PNaCl: Fix FlattenGlobals to correctly handle implicitly-aligned variables

test/Transforms/NaCl/flatten-globals.ll

 ; RUN: opt -flatten-globals %s -S | FileCheck %s
 ; RUN: opt -flatten-globals %s -S | FileCheck %s -check-prefix=CLEANED
 
 target datalayout = "p:32:32:32"
 
 
 ; Check simple cases
 
 @var_i32 = global i32 258
 ; CHECK: @var_i32 = global [4 x i8] c"\02\01\00\00"
@@ skipping 73 matching lines @@
 @weak_external_var = extern_weak global i32
 ; CHECK: @weak_external_var = extern_weak global [4 x i8]
 
 @tls_var = external thread_local global i32
 ; CHECK: @tls_var = external thread_local global [4 x i8]
 
 @aligned_var = global i32 260, align 8
 ; CHECK: @aligned_var = global [4 x i8] c"\04\01\00\00", align 8
 
 
+; Check alignment handling
+
+@implicit_alignment_i32 = global i32 zeroinitializer
+; CHECK: @implicit_alignment_i32 = global [4 x i8] zeroinitializer, align 4
+
+@implicit_alignment_double = global double zeroinitializer
+; CHECK: @implicit_alignment_double = global [8 x i8] zeroinitializer, align 8
+
+; FlattenGlobals is not allowed to increase the alignment of the
+; variable when an explicit section is specified (although PNaCl does
+; not support this attribute).
+@lower_alignment_section = global i32 0, section "mysection", align 1
+; CHECK: @lower_alignment_section = global [4 x i8] zeroinitializer, section "mysection", align 1
+
+; FlattenGlobals could increase the alignment when no section is
+; specified, but it does not.
+@lower_alignment = global i32 0, align 1
+; CHECK: @lower_alignment = global [4 x i8] zeroinitializer, align 1
+
+
 ; Check handling of global references
 
 @var1 = external global i32
 @var2 = external global i8
 
 %ptrs1 = type { i32*, i8*, i32 }
 @ptrs1 = global %ptrs1 { i32* @var1, i8* null, i32 259 }
 ; CHECK: @ptrs1 = global <{ i8*, [8 x i8] }> <{ i8* getelementptr inbounds ([4 x i8]* @var1, i32 0, i32 0), [8 x i8] c"\00\00\00\00\03\01\00\00" }>
 
 %ptrs2 = type { i32, i32*, i8* }
@@ skipping 67 matching lines @@
 }
 ; CHECK: define i32* @get_address() {
 ; CHECK-NEXT: ret i32* bitcast ([4 x i8]* @var_i32 to i32*)
 
 
 define void @func_with_block() {
   br label %label
 label:
   ret void
 }