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Implement a pretty general logical shift propagation

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framework, which is good at ripping through bitfield
operations.  This generalize a bunch of the existing
xforms that instcombine does, such as 
  (x << c) >> c -> and
to handle intermediate logical nodes.  This is useful for
ripping up the "promote to large integer" code produced by
SRoA.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112304 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2010-08-27 22:24:38 +00:00
parent dbb350a5c7
commit 29cc0b3660
3 changed files with 244 additions and 6 deletions
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21
test/Transforms/InstCombine/shift.ll
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@@ -130,8 +130,8 @@ define i8 @test13(i8 %A) {
;; D = ((B | 1234) << 4) === ((B << 4)|(1234 << 4)
define i32 @test14(i32 %A) {
; CHECK: @test14
; CHECK-NEXT: or i32 %A, 19744
; CHECK-NEXT: and i32
; CHECK-NEXT: %B = and i32 %A, -19760
; CHECK-NEXT: or i32 %B, 19744
; CHECK-NEXT: ret i32
%B = lshr i32 %A, 4 ; <i32> [#uses=1]
%C = or i32 %B, 1234 ; <i32> [#uses=1]
@@ -350,8 +350,8 @@ entry:
%tmp10 = lshr i32 %tmp917, 31
ret i32 %tmp10
; CHECK: @test29
; CHECK: %tmp101 = lshr i64 %d18, 63
; CHECK: %tmp10 = trunc i64 %tmp101 to i32
; CHECK: %tmp916 = lshr i64 %d18, 63
; CHECK: %tmp10 = trunc i64 %tmp916 to i32
}
@@ -412,3 +412,16 @@ define i1 @test35(i32 %X) {
; CHECK: ret i1 %tmp2
}
define i128 @test36(i128 %A, i128 %B) {
entry:
%tmp27 = shl i128 %A, 64
%tmp23 = shl i128 %B, 64
%ins = or i128 %tmp23, %tmp27
%tmp45 = lshr i128 %ins, 64
ret i128 %tmp45
; CHECK: %tmp231 = or i128 %B, %A
; CHECK: %ins = and i128 %tmp231, 18446744073709551615
; CHECK: ret i128 %ins
}