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[AArch64, ARM] Enable GlobalMerge with -O3 rather than -O1.

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The pass used to be enabled by default with CodeGenOpt::Less (-O1).
This is too aggressive, considering the pass indiscriminately merges
all globals together.

Currently, performance doesn't always improve, and, on code that uses
few globals (e.g., the odd file- or function- static), more often than
not is degraded by the optimization.  Lengthy discussion can be found
on llvmdev (AArch64-focused;  ARM has similar problems):
  http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-February/082800.html
Also, it makes tooling and debuggers less useful when dealing with
globals and data sections.

GlobalMerge needs to better identify those cases that benefit, and this
will be done separately.  In the meantime, move the pass to run with
-O3 rather than -O1, on both ARM and AArch64.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233024 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ahmed Bougacha
2015-03-23 21:17:36 +00:00
parent 6a4686f3f1
commit c9ad3ab624
13 changed files with 27 additions and 26 deletions
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9
test/CodeGen/ARM/global-merge-1.ll
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@@ -1,9 +1,10 @@
; RUN: llc %s -O0 -o - | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O0 -o - -enable-global-merge=false | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O0 -o - -enable-global-merge=true | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O1 -o - | FileCheck -check-prefix=MERGE %s
; RUN: llc %s -O1 -o - | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O1 -o - -enable-global-merge=false | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O1 -o - -enable-global-merge=true | FileCheck -check-prefix=MERGE %s
; RUN: llc %s -O1 -o - -enable-global-merge=true | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O3 -o - | FileCheck -check-prefix=MERGE %s
; RUN: llc %s -O3 -o - -enable-global-merge=false | FileCheck -check-prefix=NO-MERGE %s
; RUN: llc %s -O3 -o - -enable-global-merge=true | FileCheck -check-prefix=MERGE %s
; MERGE-NOT: .zerofill __DATA,__bss,_bar,20,2
; MERGE-NOT: .zerofill __DATA,__bss,_baz,20,2