[PATCH] D24237: [ARM] Promote small global constants to constant pools

[James Molloy via llvm-commits]

jmolloy created this revision.
jmolloy added reviewers: olista01, t.p.northover, mcrosier.
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If a constant is unamed_addr and is only used within one function, we can save
on the code size and runtime cost of an indirection by changing the global's storage
to inside the constant pool. For example, instead of:

      ldr r0, .CPI0
      bl printf
      bx lr
    .CPI0: &format_string
    format_string: .asciz "hello, world!\n"

We can emit:

      adr r0, .CPI0
      bl printf
      bx lr
    .CPI0: .asciz "hello, world!\n"

This can cause significant code size savings when many small strings are used in one
function (4 bytes per string).

Repository:
  rL LLVM

https://reviews.llvm.org/D24237

Files:
  lib/Target/ARM/ARMAsmPrinter.cpp
  lib/Target/ARM/ARMAsmPrinter.h
  lib/Target/ARM/ARMISelLowering.cpp
  lib/Target/ARM/ARMMachineFunctionInfo.h
  test/CodeGen/ARM/constantpool-promote.ll

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