38 lines
1.7 KiB
LLVM
38 lines
1.7 KiB
LLVM
; RUN: llc < %s -relocation-model=pic -O2 -disable-fp-elim -o - | FileCheck %s
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; RUN: llc < %s -relocation-model=pic -O2 -o - | FileCheck %s
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; This test runs twice with different options regarding the frame pointer:
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; first the elimination is disabled, then it is enabled. The disabled case is
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; the "control group".
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; The function 'foo' below is marked with the "no-frame-pointer-elim-non-leaf"
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; attribute which dictates that the frame pointer should not be eliminated
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; unless the function is a leaf (i.e. it doesn't call any other function).
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; Now, 'foo' is not a leaf function, because it performs a TLS access which on
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; X86 ELF in PIC mode is expanded as a library call.
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; This call is represented with a pseudo-instruction which doesn't appear to be
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; a call when inspected by the analysis passes (it doesn't have the "isCall"
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; flag), and the ISel lowering code creating the pseudo was not informing the
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; MachineFrameInfo that the function contained calls. This affected the decision
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; whether to eliminate the frame pointer.
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; With the fix, the "hasCalls" flag is set in the MFI for the function whenever
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; a TLS access pseudo-instruction is created, so 'foo' appears to be a non-leaf
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; function, and the difference in the options does not affect codegen: both
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; versions will have a frame pointer.
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; Test that there's some frame pointer usage in 'foo'...
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; CHECK: foo:
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; CHECK: pushq %rbp
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; CHECK: movq %rsp, %rbp
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; ... and the TLS library call is also present.
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; CHECK: leaq x@TLSGD(%rip), %rdi
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; CHECK: callq __tls_get_addr@PLT
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@x = thread_local global i32 0
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define i32 @foo() "no-frame-pointer-elim-non-leaf" {
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%a = load i32, i32* @x, align 4
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ret i32 %a
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}
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