[PATCH] D71389: [ConstantFold][SVE] Fix constant folding for bitcast.

[Huihui Zhang via Phabricator via llvm-commits]

huihuiz created this revision.
huihuiz added reviewers: sdesmalen, huntergr, spatel, lebedev.ri, apazos, efriedma, willlovett.
huihuiz added a project: LLVM.
Herald added subscribers: psnobl, rkruppe, hiraditya, tschuett.

Should not constant fold bitcast instruction for scalable vector type.

Continuation work of D70985 <https://reviews.llvm.org/D70985>, D71147 <https://reviews.llvm.org/D71147>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71389

Files:
  llvm/lib/IR/ConstantFold.cpp
  llvm/test/Analysis/ConstantFolding/bitcast.ll


Index: llvm/test/Analysis/ConstantFolding/bitcast.ll
===================================================================
--- /dev/null
+++ llvm/test/Analysis/ConstantFolding/bitcast.ll
@@ -0,0 +1,12 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -constprop -S | FileCheck %s
+
+define <vscale x 4 x float> @bitcast_scalable_constant() {
+; CHECK-LABEL: @bitcast_scalable_constant(
+; CHECK-NEXT:    ret <vscale x 4 x float> bitcast (<vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 1, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer) to <vscale x 4 x float>)
+;
+  %i1 = insertelement <vscale x 4 x i32> undef, i32 1, i32 0
+  %i2 = shufflevector <vscale x 4 x i32> %i1, <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer
+  %i3 = bitcast <vscale x 4 x i32> %i2 to <vscale x 4 x float>
+  ret <vscale x 4 x float> %i3
+}
Index: llvm/lib/IR/ConstantFold.cpp
===================================================================
--- llvm/lib/IR/ConstantFold.cpp
+++ llvm/lib/IR/ConstantFold.cpp
@@ -47,6 +47,11 @@
   if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
   if (CV->isNullValue()) return Constant::getNullValue(DstTy);
 
+  // Do not iterate on scalable vector. The num of elements is unknown at
+  // compile-time.
+  if (DstTy->isScalable())
+    return nullptr;
+
   // If this cast changes element count then we can't handle it here:
   // doing so requires endianness information.  This should be handled by
   // Analysis/ConstantFolding.cpp


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