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| author | Chandler Carruth <chandlerc@gmail.com> | 2012-04-09 02:13:06 +0000 |
|---|---|---|
| committer | Chandler Carruth <chandlerc@gmail.com> | 2012-04-09 02:13:06 +0000 |
| commit | ab5a55e11870c8f5aaa8e4b973092bf66f9d6742 (patch) | |
| tree | 070aad9783c1f9d9e8efa514f8fab0bbb84e2f47 /test/CodeGen/X86/tls-pie.ll | |
| parent | 6916a2375a210e3c60a599b9f1f8c13f38455a9b (diff) | |
| download | llvm-ab5a55e11870c8f5aaa8e4b973092bf66f9d6742.tar.gz llvm-ab5a55e11870c8f5aaa8e4b973092bf66f9d6742.tar.bz2 llvm-ab5a55e11870c8f5aaa8e4b973092bf66f9d6742.tar.xz | |
Cleanup and relax a restriction on the matching of global offsets into
x86 addressing modes. This allows PIE-based TLS offsets to fit directly
into an addressing mode immediate offset, which is the last remaining
code quality issue from PR12380. With this patch, that PR is completely
fixed.
To understand why this patch is correct to match these offsets into
addressing mode immediates, break it down by cases:
1) 32-bit is trivially correct, and unmodified here.
2) 64-bit non-small mode is unchanged and never matches.
3) 64-bit small PIC code which is RIP-relative is handled specially in
the match to try to fit RIP into the base register. If it fails, it
now early exits. This behavior is unchanged by the patch.
4) 64-bit small non-PIC code which is not RIP-relative continues to work
as it did before. The reason these immediates are safe is because the
ABI ensures they fit in small mode. This behavior is unchanged.
5) 64-bit small PIC code which is *not* using RIP-relative addressing.
This is the only case changed by the patch, and the primary place you
see it is in TLS, either the win64 section offset TLS or Linux
local-exec TLS model in a PIC compilation. Here the ABI again ensures
that the immediates fit because we are in small mode, and any other
operations required due to the PIC relocation model have been handled
externally to the Wrapper node (extra loads etc are made around the
wrapper node in ISelLowering).
I've tested this as much as I can comparing it with GCC's output, and
everything appears safe. I discussed this with Anton and it made sense
to him at least at face value. That said, if there are issues with PIC
code after this patch, yell and we can revert it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154304 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/CodeGen/X86/tls-pie.ll')
| -rw-r--r-- | test/CodeGen/X86/tls-pie.ll | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/test/CodeGen/X86/tls-pie.ll b/test/CodeGen/X86/tls-pie.ll index 6c739cbabd..e2e58a541a 100644 --- a/test/CodeGen/X86/tls-pie.ll +++ b/test/CodeGen/X86/tls-pie.ll @@ -11,8 +11,7 @@ define i32 @f1() { ; X32: movl %gs:i@NTPOFF, %eax ; X32-NEXT: ret ; X64: f1: -; X64: movabsq $i@TPOFF, %rax -; X64-NEXT: movl %fs:(%rax), %eax +; X64: movl %fs:i@TPOFF, %eax ; X64-NEXT: ret entry: @@ -27,7 +26,7 @@ define i32* @f2() { ; X32-NEXT: ret ; X64: f2: ; X64: movq %fs:0, %rax -; X64-NEXT: addq $i@TPOFF, %rax +; X64-NEXT: leaq i@TPOFF(%rax), %rax ; X64-NEXT: ret entry: |