// sdiv X, -1 == -X
if (RHS->isAllOnesValue())
return BinaryOperator::CreateNeg(*Context, Op0);
+
+ // sdiv X, C --> ashr X, log2(C)
+ if (cast<SDivOperator>(&I)->isExact() &&
+ RHS->getValue().isNonNegative() &&
+ RHS->getValue().isPowerOf2()) {
+ Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
+ RHS->getValue().exactLogBase2());
+ return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName());
+ }
}
// If the sign bits of both operands are zero (i.e. we can prove they are
--- /dev/null
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | FileCheck %s
+
+; CHECK: define i32 @foo
+; CHECK: sdiv i32 %x, 8
+define i32 @foo(i32 %x) {
+ %y = sdiv i32 %x, 8
+ ret i32 %y
+}
+
+; CHECK: define i32 @bar
+; CHECK: ashr i32 %x, 3
+define i32 @bar(i32 %x) {
+ %y = sdiv exact i32 %x, 8
+ ret i32 %y
+}