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ARM: tell LLVM about zext properties of ldrexb/ldrexh

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Implementing this via ComputeMaskedBits has two advantages:
  + It actually works. DAGISel doesn't deal with the chains properly
    in the previous pattern-based solution, so they never trigger.
  + The information can be used in other DAG combines, as well as the
    trivial "get rid of truncs". For example if the trunc is in a
    different basic block.

rdar://problem/16227836

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205540 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2014-04-03 15:10:35 +00:00
parent 769a6f2116
commit d5561bb1f0
5 changed files with 56 additions and 28 deletions
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14
lib/Target/ARM/ARMISelLowering.cpp
View File

@ -9964,6 +9964,20 @@ void ARMTargetLowering::computeMaskedBitsForTargetNode(const SDValue Op,
KnownOne &= KnownOneRHS;
return;
}
case ISD::INTRINSIC_W_CHAIN: {
ConstantSDNode *CN = cast<ConstantSDNode>(Op->getOperand(1));
Intrinsic::ID IntID = static_cast<Intrinsic::ID>(CN->getZExtValue());
switch (IntID) {
default: return;
case Intrinsic::arm_ldaex:
case Intrinsic::arm_ldrex: {
EVT VT = cast<MemIntrinsicSDNode>(Op)->getMemoryVT();
unsigned MemBits = VT.getScalarType().getSizeInBits();
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
return;
}
}
}
}
}

8
lib/Target/ARM/ARMInstrInfo.td
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@ -4476,19 +4476,11 @@ def CLREX : AXI<(outs), (ins), MiscFrm, NoItinerary, "clrex",
let Inst{31-0} = 0b11110101011111111111000000011111;
}
def : ARMPat<(and (ldrex_1 addr_offset_none:$addr), 0xff),
(LDREXB addr_offset_none:$addr)>;
def : ARMPat<(and (ldrex_2 addr_offset_none:$addr), 0xffff),
(LDREXH addr_offset_none:$addr)>;
def : ARMPat<(strex_1 (and GPR:$Rt, 0xff), addr_offset_none:$addr),
(STREXB GPR:$Rt, addr_offset_none:$addr)>;
def : ARMPat<(strex_2 (and GPR:$Rt, 0xffff), addr_offset_none:$addr),
(STREXH GPR:$Rt, addr_offset_none:$addr)>;
def : ARMPat<(and (ldaex_1 addr_offset_none:$addr), 0xff),
(LDAEXB addr_offset_none:$addr)>;
def : ARMPat<(and (ldaex_2 addr_offset_none:$addr), 0xffff),
(LDAEXH addr_offset_none:$addr)>;
def : ARMPat<(stlex_1 (and GPR:$Rt, 0xff), addr_offset_none:$addr),
(STLEXB GPR:$Rt, addr_offset_none:$addr)>;
def : ARMPat<(stlex_2 (and GPR:$Rt, 0xffff), addr_offset_none:$addr),

22
test/CodeGen/ARM/atomic-ops-v8.ll
View File

@ -805,8 +805,8 @@ define i8 @test_atomic_load_umin_i8(i8 zeroext %offset) nounwind {
; CHECK: ldrexb r[[OLD:[0-9]+]], {{.*}}[[ADDR]]
; r0 below is a reasonable guess but could change: it certainly comes into the
; function there.
; CHECK-NEXT: uxtb r[[OLDX]], r[[OLD]]
; CHECK-NEXT: cmp r[[OLDX]], r0
; CHECK-NEXT: mov r[[NEW:[0-9]+]], r0
; CHECK-NEXT: cmp r[[OLD]], r0
; Thumb mode: it ls
; CHECK: movls r[[NEW]], r[[OLD]]
; CHECK-NEXT: strexb [[STATUS:r[0-9]+]], r[[NEW]], {{.*}}[[ADDR]]
@ -831,8 +831,8 @@ define i16 @test_atomic_load_umin_i16(i16 zeroext %offset) nounwind {
; CHECK: ldaexh r[[OLD:[0-9]+]], {{.*}}[[ADDR]]
; r0 below is a reasonable guess but could change: it certainly comes into the
; function there.
; CHECK-NEXT: uxth r[[OLDX]], r[[OLD]]
; CHECK-NEXT: cmp r[[OLDX]], r0
; CHECK-NEXT: mov r[[NEW:[0-9]+]], r0
; CHECK-NEXT: cmp r[[OLD]], r0
; Thumb mode: it ls
; CHECK: movls r[[NEW]], r[[OLD]]
; CHECK-NEXT: strexh [[STATUS:r[0-9]+]], r[[NEW]], {{.*}}[[ADDR]]
@ -919,8 +919,8 @@ define i8 @test_atomic_load_umax_i8(i8 zeroext %offset) nounwind {
; CHECK: ldaexb r[[OLD:[0-9]+]], {{.*}}[[ADDR]]
; r0 below is a reasonable guess but could change: it certainly comes into the
; function there.
; CHECK-NEXT: uxtb r[[OLDX:[0-9]+]], r[[OLD]]
; CHECK-NEXT: cmp r[[OLDX]], r0
; CHECK-NEXT: mov r[[NEW:[0-9]+]], r0
; CHECK-NEXT: cmp r[[OLD]], r0
; Thumb mode: it hi
; CHECK: movhi r[[NEW]], r[[OLD]]
; CHECK-NEXT: stlexb [[STATUS:r[0-9]+]], r[[NEW]], {{.*}}[[ADDR]]
@ -945,8 +945,8 @@ define i16 @test_atomic_load_umax_i16(i16 zeroext %offset) nounwind {
; CHECK: ldrexh r[[OLD:[0-9]+]], {{.*}}[[ADDR]]
; r0 below is a reasonable guess but could change: it certainly comes into the
; function there.
; CHECK-NEXT: uxth r[[OLDX:[0-9]+]], r[[OLD]]
; CHECK-NEXT: cmp r[[OLDX]], r0
; CHECK-NEXT: mov r[[NEW:[0-9]+]], r0
; CHECK-NEXT: cmp r[[OLD]], r0
; Thumb mode: it hi
; CHECK: movhi r[[NEW]], r[[OLD]]
; CHECK-NEXT: strexh [[STATUS:r[0-9]+]], r[[NEW]], {{.*}}[[ADDR]]
@ -1033,8 +1033,7 @@ define i8 @test_atomic_cmpxchg_i8(i8 zeroext %wanted, i8 zeroext %new) nounwind
; CHECK: ldaexb r[[OLD:[0-9]+]], [r[[ADDR]]]
; r0 below is a reasonable guess but could change: it certainly comes into the
; function there.
; CHECK-NEXT: uxtb r[[OLDX:[0-9]+]], r[[OLD]]
; CHECK-NEXT: cmp r[[OLDX]], r0
; CHECK-NEXT: cmp r[[OLD]], r0
; CHECK-NEXT: bne .LBB{{[0-9]+}}_3
; CHECK-NEXT: BB#2:
; As above, r1 is a reasonable guess.
@ -1060,8 +1059,7 @@ define i16 @test_atomic_cmpxchg_i16(i16 zeroext %wanted, i16 zeroext %new) nounw
; CHECK: ldaexh r[[OLD:[0-9]+]], [r[[ADDR]]]
; r0 below is a reasonable guess but could change: it certainly comes into the
; function there.
; CHECK-NEXT: uxth r[[OLDX:[0-9]+]], r[[OLD]]
; CHECK-NEXT: cmp r[[OLDX]], r0
; CHECK-NEXT: cmp r[[OLD]], r0
; CHECK-NEXT: bne .LBB{{[0-9]+}}_3
; CHECK-NEXT: BB#2:
; As above, r1 is a reasonable guess.

12
test/CodeGen/ARM/ldaex-stlex.ll
View File

@ -34,17 +34,21 @@ declare i32 @llvm.arm.stlexd(i32, i32, i8*) nounwind
; CHECK-LABEL: test_load_i8:
; CHECK: ldaexb r0, [r0]
; CHECK-NOT: uxtb
define i32 @test_load_i8(i8* %addr) {
; CHECK-NOT: and
define zeroext i8 @test_load_i8(i8* %addr) {
%val = call i32 @llvm.arm.ldaex.p0i8(i8* %addr)
ret i32 %val
%val8 = trunc i32 %val to i8
ret i8 %val8
}
; CHECK-LABEL: test_load_i16:
; CHECK: ldaexh r0, [r0]
; CHECK-NOT: uxth
define i32 @test_load_i16(i16* %addr) {
; CHECK-NOT: and
define zeroext i16 @test_load_i16(i16* %addr) {
%val = call i32 @llvm.arm.ldaex.p0i16(i16* %addr)
ret i32 %val
%val16 = trunc i32 %val to i16
ret i16 %val16
}
; CHECK-LABEL: test_load_i32:

28
test/CodeGen/ARM/ldstrex.ll
View File

@ -36,17 +36,21 @@ declare i32 @llvm.arm.strexd(i32, i32, i8*) nounwind
; CHECK-LABEL: test_load_i8:
; CHECK: ldrexb r0, [r0]
; CHECK-NOT: uxtb
define i32 @test_load_i8(i8* %addr) {
; CHECK-NOT: and
define zeroext i8 @test_load_i8(i8* %addr) {
%val = call i32 @llvm.arm.ldrex.p0i8(i8* %addr)
ret i32 %val
%val8 = trunc i32 %val to i8
ret i8 %val8
}
; CHECK-LABEL: test_load_i16:
; CHECK: ldrexh r0, [r0]
; CHECK-NOT: uxth
define i32 @test_load_i16(i16* %addr) {
; CHECK-NOT: and
define zeroext i16 @test_load_i16(i16* %addr) {
%val = call i32 @llvm.arm.ldrex.p0i16(i16* %addr)
ret i32 %val
%val16 = trunc i32 %val to i16
ret i16 %val16
}
; CHECK-LABEL: test_load_i32:
@ -137,3 +141,19 @@ define void @excl_addrmode() {
ret void
}
; LLVM should know, even across basic blocks, that ldrex is setting the high
; bits of its i32 to 0. There should be no zero-extend operation.
define zeroext i8 @test_cross_block_zext_i8(i1 %tst, i8* %addr) {
; CHECK: test_cross_block_zext_i8:
; CHECK-NOT: uxtb
; CHECK-NOT: and
; CHECK: bx lr
%val = call i32 @llvm.arm.ldrex.p0i8(i8* %addr)
br i1 %tst, label %end, label %mid
mid:
ret i8 42
end:
%val8 = trunc i32 %val to i8
ret i8 %val8
}