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Most of the PowerPC64 code generation for the ELF ABI is already PIC. There are four main exceptions: (1) Constant pointer arrays etc. should in writeable sections. (2) The TOC restoration NOP after a call is needed for all global symbols. While GNU ld has a workaround for questionable GCC self-calls, we trigger the checks for calls from COMDAT sections as they cross input sections and are therefore not considered self-calls. The current decision is questionable and suboptimal, but outside the scope of the change. (3) TLS access can not use the initial-exec model. (4) Jump tables should use relative addresses. Note that the current encoding doesn't work for the large code model, but it is more compact than the default for any non-trivial jump table. Improving this is again beyond the scope of this change. At least (1) and (3) are assumptions made in target-independent code and introducing additional hooks is a bit messy. Testing with clang shows that a -fPIC binary is 600KB smaller than the corresponding -fno-pic build. Separate testing from improved jump table encodings would explain only about 100KB or so. The rest is expected to be a result of more aggressive immediate forming for -fno-pic, where the -fPIC binary just uses TOC entries. This change brings the LLVM output in line with the GCC output, other PPC64 compilers like XLC on AIX are known to produce PIC by default as well. The relocation model can still be provided explicitly, i.e. when using MCJIT. One test case for case (1) is included, other test cases with relocation mode sensitive behavior are wired to static for now. They will be reviewed and adjusted separately. Differential Revision: https://reviews.llvm.org/D26566 llvm-svn: 289743
89 lines
2.3 KiB
LLVM
89 lines
2.3 KiB
LLVM
; RUN: llc -relocation-model=static -verify-machineinstrs < %s -march=ppc64 -mcpu=pwr7 | FileCheck %s
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target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
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target triple = "powerpc64-unknown-linux-gnu"
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define void @foo() nounwind noinline {
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ret void
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}
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define weak void @foo_weak() nounwind {
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ret void
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}
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; Calls to local function does not require the TOC restore 'nop'
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define void @test_direct() nounwind readnone {
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; CHECK-LABEL: test_direct:
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tail call void @foo() nounwind
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; Because of tail call optimization, it can be 'b' instruction.
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; CHECK: [[BR:b[l]?]] foo
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; CHECK-NOT: nop
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ret void
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}
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; Calls to weak function requires a TOC restore 'nop' because they
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; may be overridden in a different module.
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define void @test_weak() nounwind readnone {
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; CHECK-LABEL: test_weak:
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tail call void @foo_weak() nounwind
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; CHECK: bl foo
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; CHECK-NEXT: nop
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ret void
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}
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; Indirect calls requires a full stub creation
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define void @test_indirect(void ()* nocapture %fp) nounwind {
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; CHECK-LABEL: test_indirect:
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tail call void %fp() nounwind
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; CHECK: ld [[FP:[0-9]+]], 0(3)
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; CHECK: ld 11, 16(3)
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; CHECK: ld 2, 8(3)
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; CHECK-NEXT: mtctr [[FP]]
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; CHECK-NEXT: bctrl
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; CHECK-NEXT: ld 2, 40(1)
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ret void
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}
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; Absolute values must use the regular indirect call sequence
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; The main purpose of this test is to ensure that BLA is not
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; used on 64-bit SVR4 (as e.g. on Darwin).
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define void @test_abs() nounwind {
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; CHECK-LABEL: test_abs:
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tail call void inttoptr (i64 1024 to void ()*)() nounwind
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; CHECK: ld [[FP:[0-9]+]], 1024(0)
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; CHECK: ld 11, 1040(0)
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; CHECK: ld 2, 1032(0)
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; CHECK-NEXT: mtctr [[FP]]
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; CHECK-NEXT: bctrl
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; CHECK-NEXT: ld 2, 40(1)
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ret void
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}
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declare double @sin(double) nounwind
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; External functions call should also have a 'nop'
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define double @test_external(double %x) nounwind {
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; CHECK-LABEL: test_external:
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%call = tail call double @sin(double %x) nounwind
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; CHECK: bl sin
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; CHECK-NEXT: nop
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ret double %call
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}
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; The 'ld 2, 40(1)' really must always come directly after the bctrl to make
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; the unwinding code in libgcc happy.
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@g = external global void ()*
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declare void @h(i64)
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define void @test_indir_toc_reload(i64 %x) {
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%1 = load void ()*, void ()** @g
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call void %1()
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call void @h(i64 %x)
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ret void
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; CHECK-LABEL: @test_indir_toc_reload
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; CHECK: bctrl
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; CHECK-NEXT: ld 2, 40(1)
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; CHECK: blr
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}
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