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[FastISel][AArch64] Emit immediate version of icmp (subs) for null pointer check.

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This is a minor change to use the immediate version when the operand is a null
value. This should get rid of an unnecessary 'mov' instruction in debug
builds and align the code more with the one generated by SelectionDAG.

This fixes rdar://problem/18785125.

llvm-svn: 220713
This commit is contained in:
Juergen Ributzka 2014-10-27 19:58:36 +00:00
parent 76c57b0570
commit b3117b0b86
2 changed files with 26 additions and 2 deletions
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8
lib/Target/AArch64/AArch64FastISel.cpp
View File

@ -1084,7 +1084,7 @@ unsigned AArch64FastISel::emitAddSub(bool UseAdd, MVT RetVT, const Value *LHS,
RetVT.SimpleTy = std::max(RetVT.SimpleTy, MVT::i32);
// Canonicalize immediates to the RHS first.
if (UseAdd && isa<ConstantInt>(LHS) && !isa<ConstantInt>(RHS))
if (UseAdd && isa<Constant>(LHS) && !isa<Constant>(RHS))
std::swap(LHS, RHS);
// Canonicalize mul by power of 2 to the RHS.
@ -1118,7 +1118,11 @@ unsigned AArch64FastISel::emitAddSub(bool UseAdd, MVT RetVT, const Value *LHS,
else
ResultReg = emitAddSub_ri(UseAdd, RetVT, LHSReg, LHSIsKill, Imm, SetFlags,
WantResult);
}
} else if (const auto *C = dyn_cast<Constant>(RHS))
if (C->isNullValue())
ResultReg = emitAddSub_ri(UseAdd, RetVT, LHSReg, LHSIsKill, 0, SetFlags,
WantResult);
if (ResultReg)
return ResultReg;

20
test/CodeGen/AArch64/arm64-fast-isel-icmp.ll
View File

@ -40,6 +40,26 @@ entry:
ret i32 %conv
}
define i32 @icmp_eq_ptr(i8* %a) {
entry:
; CHECK-LABEL: icmp_eq_ptr
; CHECK: cmp x0, #0
; CHECK-NEXT: cset {{.+}}, eq
%cmp = icmp eq i8* %a, null
%conv = zext i1 %cmp to i32
ret i32 %conv
}
define i32 @icmp_ne_ptr(i8* %a) {
entry:
; CHECK-LABEL: icmp_ne_ptr
; CHECK: cmp x0, #0
; CHECK-NEXT: cset {{.+}}, ne
%cmp = icmp ne i8* %a, null
%conv = zext i1 %cmp to i32
ret i32 %conv
}
define i32 @icmp_ugt(i32 %a, i32 %b) nounwind ssp {
entry:
; CHECK-LABEL: icmp_ugt