[ConstantFolding] check applicability of AllOnes constant creation first

The getAllOnesValue can only handle things that are bitcast from a
ConstantInt, while here we bitcast through a pointer, so we may see more
complex objects (like Array or Struct).

Differential Revision: https://reviews.llvm.org/D83870

Author: vtjnash

llvm/lib/Analysis/ConstantFolding.cpp

@@ -342,8 +342,12 @@ Constant *llvm::ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
     // pointers legally).
     if (C->isNullValue() && !DestTy->isX86_MMXTy())
       return Constant::getNullValue(DestTy);
-    if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() &&
-        !DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types!
+    if (C->isAllOnesValue() &&
+        (DestTy->isIntegerTy() || DestTy->isFloatingPointTy() ||
+         DestTy->isVectorTy()) &&
+        !DestTy->isX86_MMXTy() && !DestTy->isPtrOrPtrVectorTy())
+      // Get ones when the input is trivial, but
+      // only for supported types inside getAllOnesValue.
       return Constant::getAllOnesValue(DestTy);
 
     // If the type sizes are the same and a cast is legal, just directly

llvm/test/Analysis/ConstantFolding/allones.ll

@@ -0,0 +1,46 @@
+; RUN: opt -early-cse -S -o - %s | FileCheck %s
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64-ni:2"
+target triple = "armv7-unknown-linux-gnueabi"
+
+%struct.anon = type { i32 }
+
+@onesstruct = private constant %struct.anon { i32 -1 }, align 4
+
+define i32 @allones_struct() {
+; CHECK-LABEL: @allones_struct()
+; CHECK-NEXT:    %1 = load [1 x i32], [1 x i32]* bitcast (%struct.anon* @onesstruct to [1 x i32]*), align 4
+; CHECK-NEXT:    %2 = extractvalue [1 x i32] %1, 0
+; CHECK-NEXT:    ret i32 %2
+  %1 = load [1 x i32], [1 x i32]* bitcast (%struct.anon* @onesstruct to [1 x i32]*), align 4
+  %2 = extractvalue [1 x i32] %1, 0
+  ret i32 %2
+}
+
+define i32 @allones_int() {
+; CHECK-LABEL: @allones_int()
+; CHECK-NEXT:    ret i32 -1
+  %1 = load i32, i32* bitcast (%struct.anon* @onesstruct to i32*), align 4
+  ret i32 %1
+}
+
+define i32* @allones_ptr() {
+; CHECK-LABEL: @allones_ptr()
+; CHECK-NEXT:    ret i32* inttoptr (i32 -1 to i32*)
+  %1 = load i32*, i32** bitcast (%struct.anon* @onesstruct to i32**), align 4
+  ret i32* %1
+}
+
+define i32 addrspace(1)* @allones_ptr1() {
+; CHECK-LABEL: @allones_ptr1()
+; CHECK-NEXT:    ret i32 addrspace(1)* inttoptr (i32 -1 to i32 addrspace(1)*)
+  %1 = load i32 addrspace(1)*, i32 addrspace(1)** bitcast (%struct.anon* @onesstruct to i32 addrspace(1)**), align 4
+  ret i32 addrspace(1)* %1
+}
+
+define i32 addrspace(2)* @allones_ptr2() {
+; CHECK-LABEL: @allones_ptr2()
+; CHECK-NEXT:    %1 = load i32 addrspace(2)*, i32 addrspace(2)** bitcast (%struct.anon* @onesstruct to i32 addrspace(2)**), align 4
+; CHECK-NEXT:    ret i32 addrspace(2)* %1
+  %1 = load i32 addrspace(2)*, i32 addrspace(2)** bitcast (%struct.anon* @onesstruct to i32 addrspace(2)**), align 4
+  ret i32 addrspace(2)* %1
+}