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[PowerPC] Implement BuildSDIVPow2, lower i64 pow2 sdiv using sradi

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PPCISelDAGToDAG contained existing code to lower i32 sdiv by a power-of-2 using
srawi/addze, but did not implement the i64 case. DAGCombine now contains a
callback specifically designed for this purpose (BuildSDIVPow2), and part of
the logic has been moved to an implementation of that callback. Doing this
lowering using BuildSDIVPow2 likely does not matter, compared to handling
everything in PPCISelDAGToDAG, for the positive divisor case, but the negative
divisor case, which generates an additional negation, can potentially benefit
from additional folding from DAGCombine. Now, both the i32 and the i64 cases
have been implemented.

Fixes PR20732.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224033 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel
2014-12-11 18:37:52 +00:00
parent de15d01f9d
commit 31f6bdbbbe
4 changed files with 116 additions and 30 deletions
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58
test/CodeGen/PowerPC/sdiv-pow2.ll Normal file
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@@ -0,0 +1,58 @@
; RUN: llc -mcpu=ppc64 < %s | FileCheck %s
target datalayout = "E-m:e-i64:64-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
; Function Attrs: nounwind readnone
define signext i32 @foo4(i32 signext %a) #0 {
entry:
%div = sdiv i32 %a, 8
ret i32 %div
; CHECK-LABEL @foo4
; CHECK: srawi [[REG1:[0-9]+]], 3, 3
; CHECK: addze [[REG2:[0-9]+]], [[REG1]]
; CHECK: extsw 3, [[REG2]]
; CHECK: blr
}
; Function Attrs: nounwind readnone
define i64 @foo8(i64 %a) #0 {
entry:
%div = sdiv i64 %a, 8
ret i64 %div
; CHECK-LABEL @foo8
; CHECK: sradi [[REG1:[0-9]+]], 3, 3
; CHECK: addze 3, [[REG1]]
; CHECK: blr
}
; Function Attrs: nounwind readnone
define signext i32 @foo4n(i32 signext %a) #0 {
entry:
%div = sdiv i32 %a, -8
ret i32 %div
; CHECK-LABEL: @foo4n
; CHECK: srawi [[REG1:[0-9]+]], 3, 3
; CHECK: addze [[REG2:[0-9]+]], [[REG1]]
; CHECK: neg [[REG3:[0-9]+]], [[REG2]]
; CHECK: extsw 3, [[REG3]]
; CHECK: blr
}
; Function Attrs: nounwind readnone
define i64 @foo8n(i64 %a) #0 {
entry:
%div = sdiv i64 %a, -8
ret i64 %div
; CHECK-LABEL: @foo8n
; CHECK: sradi [[REG1:[0-9]+]], 3, 3
; CHECK: addze [[REG2:[0-9]+]], [[REG1]]
; CHECK: neg 3, [[REG2]]
; CHECK: blr
}
attributes #0 = { nounwind readnone }