[LLVM][SROA] Teach SROA how to "bitcast" between fixed and scalable vectors. (#130973)

For function whose vscale_range is limited to a single value we can size
scalable vectors. This aids SROA by allowing scalable vector load and
store operations to be considered for replacement whereby bitcasts
through memory can be replaced by vector insert or extract operations.

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index 63665d8..493dec7 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -1165,6 +1165,18 @@ bool Function::nullPointerIsDefined() const {
   return hasFnAttribute(Attribute::NullPointerIsValid);
 }
 
+unsigned Function::getVScaleValue() const {
+  Attribute Attr = getFnAttribute(Attribute::VScaleRange);
+  if (!Attr.isValid())
+    return 0;
+
+  unsigned VScale = Attr.getVScaleRangeMin();
+  if (VScale && VScale == Attr.getVScaleRangeMax())
+    return VScale;
+
+  return 0;
+}
+
 bool llvm::NullPointerIsDefined(const Function *F, unsigned AS) {
   if (F && F->nullPointerIsDefined())
     return true;