This implements a more optimal algorithm for selecting a base constant in

constant hoisting. It not only takes into account the number of uses and the
cost of expressions in which constants appear, but now also the resulting
integer range of the offsets. Thus, the algorithm maximizes the number of uses
within an integer range that will enable more efficient code generation. On
ARM, for example, this will enable code size optimisations because less
negative offsets will be created. Negative offsets/immediates are not supported
by Thumb1 thus preventing more compact instruction encoding.

Differential Revision: http://reviews.llvm.org/D21183

llvm-svn: 275382

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/TargetTransformInfo.cpp b/llvm/lib/Analysis/TargetTransformInfo.cpp
index 55b50ae..52013f7 100644
--- a/llvm/lib/Analysis/TargetTransformInfo.cpp
+++ b/llvm/lib/Analysis/TargetTransformInfo.cpp
@@ -209,6 +209,14 @@ int TargetTransformInfo::getFPOpCost(Type *Ty) const {
   return Cost;
 }
 
+int TargetTransformInfo::getIntImmCodeSizeCost(unsigned Opcode, unsigned Idx,
+                                               const APInt &Imm,
+                                               Type *Ty) const {
+  int Cost = TTIImpl->getIntImmCodeSizeCost(Opcode, Idx, Imm, Ty);
+  assert(Cost >= 0 && "TTI should not produce negative costs!");
+  return Cost;
+}
+
 int TargetTransformInfo::getIntImmCost(const APInt &Imm, Type *Ty) const {
   int Cost = TTIImpl->getIntImmCost(Imm, Ty);
   assert(Cost >= 0 && "TTI should not produce negative costs!");