Allow {e,r}bp as the target of {read,write}_register.

This patch allows the read_register and write_register intrinsics to
read/write the RBP/EBP registers on X86 iff the targeted register is
the frame pointer for the containing function.

Differential Revision: http://reviews.llvm.org/D10977

llvm-svn: 241827

2 files changed, 42 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/frameregister.ll b/llvm/test/CodeGen/X86/frameregister.ll
new file mode 100644
index 00000000000..826bb9d78c9
--- /dev/null
+++ b/llvm/test/CodeGen/X86/frameregister.ll
@@ -0,0 +1,30 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin  | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-linux-gnueabi | FileCheck %s
+; RUN: opt < %s -O3 -S -mtriple=x86_64-linux-gnueabi | FileCheck %s --check-prefix=OPT
+
+define i64 @get_frame() #0 {
+entry:
+; CHECK-LABEL: get_frame:
+; CHECK: movq	%rbp, %rax
+  %sp = call i64 @llvm.read_register.i64(metadata !0)
+; OPT: @llvm.read_register.i64
+  ret i64 %sp
+}
+
+define void @set_frame(i64 %val) #0 {
+entry:
+; CHECK-LABEL: set_frame:
+; CHECK: movq	%rdi, %rbp
+  call void @llvm.write_register.i64(metadata !0, i64 %val)
+; OPT: @llvm.write_register.i64
+  ret void
+}
+
+declare i64 @llvm.read_register.i64(metadata) nounwind
+declare void @llvm.write_register.i64(metadata, i64) nounwind
+
+; register unsigned long current_stack_pointer asm("rbp");
+; CHECK-NOT: .asciz  "rbp"
+!0 = !{!"rbp\00"}
+
+attributes #0 = { nounwind "no-frame-pointer-elim"="true" }
diff --git a/llvm/test/CodeGen/X86/read-fp-no-frame-pointer.ll b/llvm/test/CodeGen/X86/read-fp-no-frame-pointer.ll
new file mode 100644
index 00000000000..9f78c294ce8
--- /dev/null
+++ b/llvm/test/CodeGen/X86/read-fp-no-frame-pointer.ll
@@ -0,0 +1,12 @@
+; RUN: not llc < %s -mtriple=x86_64-linux-gnueabi 2>&1 | FileCheck %s
+
+define i32 @get_frame() nounwind {
+entry:
+; CHECK: register ebp is allocatable: function has no frame pointer
+  %fp = call i32 @llvm.read_register.i32(metadata !0)
+  ret i32 %fp
+}
+
+declare i32 @llvm.read_register.i32(metadata) nounwind
+
+!0 = !{!"ebp\00"}