llvm/test/Transforms/InstCombine/constant-fold-alias.ll

; RUN: opt -S < %s -instcombine | FileCheck %s

target datalayout = "e-p1:16:16-p2:32:32-p3:64:64"

@G1 = global i32 42, align 1
@G2 = global i32 42
@G3 = global [4 x i8] zeroinitializer, align 1

@A1 = alias i32, bitcast (i8* getelementptr inbounds ([4 x i8], [4 x i8]* @G3, i32 0, i32 2) to i32*)
@A2 = alias i32, inttoptr (i64 and (i64 ptrtoint (i8* getelementptr inbounds ([4 x i8], [4 x i8]* @G3, i32 0, i32 3) to i64), i64 -4) to i32*)

define i64 @f1() {
; This cannot be constant folded because G1 is underaligned.
; CHECK-LABEL: @f1(
; CHECK: ret i64 and
  ret i64 and (i64 ptrtoint (i32* @G1 to i64), i64 1)
}

define i64 @f2() {
; The preferred alignment for G2 allows this one to foled to zero.
; CHECK-LABEL: @f2(
; CHECK: ret i64 0
  ret i64 and (i64 ptrtoint (i32* @G2 to i64), i64 1)
}

define i64 @g1() {
; This cannot be constant folded because A1 aliases G3 which is underalaigned.
; CHECK-LABEL: @g1(
; CHECK: ret i64 and
  ret i64 and (i64 ptrtoint (i32* @A1 to i64), i64 1)
}

define i64 @g2() {
; While A2 also aliases G3 which is underaligned, the math of A2 forces a
; certain alignment allowing this to fold to zero.
; CHECK-LABEL: @g2(
; CHECK: ret i64 0
  ret i64 and (i64 ptrtoint (i32* @A2 to i64), i64 1)
}