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reuse negates where possible instead of always creating them from scratch.

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This allows us to optimize test12 into:

define i32 @test12(i32 %X) {
  %factor = mul i32 %X, -3                        ; <i32> [#uses=1]
  %Z = add i32 %factor, 6                         ; <i32> [#uses=1]
  ret i32 %Z
}

instead of:

define i32 @test12(i32 %X) {
  %Y = sub i32 6, %X                              ; <i32> [#uses=1]
  %C = sub i32 %Y, %X                             ; <i32> [#uses=1]
  %Z = sub i32 %C, %X                             ; <i32> [#uses=1]
  ret i32 %Z
}



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92373 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-12-31 20:34:32 +00:00
parent f31e2e92a8
commit 3523993451
2 changed files with 43 additions and 1 deletions
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13
test/Transforms/Reassociate/basictest.ll
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@@ -165,4 +165,17 @@ define i32 @test11(i32 %W) {
; CHECK-NEXT: ret i32
}
define i32 @test12(i32 %X) {
%A = sub i32 1, %X
%B = sub i32 2, %X
%C = sub i32 3, %X
%Y = add i32 %A ,%B
%Z = add i32 %Y, %C
ret i32 %Z
; CHECK: @test12
; CHECK-NEXT: mul i32 %X, -3
; CHECK-NEXT: add i32{{.*}}, 6
; CHECK-NEXT: ret i32
}