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[PowerPC] Use subfic instruction for subtract from immediate

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Provide a 64-bit pattern to use SUBFIC for subtracting from a 16-bit immediate.
The corresponding pattern already exists for 32-bit integers.

Committing on behalf of Hiroshi Inoue.

Differential Revision: https://reviews.llvm.org/D29387

llvm-svn: 296144
This commit is contained in:
Nemanja Ivanovic 2017-02-24 18:16:06 +00:00
parent 6a343cafa0
commit f87f345963
2 changed files with 45 additions and 0 deletions
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4
lib/Target/PowerPC/PPCInstr64Bit.td
View File

@ -1232,6 +1232,10 @@ def : Pat<(srl i64:$rS, i32:$rB),
def : Pat<(shl i64:$rS, i32:$rB),
(SLD $rS, $rB)>;
// SUBFIC
def : Pat<(sub imm64SExt16:$imm, i64:$in),
(SUBFIC8 $in, imm:$imm)>;
// SHL/SRL
def : Pat<(shl i64:$in, (i32 imm:$imm)),
(RLDICR $in, imm:$imm, (SHL64 imm:$imm))>;

41
test/CodeGen/PowerPC/subtract_from_imm.ll Normal file
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@ -0,0 +1,41 @@
; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
; RUN: llc -verify-machineinstrs -mtriple=powerpc64-unknown-linux-gnu < %s | FileCheck %s
; Make sure that the subfic is generated iff possible
define i64 @subtract_from_imm1(i64 %v) nounwind readnone {
entry:
; CHECK-LABEL: subtract_from_imm1
; CHECK: subfic 3, 3, 32767
; CHECK: blr
%sub = sub i64 32767, %v
ret i64 %sub
}
define i64 @subtract_from_imm2(i64 %v) nounwind readnone {
entry:
; CHECK-LABEL: subtract_from_imm2
; CHECK-NOT: subfic
; CHECK: blr
%sub = sub i64 32768, %v
ret i64 %sub
}
define i64 @subtract_from_imm3(i64 %v) nounwind readnone {
entry:
; CHECK-LABEL: subtract_from_imm3
; CHECK: subfic 3, 3, -32768
; CHECK: blr
%sub = sub i64 -32768, %v
ret i64 %sub
}
define i64 @subtract_from_imm4(i64 %v) nounwind readnone {
entry:
; CHECK-LABEL: subtract_from_imm4
; CHECK-NOT: subfic
; CHECK: blr
%sub = sub i64 -32769, %v
ret i64 %sub
}