AArch64: implement large code model access to global variables.

The MOVZ/MOVK instruction sequence may not be the most efficient (a
literal-pool load could be better) but adding that would require
reinstating the ConstantIslands pass.

For now the sequence is correct, and that's enough. Beware, as of
commit GNU ld does not appear to support the relocations needed for
this. Its primary purpose (for now) will be to support JITed code,
since in that case there is no guarantee of where your code will end
up in memory relative to external symbols it references.

llvm-svn: 181117

1 files changed, 61 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AArch64/code-model-large-abs.ll b/llvm/test/CodeGen/AArch64/code-model-large-abs.ll
new file mode 100644
index 00000000000..a365568e11e
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/code-model-large-abs.ll
@@ -0,0 +1,61 @@
+; RUN: llc -mtriple=aarch64-none-linux-gnu -code-model=large < %s | FileCheck %s
+
+@var8 = global i8 0
+@var16 = global i16 0
+@var32 = global i32 0
+@var64 = global i64 0
+
+define i8* @global_addr() {
+; CHECK: global_addr:
+  ret i8* @var8
+  ; The movz/movk calculation should end up returned directly in x0.
+; CHECK: movz x0, #:abs_g3:var8
+; CHECK: movk x0, #:abs_g2_nc:var8
+; CHECK: movk x0, #:abs_g1_nc:var8
+; CHECK: movk x0, #:abs_g0_nc:var8
+; CHECK-NEXT: ret
+}
+
+define i8 @global_i8() {
+; CHECK: global_i8:
+  %val = load i8* @var8
+  ret i8 %val
+; CHECK: movz x[[ADDR_REG:[0-9]+]], #:abs_g3:var8
+; CHECK: movk x[[ADDR_REG]], #:abs_g2_nc:var8
+; CHECK: movk x[[ADDR_REG]], #:abs_g1_nc:var8
+; CHECK: movk x[[ADDR_REG]], #:abs_g0_nc:var8
+; CHECK: ldrb w0, [x[[ADDR_REG]]]
+}
+
+define i16 @global_i16() {
+; CHECK: global_i16:
+  %val = load i16* @var16
+  ret i16 %val
+; CHECK: movz x[[ADDR_REG:[0-9]+]], #:abs_g3:var16
+; CHECK: movk x[[ADDR_REG]], #:abs_g2_nc:var16
+; CHECK: movk x[[ADDR_REG]], #:abs_g1_nc:var16
+; CHECK: movk x[[ADDR_REG]], #:abs_g0_nc:var16
+; CHECK: ldrh w0, [x[[ADDR_REG]]]
+}
+
+define i32 @global_i32() {
+; CHECK: global_i32:
+  %val = load i32* @var32
+  ret i32 %val
+; CHECK: movz x[[ADDR_REG:[0-9]+]], #:abs_g3:var32
+; CHECK: movk x[[ADDR_REG]], #:abs_g2_nc:var32
+; CHECK: movk x[[ADDR_REG]], #:abs_g1_nc:var32
+; CHECK: movk x[[ADDR_REG]], #:abs_g0_nc:var32
+; CHECK: ldr w0, [x[[ADDR_REG]]]
+}
+
+define i64 @global_i64() {
+; CHECK: global_i64:
+  %val = load i64* @var64
+  ret i64 %val
+; CHECK: movz x[[ADDR_REG:[0-9]+]], #:abs_g3:var64
+; CHECK: movk x[[ADDR_REG]], #:abs_g2_nc:var64
+; CHECK: movk x[[ADDR_REG]], #:abs_g1_nc:var64
+; CHECK: movk x[[ADDR_REG]], #:abs_g0_nc:var64
+; CHECK: ldr x0, [x[[ADDR_REG]]]
+}