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Followup to 132316; accept arbitrary constants, add with a constant,
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
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@ -136,19 +136,26 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
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}
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}
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// (1 - X) * (-2) -> (x - 1) * 2, for all positive nonzero powers of 2
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// The "* 2" thus becomes a potential shifting opportunity.
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// (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
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// (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
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// The "* (2**n)" thus becomes a potential shifting opportunity.
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{
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const APInt & Val = CI->getValue();
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const APInt &PosVal = Val.abs();
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if (Val.isNegative() && PosVal.isPowerOf2()) {
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Value *X = 0;
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if (match(Op0, m_Sub(m_One(), m_Value(X)))) {
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// ConstantInt::get(Op0->getType(), 2);
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Value *Sub = Builder->CreateSub(X, ConstantInt::get(X->getType(), 1),
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"dec1");
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return BinaryOperator::CreateMul(Sub, ConstantInt::get(X->getType(),
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PosVal));
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Value *X = 0, *Y = 0;
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ConstantInt *C1 = 0;
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if (Op0->hasOneUse() &&
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(match(Op0, m_Sub(m_Value(Y), m_Value(X)))) ||
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(match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))) {
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Value *Sub;
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if (C1) // Matched ADD of constant, negate both operands:
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Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
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else // Matched SUB, swap operands:
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Sub = Builder->CreateSub(X, Y, "suba");
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return
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BinaryOperator::CreateMul(Sub,
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ConstantInt::get(X->getType(), PosVal));
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}
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}
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}
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@ -2,18 +2,14 @@
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; RUN: opt -S -instcombine < %s | FileCheck %s
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target triple = "x86_64-apple-macosx10.6.6"
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define zeroext i16 @foo(i32 %on_off, i16* %puls) nounwind uwtable ssp {
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define zeroext i16 @foo1(i32 %on_off) nounwind uwtable ssp {
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entry:
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%on_off.addr = alloca i32, align 4
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%puls.addr = alloca i16*, align 8
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%a = alloca i32, align 4
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store i32 %on_off, i32* %on_off.addr, align 4
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store i16* %puls, i16** %puls.addr, align 8
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%tmp = load i32* %on_off.addr, align 4
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; CHECK-NOT: sub
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; CHECK-NOT: mul
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; (1 - %tmp) * (-2) -> (%tmp - 1) * 2
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%sub = sub i32 1, %tmp
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; CHECK-NOT: mul i32
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%mul = mul i32 %sub, -2
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; CHECK: shl
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; CHECK-NEXT: add
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@ -22,3 +18,40 @@ entry:
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%conv = trunc i32 %tmp1 to i16
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ret i16 %conv
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}
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define zeroext i16 @foo2(i32 %on_off, i32 %q) nounwind uwtable ssp {
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entry:
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%on_off.addr = alloca i32, align 4
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%q.addr = alloca i32, align 4
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%a = alloca i32, align 4
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store i32 %on_off, i32* %on_off.addr, align 4
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store i32 %q, i32* %q.addr, align 4
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%tmp = load i32* %q.addr, align 4
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%tmp1 = load i32* %on_off.addr, align 4
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%sub = sub i32 %tmp, %tmp1
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; CHECK-NOT: mul i32
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%mul = mul i32 %sub, -4
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; CHECK: sub i32
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; CHECK-NEXT: shl
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store i32 %mul, i32* %a, align 4
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%tmp2 = load i32* %a, align 4
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%conv = trunc i32 %tmp2 to i16
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ret i16 %conv
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}
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define zeroext i16 @foo3(i32 %on_off) nounwind uwtable ssp {
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entry:
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%on_off.addr = alloca i32, align 4
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%a = alloca i32, align 4
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store i32 %on_off, i32* %on_off.addr, align 4
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%tmp = load i32* %on_off.addr, align 4
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%sub = sub i32 7, %tmp
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; CHECK-NOT: mul i32
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%mul = mul i32 %sub, -4
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; CHECK: shl
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; CHECK-NEXT: add
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store i32 %mul, i32* %a, align 4
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%tmp1 = load i32* %a, align 4
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%conv = trunc i32 %tmp1 to i16
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ret i16 %conv
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}
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