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-rw-r--r--lib/Transforms/InstCombine/InstCombineMulDivRem.cpp25
-rw-r--r--test/Transforms/InstCombine/2011-05-28-swapmulsub.ll45
2 files changed, 55 insertions, 15 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 94b619b203..b860440f60 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -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));
}
}
}
diff --git a/test/Transforms/InstCombine/2011-05-28-swapmulsub.ll b/test/Transforms/InstCombine/2011-05-28-swapmulsub.ll
index e4417ef96a..b096d1f952 100644
--- a/test/Transforms/InstCombine/2011-05-28-swapmulsub.ll
+++ b/test/Transforms/InstCombine/2011-05-28-swapmulsub.ll
@@ -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
+}