGN: _f0:
+
+ ret void
+}
+
+define void @f1() "patchable-function"="prologue-short-redirect" "no-frame-pointer-elim"="true" {
+; CHECK-LABEL: _f1
+; CHECK-NEXT: ff f5 pushq %rbp
+
+; CHECK-ALIGN: .p2align 4, 0x90
+; CHECK-ALIGN: _f1:
+ ret void
+}
+
+define void @f2() "patchable-function"="prologue-short-redirect" {
+; CHECK-LABEL: _f2
+; CHECK-NEXT: 48 81 ec a8 00 00 00 subq $168, %rsp
+
+; CHECK-ALIGN: .p2align 4, 0x90
+; CHECK-ALIGN: _f2:
+ %ptr = alloca i64, i32 20
+ call void @callee(i64* %ptr)
+ ret void
+}
+
+define void @f3() "patchable-function"="prologue-short-redirect" optsize {
+; CHECK-LABEL: _f3
+; CHECK-NEXT: 66 90 nop
+
+; CHECK-ALIGN: .p2align 4, 0x90
+; CHECK-ALIGN: _f3:
+ ret void
+}