Emit a more efficient magic number multiplication for exact sdivs.

We have to do this in DAGBuilder instead of DAGCombiner, because the exact bit is lost after building.

  struct foo { char x[24]; };
  long bar(struct foo *a, struct foo *b) { return a-b; }
is now compiled into
  movl	4(%esp), %eax
  subl	8(%esp), %eax
  sarl	$3, %eax
  imull	$-1431655765, %eax, %eax
instead of
  movl	4(%esp), %eax
  subl	8(%esp), %eax
  movl	$715827883, %ecx
  imull	%ecx
  movl	%edx, %eax
  shrl	$31, %eax
  sarl	$2, %edx
  addl	%eax, %edx
  movl	%edx, %eax

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134695 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index a1ca891148..a0884ebf5d 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -467,7 +467,7 @@ private:
   void visitSRem(const User &I) { visitBinary(I, ISD::SREM); }
   void visitFRem(const User &I) { visitBinary(I, ISD::FREM); }
   void visitUDiv(const User &I) { visitBinary(I, ISD::UDIV); }
-  void visitSDiv(const User &I) { visitBinary(I, ISD::SDIV); }
+  void visitSDiv(const User &I);
   void visitFDiv(const User &I) { visitBinary(I, ISD::FDIV); }
   void visitAnd (const User &I) { visitBinary(I, ISD::AND); }
   void visitOr  (const User &I) { visitBinary(I, ISD::OR); }