[PATCH] D112142: [InstCombine][ConstantFolding] Make ConstantFoldLoadThroughBitcast TypeSize-aware

[Peter Waller via Phabricator via llvm-commits]

peterwaller-arm updated this revision to Diff 381191.
peterwaller-arm added a comment.

- Fix typesize query to use !isKnownGE.
- Add a negative test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112142/new/

https://reviews.llvm.org/D112142

Files:
  llvm/lib/Analysis/ConstantFolding.cpp
  llvm/test/Transforms/InstCombine/vscale_load.ll


Index: llvm/test/Transforms/InstCombine/vscale_load.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/vscale_load.ll
@@ -0,0 +1,29 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S -verify | FileCheck %s
+
+define <2 x i8> @constprop_load_bitcast() {
+; CHECK-LABEL: @constprop_load_bitcast(
+; CHECK-NEXT:    ret <2 x i8> zeroinitializer
+;
+  %stack_var = alloca <vscale x 16 x i1>, align 16
+  store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* %stack_var, align 16
+  %cast_to_fixed = bitcast <vscale x 16 x i1>* %stack_var to <2 x i8>*
+  %a = load <2 x i8>, <2 x i8>* %cast_to_fixed, align 16
+  ret <2 x i8> %a
+}
+
+; vscale-sized vec not guaranteed to fill destination.
+define <8 x i8> @constprop_load_bitcast_neg() {
+; CHECK-LABEL: @constprop_load_bitcast_neg(
+; CHECK-NEXT:    [[STACK_VAR:%.*]] = alloca <vscale x 16 x i1>, align 16
+; CHECK-NEXT:    store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* [[STACK_VAR]], align 16
+; CHECK-NEXT:    [[CAST_TO_FIXED:%.*]] = bitcast <vscale x 16 x i1>* [[STACK_VAR]] to <8 x i8>*
+; CHECK-NEXT:    [[A:%.*]] = load <8 x i8>, <8 x i8>* [[CAST_TO_FIXED]], align 16
+; CHECK-NEXT:    ret <8 x i8> [[A]]
+;
+  %stack_var = alloca <vscale x 16 x i1>, align 16
+  store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* %stack_var, align 16
+  %cast_to_fixed = bitcast <vscale x 16 x i1>* %stack_var to <8 x i8>*
+  %a = load <8 x i8>, <8 x i8>* %cast_to_fixed, align 16
+  ret <8 x i8> %a
+}
Index: llvm/lib/Analysis/ConstantFolding.cpp
===================================================================
--- llvm/lib/Analysis/ConstantFolding.cpp
+++ llvm/lib/Analysis/ConstantFolding.cpp
@@ -352,9 +352,9 @@
                                          const DataLayout &DL) {
   do {
     Type *SrcTy = C->getType();
-    uint64_t DestSize = DL.getTypeSizeInBits(DestTy);
-    uint64_t SrcSize = DL.getTypeSizeInBits(SrcTy);
-    if (SrcSize < DestSize)
+    TypeSize DestSize = DL.getTypeSizeInBits(DestTy);
+    TypeSize SrcSize = DL.getTypeSizeInBits(SrcTy);
+    if (!TypeSize::isKnownGE(SrcSize, DestSize))
       return nullptr;
 
     // Catch the obvious splat cases (since all-zeros can coerce non-integral


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