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InstCombine: allow unmasked icmps to be combined with logical ops

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"(icmp op i8 A, B)" is equivalent to "(icmp op i8 (A & 0xff), B)" as a
degenerate case. Allowing this as a "masked" comparison when analysing "(icmp)
&/| (icmp)" allows us to combine them in more cases.

rdar://problem/7625728

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189931 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2013-09-04 11:57:17 +00:00
parent 7bfabdac4e
commit 0415b1810b
2 changed files with 59 additions and 9 deletions
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38
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -568,14 +568,22 @@ static unsigned foldLogOpOfMaskedICmpsHelper(Value*& A,
L21 = L22 = L1 = 0;
} else {
// Look for ANDs in the LHS icmp.
if (match(L1, m_And(m_Value(L11), m_Value(L12)))) {
if (!match(L2, m_And(m_Value(L21), m_Value(L22))))
L21 = L22 = 0;
} else {
if (!match(L2, m_And(m_Value(L11), m_Value(L12))))
return 0;
std::swap(L1, L2);
if (!L1->getType()->isIntegerTy()) {
// You can icmp pointers, for example. They really aren't masks.
L11 = L12 = 0;
} else if (!match(L1, m_And(m_Value(L11), m_Value(L12)))) {
// Any icmp can be viewed as being trivially masked; if it allows us to
// remove one, it's worth it.
L11 = L1;
L12 = Constant::getAllOnesValue(L1->getType());
}
if (!L2->getType()->isIntegerTy()) {
// You can icmp pointers, for example. They really aren't masks.
L21 = L22 = 0;
} else if (!match(L2, m_And(m_Value(L21), m_Value(L22)))) {
L21 = L2;
L22 = Constant::getAllOnesValue(L2->getType());
}
}
@ -596,7 +604,14 @@ static unsigned foldLogOpOfMaskedICmpsHelper(Value*& A,
return 0;
}
E = R2; R1 = 0; ok = true;
} else if (match(R1, m_And(m_Value(R11), m_Value(R12)))) {
} else if (R1->getType()->isIntegerTy()) {
if (!match(R1, m_And(m_Value(R11), m_Value(R12)))) {
// As before, model no mask as a trivial mask if it'll let us do an
// optimisation.
R11 = R1;
R12 = Constant::getAllOnesValue(R1->getType());
}
if (R11 == L11 || R11 == L12 || R11 == L21 || R11 == L22) {
A = R11; D = R12; E = R2; ok = true;
} else if (R12 == L11 || R12 == L12 || R12 == L21 || R12 == L22) {
@ -609,7 +624,12 @@ static unsigned foldLogOpOfMaskedICmpsHelper(Value*& A,
return 0;
// Look for ANDs in on the right side of the RHS icmp.
if (!ok && match(R2, m_And(m_Value(R11), m_Value(R12)))) {
if (!ok && R2->getType()->isIntegerTy()) {
if (!match(R2, m_And(m_Value(R11), m_Value(R12)))) {
R11 = R2;
R12 = Constant::getAllOnesValue(R2->getType());
}
if (R11 == L11 || R11 == L12 || R11 == L21 || R11 == L22) {
A = R11; D = R12; E = R1; ok = true;
} else if (R12 == L11 || R12 == L12 || R12 == L21 || R12 == L22) {

30
test/Transforms/InstCombine/icmp-logical.ll
View File

@ -120,3 +120,33 @@ define i1 @masked_or_allzeroes_notoptimised(i32 %A) {
ret i1 %res
}
define i1 @nomask_lhs(i32 %in) {
; CHECK-LABEL: @nomask_lhs
; CHECK: [[MASK:%.*]] = and i32 %in, 1
; CHECK: icmp eq i32 [[MASK]], 0
; CHECK-NOT: icmp
; CHECK: ret i1
%tst1 = icmp eq i32 %in, 0
%masked = and i32 %in, 1
%tst2 = icmp eq i32 %masked, 0
%val = or i1 %tst1, %tst2
ret i1 %val
}
define i1 @nomask_rhs(i32 %in) {
; CHECK-LABEL: @nomask_rhs
; CHECK: [[MASK:%.*]] = and i32 %in, 1
; CHECK: icmp eq i32 [[MASK]], 0
; CHECK-NOT: icmp
; CHECK: ret i1
%masked = and i32 %in, 1
%tst1 = icmp eq i32 %masked, 0
%tst2 = icmp eq i32 %in, 0
%val = or i1 %tst1, %tst2
ret i1 %val
}