[PATCH] D135249: [AggressiveInstCombine] Fix cases where non-opaque pointers are used

[David Stuttard via Phabricator via llvm-commits]

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In the case of non-opaque pointers, when combining consecutive loads,
need to bitcast the pointer source to the combined type size, otherwise
asserts are triggered.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135249

Files:
  llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
  llvm/test/Transforms/AggressiveInstCombine/X86/non-opaque-or-load.ll


Index: llvm/test/Transforms/AggressiveInstCombine/X86/non-opaque-or-load.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/AggressiveInstCombine/X86/non-opaque-or-load.ll
@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=aggressive-instcombine -mtriple x86_64-none-eabi -mattr=avx2 -data-layout="e-n64" -S | FileCheck %s --check-prefixes=LE
+; RUN: opt < %s -passes=aggressive-instcombine -mtriple x86_64-none-eabi -mattr=avx2 -data-layout="E-n64" -S | FileCheck %s --check-prefixes=BE
+
+define i16 @loadCombine_2consecutive(i8* %p) {
+;
+; LE-LABEL: @loadCombine_2consecutive(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast i8* [[P:%.*]] to i16*
+; LE-NEXT:    [[L1:%.*]] = load i16, i16* [[TMP1]], align 1
+; LE-NEXT:    ret i16 [[L1]]
+;
+; BE-LABEL: @loadCombine_2consecutive(
+; BE-NEXT:    [[P1:%.*]] = getelementptr i8, i8* [[P:%.*]], i32 1
+; BE-NEXT:    [[L1:%.*]] = load i8, i8* [[P]], align 1
+; BE-NEXT:    [[L2:%.*]] = load i8, i8* [[P1]], align 1
+; BE-NEXT:    [[E1:%.*]] = zext i8 [[L1]] to i16
+; BE-NEXT:    [[E2:%.*]] = zext i8 [[L2]] to i16
+; BE-NEXT:    [[S2:%.*]] = shl i16 [[E2]], 8
+; BE-NEXT:    [[O1:%.*]] = or i16 [[E1]], [[S2]]
+; BE-NEXT:    ret i16 [[O1]]
+;
+  %p1 = getelementptr i8, i8* %p, i32 1
+  %l1 = load i8, i8* %p
+  %l2 = load i8, i8* %p1
+  %e1 = zext i8 %l1 to i16
+  %e2 = zext i8 %l2 to i16
+  %s2 = shl i16 %e2, 8
+  %o1 = or i16 %e1, %s2
+  ret i16 %o1
+}
Index: llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
===================================================================
--- llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
+++ llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
@@ -811,6 +811,15 @@
   // New load can be generated
   Value *Load1Ptr = LI1->getPointerOperand();
   Builder.SetInsertPoint(LI1);
+  if (!cast<PointerType>(Load1Ptr->getType())->isOpaque()) {
+    // We require an extra bitcast for non-opaque cases
+    unsigned Load1AS =
+        cast<PointerType>(Load1Ptr->getType())->getAddressSpace();
+    Load1Ptr = Builder.CreateBitCast(
+        Load1Ptr,
+        PointerType::get(
+            IntegerType::get(Load1Ptr->getContext(), LOps.LoadSize), Load1AS));
+  }
   NewLoad = Builder.CreateAlignedLoad(
       IntegerType::get(Load1Ptr->getContext(), LOps.LoadSize), Load1Ptr,
       LI1->getAlign(), LI1->isVolatile(), "");


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