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Followup to 132316; accept arbitrary constants, add with a constant,

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sub with a non-constant.  Fix comments, enlarge test case.
rdar://problem/6501862


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132348 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Stuart Hastings 2011-05-31 19:29:55 +00:00
parent f729e91353
commit df48e84b5b
2 changed files with 55 additions and 15 deletions
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25
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -136,19 +136,26 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
}
}
// (1 - X) * (-2) -> (x - 1) * 2, for all positive nonzero powers of 2
// The "* 2" thus becomes a potential shifting opportunity.
// (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
// (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
// The "* (2**n)" thus becomes a potential shifting opportunity.
{
const APInt & Val = CI->getValue();
const APInt &PosVal = Val.abs();
if (Val.isNegative() && PosVal.isPowerOf2()) {
Value *X = 0;
if (match(Op0, m_Sub(m_One(), m_Value(X)))) {
// ConstantInt::get(Op0->getType(), 2);
Value *Sub = Builder->CreateSub(X, ConstantInt::get(X->getType(), 1),
"dec1");
return BinaryOperator::CreateMul(Sub, ConstantInt::get(X->getType(),
PosVal));
Value *X = 0, *Y = 0;
ConstantInt *C1 = 0;
if (Op0->hasOneUse() &&
(match(Op0, m_Sub(m_Value(Y), m_Value(X)))) ||
(match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))) {
Value *Sub;
if (C1) // Matched ADD of constant, negate both operands:
Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
else // Matched SUB, swap operands:
Sub = Builder->CreateSub(X, Y, "suba");
return
BinaryOperator::CreateMul(Sub,
ConstantInt::get(X->getType(), PosVal));
}
}
}

45
test/Transforms/InstCombine/2011-05-28-swapmulsub.ll
View File

@ -2,18 +2,14 @@
; RUN: opt -S -instcombine < %s | FileCheck %s
target triple = "x86_64-apple-macosx10.6.6"
define zeroext i16 @foo(i32 %on_off, i16* %puls) nounwind uwtable ssp {
define zeroext i16 @foo1(i32 %on_off) nounwind uwtable ssp {
entry:
%on_off.addr = alloca i32, align 4
%puls.addr = alloca i16*, align 8
%a = alloca i32, align 4
store i32 %on_off, i32* %on_off.addr, align 4
store i16* %puls, i16** %puls.addr, align 8
%tmp = load i32* %on_off.addr, align 4
; CHECK-NOT: sub
; CHECK-NOT: mul
; (1 - %tmp) * (-2) -> (%tmp - 1) * 2
%sub = sub i32 1, %tmp
; CHECK-NOT: mul i32
%mul = mul i32 %sub, -2
; CHECK: shl
; CHECK-NEXT: add
@ -22,3 +18,40 @@ entry:
%conv = trunc i32 %tmp1 to i16
ret i16 %conv
}
define zeroext i16 @foo2(i32 %on_off, i32 %q) nounwind uwtable ssp {
entry:
%on_off.addr = alloca i32, align 4
%q.addr = alloca i32, align 4
%a = alloca i32, align 4
store i32 %on_off, i32* %on_off.addr, align 4
store i32 %q, i32* %q.addr, align 4
%tmp = load i32* %q.addr, align 4
%tmp1 = load i32* %on_off.addr, align 4
%sub = sub i32 %tmp, %tmp1
; CHECK-NOT: mul i32
%mul = mul i32 %sub, -4
; CHECK: sub i32
; CHECK-NEXT: shl
store i32 %mul, i32* %a, align 4
%tmp2 = load i32* %a, align 4
%conv = trunc i32 %tmp2 to i16
ret i16 %conv
}
define zeroext i16 @foo3(i32 %on_off) nounwind uwtable ssp {
entry:
%on_off.addr = alloca i32, align 4
%a = alloca i32, align 4
store i32 %on_off, i32* %on_off.addr, align 4
%tmp = load i32* %on_off.addr, align 4
%sub = sub i32 7, %tmp
; CHECK-NOT: mul i32
%mul = mul i32 %sub, -4
; CHECK: shl
; CHECK-NEXT: add
store i32 %mul, i32* %a, align 4
%tmp1 = load i32* %a, align 4
%conv = trunc i32 %tmp1 to i16
ret i16 %conv
}