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Look pass zext to strength reduce an udiv. Patch by David Majnemer. rdar://11721329 

llvm-svn: 158946
This commit is contained in:
Evan Cheng 2012-06-21 22:52:49 +00:00
parent 26f5a62712
commit 32c7cc8ec9
3 changed files with 27 additions and 10 deletions
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5
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -464,9 +464,12 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
{ const APInt *CI; Value *N;
if (match(Op1, m_Shl(m_Power2(CI), m_Value(N)))) {
if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) ||
match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) {
if (*CI != 1)
N = Builder->CreateAdd(N, ConstantInt::get(I.getType(),CI->logBase2()));
if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
N = Builder->CreateZExt(N, Z->getDestTy());
if (I.isExact())
return BinaryOperator::CreateExactLShr(Op0, N);
return BinaryOperator::CreateLShr(Op0, N);

23
llvm/test/Transforms/InstCombine/div-shift.ll Normal file
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@ -0,0 +1,23 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
define i32 @t1(i16 zeroext %x, i32 %y) nounwind {
entry:
; CHECK: t1
; CHECK-NOT: sdiv
; CHECK: lshr i32 %conv
%conv = zext i16 %x to i32
%s = shl i32 2, %y
%d = sdiv i32 %conv, %s
ret i32 %d
}
; rdar://11721329
define i64 @t2(i64 %x, i32 %y) nounwind {
; CHECK: t2
; CHECK-NOT: udiv
; CHECK: lshr i64 %x
%1 = shl i32 1, %y
%2 = zext i32 %1 to i64
%3 = udiv i64 %x, %2
ret i64 %3
}

9
llvm/test/Transforms/InstCombine/sdiv-shift.ll
View File

@ -1,9 +0,0 @@
; RUN: opt < %s -instcombine -S | not grep div
define i32 @a(i16 zeroext %x, i32 %y) nounwind {
entry:
%conv = zext i16 %x to i32
%s = shl i32 2, %y
%d = sdiv i32 %conv, %s
ret i32 %d
}