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Smarter isel of ldrsb / ldrsh. Only make use of these when [r,r] address is feasible.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75360 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2009-07-11 07:08:13 +00:00
parent 446c428bf3
commit 2f297df02e
4 changed files with 27 additions and 24 deletions
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15
lib/Target/ARM/ARMISelDAGToDAG.cpp
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@ -454,16 +454,11 @@ bool ARMDAGToDAGISel::SelectThumbAddrModeRR(SDValue Op, SDValue N,
// FIXME dl should come from the parent load or store, not the address
DebugLoc dl = Op.getDebugLoc();
if (N.getOpcode() != ISD::ADD) {
Base = N;
// We must materialize a zero in a reg! Returning a constant here
// wouldn't work without additional code to position the node within
// ISel's topological ordering in a place where ISel will process it
// normally. Instead, just explicitly issue a tMOVri8 node!
SDValue CC = CurDAG->getRegister(ARM::CPSR, MVT::i32);
SDValue Pred = CurDAG->getTargetConstant(0xEULL, MVT::i32);
SDValue PredReg = CurDAG->getRegister(0, MVT::i32);
SDValue Ops[] = { CC, CurDAG->getTargetConstant(0, MVT::i32), Pred, PredReg };
Offset = SDValue(CurDAG->getTargetNode(ARM::tMOVi8, dl, MVT::i32, Ops,4),0);
ConstantSDNode *NC = dyn_cast<ConstantSDNode>(N);
if (!NC || NC->getZExtValue() != 0)
return false;
Base = Offset = N;
return true;
}

10
lib/Target/ARM/ARMInstrThumb.td
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@ -224,10 +224,12 @@ def tLDRH : T1pI2<(outs tGPR:$dst), (ins t_addrmode_s2:$addr),
"ldrh", " $dst, $addr",
[(set tGPR:$dst, (zextloadi16 t_addrmode_s2:$addr))]>;
let AddedComplexity = 10 in
def tLDRSB : T1pI1<(outs tGPR:$dst), (ins t_addrmode_rr:$addr),
"ldrsb", " $dst, $addr",
[(set tGPR:$dst, (sextloadi8 t_addrmode_rr:$addr))]>;
let AddedComplexity = 10 in
def tLDRSH : T1pI2<(outs tGPR:$dst), (ins t_addrmode_rr:$addr),
"ldrsh", " $dst, $addr",
[(set tGPR:$dst, (sextloadi16 t_addrmode_rr:$addr))]>;
@ -620,6 +622,14 @@ def : T1Pat<(extloadi1 t_addrmode_s1:$addr), (tLDRB t_addrmode_s1:$addr)>;
def : T1Pat<(extloadi8 t_addrmode_s1:$addr), (tLDRB t_addrmode_s1:$addr)>;
def : T1Pat<(extloadi16 t_addrmode_s2:$addr), (tLDRH t_addrmode_s2:$addr)>;
// If it's possible to use [r,r] address mode for sextload, select to
// ldr{b|h} + sxt{b|h} instead.
def : TPat<(sextloadi8 t_addrmode_s1:$addr),
(tSXTB (tLDRB t_addrmode_s1:$addr))>;
def : TPat<(sextloadi16 t_addrmode_s2:$addr),
(tSXTH (tLDRH t_addrmode_s2:$addr))>;
// Large immediate handling.
// Two piece imms.

9
lib/Target/ARM/README-Thumb.txt
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@ -244,12 +244,3 @@ to toggle the 's' bit since they do not set CPSR when they are inside IT blocks.
Make use of hi register variants of cmp: tCMPhir / tCMPZhir.
//===---------------------------------------------------------------------===//
Rather than generating ldrsb, sometimes it's better to select to ldrb + sxtb.
The problem is ldrsb addressing mode [r, r] means the zero offset requires an
extra move. e.g. ldr_ext.ll test3:
movs r1, #0
ldrsb r0, [r0, r1]
=>
ldrb r0, [r0, #0]
sxtb r0, r0

15
test/CodeGen/Thumb/ldr_ext.ll
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@ -1,27 +1,34 @@
; RUN: llvm-as < %s | llc -march=thumb | grep ldrb | count 1
; RUN: llvm-as < %s | llc -march=thumb | grep ldrh | count 1
; RUN: llvm-as < %s | llc -march=thumb | grep ldrsb | count 1
; RUN: llvm-as < %s | llc -march=thumb | grep ldrsh | count 1
; RUN: llvm-as < %s | llc -march=thumb | FileCheck %s
define i32 @test1(i8* %v.pntr.s0.u1) {
; CHECK: test1:
; CHECK: ldrb
%tmp.u = load i8* %v.pntr.s0.u1
%tmp1.s = zext i8 %tmp.u to i32
ret i32 %tmp1.s
}
define i32 @test2(i16* %v.pntr.s0.u1) {
; CHECK: test2:
; CHECK: ldrh
%tmp.u = load i16* %v.pntr.s0.u1
%tmp1.s = zext i16 %tmp.u to i32
ret i32 %tmp1.s
}
define i32 @test3(i8* %v.pntr.s1.u0) {
; CHECK: test3:
; CHECK: ldrb
; CHECK: sxtb
%tmp.s = load i8* %v.pntr.s1.u0
%tmp1.s = sext i8 %tmp.s to i32
ret i32 %tmp1.s
}
define i32 @test4() {
; CHECK: test4:
; CHECK: movs
; CHECK: ldrsh
%tmp.s = load i16* null
%tmp1.s = sext i16 %tmp.s to i32
ret i32 %tmp1.s