From 98f08752f76b80a509037986d620b402c48f5115 Mon Sep 17 00:00:00 2001
From: Peter Waller <peter.waller@arm.com>
Date: Thu, 28 Oct 2021 12:14:52 +0000
Subject: [PATCH] [InstCombine][ConstantFolding] Make
 ConstantFoldLoadThroughBitcast TypeSize-aware

The newly added test previously caused the compiler to fail an
assertion. It looks like a strightforward TypeSize upgrade.

Reviewed By: paulwalker-arm

Differential Revision: https://reviews.llvm.org/D112142
---
 llvm/lib/Analysis/ConstantFolding.cpp           |  6 +++---
 llvm/test/Transforms/InstCombine/vscale_load.ll | 27 +++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 llvm/test/Transforms/InstCombine/vscale_load.ll

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 4cc3fcd..3ed3b89 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -352,9 +352,9 @@ Constant *llvm::ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
                                          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
diff --git a/llvm/test/Transforms/InstCombine/vscale_load.ll b/llvm/test/Transforms/InstCombine/vscale_load.ll
new file mode 100644
index 0000000..4041ffc
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/vscale_load.ll
@@ -0,0 +1,27 @@
+; 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(<vscale x 16 x i1>* %ptr) {
+; CHECK-LABEL: @constprop_load_bitcast(
+; CHECK-NEXT:    store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* [[PTR:%.*]], align 16
+; CHECK-NEXT:    ret <2 x i8> zeroinitializer
+;
+  store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* %ptr, align 16
+  %cast_to_fixed = bitcast <vscale x 16 x i1>* %ptr 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(<vscale x 16 x i1>* %ptr) {
+; CHECK-LABEL: @constprop_load_bitcast_neg(
+; CHECK-NEXT:    store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* [[PTR:%.*]], align 16
+; CHECK-NEXT:    [[CAST_TO_FIXED:%.*]] = bitcast <vscale x 16 x i1>* [[PTR]] 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]]
+;
+  store <vscale x 16 x i1> zeroinitializer, <vscale x 16 x i1>* %ptr, align 16
+  %cast_to_fixed = bitcast <vscale x 16 x i1>* %ptr to <8 x i8>*
+  %a = load <8 x i8>, <8 x i8>* %cast_to_fixed, align 16
+  ret <8 x i8> %a
+}
-- 
2.7.4