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ARM: Fix incorrect pack pattern for thumb2

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Propagate the fix from r185712 to Thumb2 codegen as well. Original
commit message applies here as well:

A "pkhtb x, x, y asr #num" uses the lower 16 bits of "y asr #num" and
packs them in the bottom half of "x". An arithmetic and logic shift are
only equivalent in this context if the shift amount is 16. We would be
shifting in ones into the bottom 16bits instead of zeros if "y" is
negative.

rdar://14338767

llvm-svn: 185982
This commit is contained in:
Jim Grosbach 2013-07-09 22:59:22 +00:00
parent 16d8086f72
commit d6be90a2b8
2 changed files with 30 additions and 2 deletions
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7
lib/Target/ARM/ARMInstrThumb2.td
View File

@ -2951,7 +2951,12 @@ def t2PKHTB : T2ThreeReg<
// Alternate cases for PKHTB where identities eliminate some nodes. Note that
// a shift amount of 0 is *not legal* here, it is PKHBT instead.
def : T2Pat<(or (and rGPR:$src1, 0xFFFF0000), (srl rGPR:$src2, imm16_31:$sh)),
// We also can not replace a srl (17..31) by an arithmetic shift we would use in
// pkhtb src1, src2, asr (17..31).
def : T2Pat<(or (and rGPR:$src1, 0xFFFF0000), (srl rGPR:$src2, imm16:$sh)),
(t2PKHTB rGPR:$src1, rGPR:$src2, imm16:$sh)>,
Requires<[HasT2ExtractPack, IsThumb2]>;
def : T2Pat<(or (and rGPR:$src1, 0xFFFF0000), (sra rGPR:$src2, imm16_31:$sh)),
(t2PKHTB rGPR:$src1, rGPR:$src2, imm16_31:$sh)>,
Requires<[HasT2ExtractPack, IsThumb2]>;
def : T2Pat<(or (and rGPR:$src1, 0xFFFF0000),

25
test/CodeGen/Thumb2/thumb2-pack.ll
View File

@ -88,10 +88,33 @@ define i32 @test7(i32 %X, i32 %Y) {
}
; CHECK: test8
; CHECK: pkhtb r0, r0, r1, asr #22
; CHECK-NOT: pkhtb r0, r0, r1, asr #22
; pkhtb does an arithmetic shift, not a logical shift. Make sure we don't
; use it for problematic cases when whether sign bits would be shifted in
; would matter.
define i32 @test8(i32 %X, i32 %Y) {
%tmp1 = and i32 %X, -65536
%tmp3 = lshr i32 %Y, 22
%tmp57 = or i32 %tmp3, %tmp1
ret i32 %tmp57
}
; CHECK: test9:
; CHECK: pkhtb r0, r0, r1, asr #16
define i32 @test9(i32 %src1, i32 %src2) {
entry:
%tmp = and i32 %src1, -65536
%tmp2 = lshr i32 %src2, 16
%tmp3 = or i32 %tmp, %tmp2
ret i32 %tmp3
}
; CHECK: test10
; CHECK: pkhtb r0, r0, r1, asr #22
define i32 @test10(i32 %X, i32 %Y) {
%tmp1 = and i32 %X, -65536
%tmp3 = ashr i32 %Y, 22
%tmp57 = or i32 %tmp3, %tmp1
ret i32 %tmp57
}