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InstSimplify: X >> X -> 0

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185973 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2013-07-09 22:01:22 +00:00
parent e4e742a62d
commit 8c5c6f0e09
3 changed files with 27 additions and 3 deletions
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8
lib/Analysis/InstructionSimplify.cpp
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@@ -1363,6 +1363,10 @@ static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, Q, MaxRecurse)) if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, Q, MaxRecurse))
return V; return V;
// X >> X -> 0
if (Op0 == Op1)
return Constant::getNullValue(Op0->getType());
// undef >>l X -> 0 // undef >>l X -> 0
if (match(Op0, m_Undef())) if (match(Op0, m_Undef()))
return Constant::getNullValue(Op0->getType()); return Constant::getNullValue(Op0->getType());
@@ -1391,6 +1395,10 @@ static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, Q, MaxRecurse)) if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, Q, MaxRecurse))
return V; return V;
// X >> X -> 0
if (Op0 == Op1)
return Constant::getNullValue(Op0->getType());
// all ones >>a X -> all ones // all ones >>a X -> all ones
if (match(Op0, m_AllOnes())) if (match(Op0, m_AllOnes()))
return Op0; return Op0;

6
test/Transforms/InstCombine/div-shift.ll
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@@ -54,9 +54,9 @@ define i32 @t5(i1 %x, i1 %y, i32 %V) nounwind {
; CHECK: t5 ; CHECK: t5
; CHECK-NOT: udiv ; CHECK-NOT: udiv
; CHECK-NEXT: [[SEL1:%.*]] = select i1 %x, i32 5, i32 6 ; CHECK-NEXT: [[SEL1:%.*]] = select i1 %x, i32 5, i32 6
; CHECK-NEXT: [[SEL2:%.*]] = select i1 %y, i32 [[SEL1]], i32 %V ; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 %V, [[SEL1]]
; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 %V, [[SEL2]] ; CHECK-NEXT: [[SEL2:%.*]] = select i1 %y, i32 [[LSHR]], i32 0
; CHECK-NEXT: ret i32 [[LSHR]] ; CHECK-NEXT: ret i32 [[SEL2]]
%1 = shl i32 1, %V %1 = shl i32 1, %V
%2 = select i1 %x, i32 32, i32 64 %2 = select i1 %x, i32 32, i32 64
%3 = select i1 %y, i32 %2, i32 %1 %3 = select i1 %y, i32 %2, i32 %1

16
test/Transforms/InstSimplify/compare.ll
View File

@@ -357,6 +357,14 @@ define i1 @lshr2(i32 %x) {
; CHECK: ret i1 false ; CHECK: ret i1 false
} }
define i1 @lshr3(i32 %x) {
; CHECK: @lshr3
%s = lshr i32 %x, %x
%c = icmp eq i32 %s, 0
ret i1 %c
; CHECK: ret i1 true
}
define i1 @ashr1(i32 %x) { define i1 @ashr1(i32 %x) {
; CHECK: @ashr1 ; CHECK: @ashr1
%s = ashr i32 -1, %x %s = ashr i32 -1, %x
@@ -373,6 +381,14 @@ define i1 @ashr2(i32 %x) {
; CHECK: ret i1 false ; CHECK: ret i1 false
} }
define i1 @ashr3(i32 %x) {
; CHECK: @ashr3
%s = ashr i32 %x, %x
%c = icmp eq i32 %s, 0
ret i1 %c
; CHECK: ret i1 true
}
define i1 @select1(i1 %cond) { define i1 @select1(i1 %cond) {
; CHECK: @select1 ; CHECK: @select1
%s = select i1 %cond, i32 1, i32 0 %s = select i1 %cond, i32 1, i32 0