Re-land r335297 "[X86] Implement more of x86-64 large and medium PIC code models"

The large code model allows code and data segments to exceed 2GB, which
means that some symbol references may require a displacement that cannot
be encoded as a displacement from RIP. The large PIC model even relaxes
the assumption that the GOT itself is within 2GB of all code. Therefore,
we need a special code sequence to materialize it:
  .LtmpN:
    leaq .LtmpN(%rip), %rbx
    movabsq $_GLOBAL_OFFSET_TABLE_-.LtmpN, %rax # Scratch
    addq %rax, %rbx # GOT base reg

From that, non-local references go through the GOT base register instead
of being PC-relative loads. Local references typically use GOTOFF
symbols, like this:
    movq extern_gv@GOT(%rbx), %rax
    movq local_gv@GOTOFF(%rbx), %rax

All calls end up being indirect:
    movabsq $local_fn@GOTOFF, %rax
    addq %rbx, %rax
    callq *%rax

The medium code model retains the assumption that the code segment is
less than 2GB, so calls are once again direct, and the RIP-relative
loads can be used to access the GOT. Materializing the GOT is easy:
    leaq _GLOBAL_OFFSET_TABLE_(%rip), %rbx # GOT base reg

DSO local data accesses will use it:
    movq local_gv@GOTOFF(%rbx), %rax

Non-local data accesses will use RIP-relative addressing, which means we
may not always need to materialize the GOT base:
    movq extern_gv@GOTPCREL(%rip), %rax

Direct calls are basically the same as they are in the small code model:
They use direct, PC-relative addressing, and the PLT is used for calls
to non-local functions.

This patch adds reasonably comprehensive testing of LEA, but there are
lots of interesting folding opportunities that are unimplemented.

I restricted the MCJIT/eh-lg-pic.ll test to Linux, since the large PIC
code model is not implemented for MachO yet.

Differential Revision: https://reviews.llvm.org/D47211

llvm-svn: 335508

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/test/ExecutionEngine/MCJIT/eh-lg-pic.ll b/llvm/test/ExecutionEngine/MCJIT/eh-lg-pic.ll
index b5b9d5409c5..4dd9d2eeac1 100644
--- a/llvm/test/ExecutionEngine/MCJIT/eh-lg-pic.ll
+++ b/llvm/test/ExecutionEngine/MCJIT/eh-lg-pic.ll
@@ -1,6 +1,6 @@
-; REQUIRES: cxx-shared-library
+; REQUIRES: cxx-shared-library, system-linux
 ; RUN: %lli -relocation-model=pic -code-model=large %s
-; XFAIL: cygwin, win32, mingw, mips-, mipsel-, i686, i386, aarch64, arm
+; XFAIL: mips-, mipsel-, i686, i386, aarch64, arm
 declare i8* @__cxa_allocate_exception(i64)
 declare void @__cxa_throw(i8*, i8*, i8*)
 declare i32 @__gxx_personality_v0(...)
@@ -15,8 +15,14 @@ define void @throwException() {
   unreachable
 }
 
+; Make an internal function so we exercise R_X86_64_GOTOFF64 relocations.
+define internal dso_local void @use_gotoff() {
+  ret void
+}
+
 define i32 @main() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
 entry:
+  call void @use_gotoff()
   invoke void @throwException()
           to label %try.cont unwind label %lpad