New llc option pie-copy-relocations to optimize access to extern globals.

This option indicates copy relocations support is available from the linker
when building as PIE and allows accesses to extern globals to avoid the GOT.

Differential Revision: https://reviews.llvm.org/D24849

llvm-svn: 284160

1 files changed, 119 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/global-access-pie-copyrelocs.ll b/llvm/test/CodeGen/X86/global-access-pie-copyrelocs.ll
new file mode 100644
index 00000000000..5c4a87c969c
--- /dev/null
+++ b/llvm/test/CodeGen/X86/global-access-pie-copyrelocs.ll
@@ -0,0 +1,119 @@
+; RUN: llc < %s -march=x86-64 -mcpu=generic -mtriple=x86_64-linux-gnu -relocation-model=pic -pie-copy-relocations \
+; RUN:   | FileCheck -check-prefix=X64 %s
+; RUN: llc < %s -emulated-tls -march=x86 -mcpu=generic -mtriple=i386-linux-gnu -relocation-model=pic -pie-copy-relocations \
+; RUN:   | FileCheck -check-prefix=X32 %s
+
+; External Linkage
+@a = global i32 0, align 4
+
+define i32 @my_access_global_a() #0 {
+; X32-LABEL: my_access_global_a:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT:  movl a@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_a:
+; X64:       movl a(%rip), %eax
+
+entry:
+  %0 = load i32, i32* @a, align 4
+  ret i32 %0
+}
+
+; WeakAny Linkage
+@b = weak global i32 0, align 4
+
+define i32 @my_access_global_b() #0 {
+; X32-LABEL: my_access_global_b:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT:  movl b@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_b:
+; X64:       movl b(%rip), %eax
+
+entry:
+  %0 = load i32, i32* @b, align 4
+  ret i32 %0
+}
+
+; Internal Linkage
+@c = internal global i32 0, align 4
+
+define i32 @my_access_global_c() #0 {
+; X32-LABEL: my_access_global_c:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT:  movl c@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_c:
+; X64:       movl c(%rip), %eax
+
+entry:
+  %0 = load i32, i32* @c, align 4
+  ret i32 %0
+}
+
+; External Linkage, only declaration.
+@d = external global i32, align 4
+
+define i32 @my_access_global_load_d() #0 {
+; X32-LABEL: my_access_global_load_d:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT:  movl d@GOTOFF(%eax), %eax
+; X64-LABEL: my_access_global_load_d:
+; X64:       movl d(%rip), %eax
+
+entry:
+  %0 = load i32, i32* @d, align 4
+  ret i32 %0
+}
+
+; External Linkage, only declaration, store a value.
+
+define i32 @my_access_global_store_d() #0 {
+; X32-LABEL: my_access_global_store_d:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %eax
+; X32-NEXT:  movl $2, d@GOTOFF(%eax)
+; X64-LABEL: my_access_global_store_d:
+; X64:  movl $2, d(%rip)
+
+entry:
+  store i32 2, i32* @d, align 4
+  ret i32 0
+}
+
+; External Linkage, function pointer access.
+declare i32 @access_fp(i32 ()*)
+declare i32 @foo()
+
+define i32 @my_access_fp_foo() #0 {
+; X32-LABEL: my_access_fp_foo:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %ebx
+; X32-NEXT:  movl	foo@GOT(%ebx), %eax
+; X64-LABEL: my_access_fp_foo:
+; X64:       movq foo@GOTPCREL(%rip), %rdi
+
+entry:
+  %call = call i32 @access_fp(i32 ()* @foo)
+  ret i32 %call
+}
+
+; LinkOnceODR Linkage, function pointer access.
+
+$bar = comdat any
+
+define linkonce_odr i32 @bar() comdat {
+entry:
+  ret i32 0
+}
+
+define i32 @my_access_fp_bar() #0 {
+; X32-LABEL: my_access_fp_bar:
+; X32:       addl $_GLOBAL_OFFSET_TABLE_{{.*}}, %ebx
+; X32-NEXT:  leal	bar@GOTOFF(%ebx), %eax
+; X64-LABEL: my_access_fp_bar:
+; X64:       leaq bar(%rip), %rdi
+
+entry:
+  %call = call i32 @access_fp(i32 ()* @bar)
+  ret i32 %call
+}
+
+!llvm.module.flags = !{!0, !1}
+!0 = !{i32 1, !"PIC Level", i32 1}
+!1 = !{i32 1, !"PIE Level", i32 1}