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, 2 insertions, 2 deletions

diff --git a/llvm/test/CodeGen/X86/fast-isel-call-cleanup.ll b/llvm/test/CodeGen/X86/fast-isel-call-cleanup.ll
index 27e42416ef8..1f7a59efa69 100644
--- a/llvm/test/CodeGen/X86/fast-isel-call-cleanup.ll
+++ b/llvm/test/CodeGen/X86/fast-isel-call-cleanup.ll
@@ -1,4 +1,4 @@
-; RUN: llc -fast-isel-sink-local-values -fast-isel -O0 -code-model=large -mcpu=generic -mtriple=x86_64-apple-darwin10 -relocation-model=pic < %s | FileCheck %s
+; RUN: llc -fast-isel-sink-local-values -fast-isel -O0 -code-model=large -mcpu=generic -mtriple=x86_64-linux -relocation-model=static < %s | FileCheck %s
 
 ; Check that fast-isel cleans up when it fails to lower a call instruction.
 define void @fastiselcall() {
@@ -9,7 +9,7 @@ entry:
 ; FastISel's local value code was dead, so it's gone.
 ; CHECK-NOT: movl $42,
 ; SDag-ISel's arg mov:
-; CHECK: movabsq $_targetfn, %[[REG:[^ ]*]]
+; CHECK: movabsq $targetfn, %[[REG:[^ ]*]]
 ; CHECK: movl $42, %edi
 ; CHECK: callq *%[[REG]]