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When inferring the pointer alignment, if the global doesn't have an initializer 

and the alignment is 0 (i.e., it's defined globally in one file and declared in
another file) it could get an alignment which is larger than the ABI allows for
that type, resulting in aligned moves being used for unaligned loads.

For instance, in file A.c:

   struct S s;

In file B.c:
   struct {
     // something long
   };
   extern S s;

   void foo() {
     struct S p = s;
     // ...
   }

this copy is a 'memcpy' which is turned into a series of 'movaps' instructions
on X86. But this is wrong, because 'struct S' has alignment of 4, not 16.

llvm-svn: 140902
This commit is contained in:
Bill Wendling 2011-09-30 23:19:55 +00:00
parent f56c0137e2
commit 9925f197cc
2 changed files with 28 additions and 0 deletions
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2
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -6537,6 +6537,8 @@ unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) const {
Align = TD->getPreferredAlignment(GVar);
}
}
if (!Align)
Align = TLI.getTargetData()->getABITypeAlignment(GV->getType());
}
return MinAlign(Align, GVOffset);
}

26
llvm/test/CodeGen/X86/alignment-2.ll Normal file
View File

@ -0,0 +1,26 @@
; RUN: llc < %s -mtriple i386-apple-darwin10 | not grep movaps
; <rdar://problem/10058036>
%struct._psqlSettings = type { %struct.pg_conn*, i32, %struct.__sFILE*, i8, %struct.printQueryOpt, i8*, i8, i32, %struct.__sFILE*, i8, i32, i8*, i8*, i8*, i64, i8, %struct.__sFILE*, %struct._variable*, i8, i8, i8, i8, i8, i32, i32, i32, i32, i32, i8*, i8*, i8*, i32 }
%struct.pg_conn = type opaque
%struct.__sFILE = type { i8*, i32, i32, i16, i16, %struct.__sbuf, i32, i8*, i32 (i8*)*, i32 (i8*, i8*, i32)*, i64 (i8*, i64, i32)*, i32 (i8*, i8*, i32)*, %struct.__sbuf, %struct.__sFILEX*, i32, [3 x i8], [1 x i8], %struct.__sbuf, i32, i64 }
%struct.__sbuf = type { i8*, i32 }
%struct.__sFILEX = type opaque
%struct.printQueryOpt = type { %struct.printTableOpt, i8*, i8, i8*, i8**, i8, i8, i8* }
%struct.printTableOpt = type { i32, i8, i16, i16, i8, i8, i8, i32, %struct.printTextFormat*, i8*, i8*, i8, i8*, i32, i32, i32 }
%struct.printTextFormat = type { i8*, [4 x %struct.printTextLineFormat], i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8*, i8 }
%struct.printTextLineFormat = type { i8*, i8*, i8*, i8* }
%struct._variable = type { i8*, i8*, void (i8*)*, %struct._variable* }
%struct.pg_result = type opaque
@pset = external global %struct._psqlSettings
define signext i8 @do_lo_list() nounwind optsize ssp {
bb:
%myopt = alloca %struct.printQueryOpt, align 4
%tmp = bitcast %struct.printQueryOpt* %myopt to i8*
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %tmp, i8* bitcast (%struct.printQueryOpt* getelementptr inbounds (%struct._psqlSettings* @pset, i32 0, i32 4) to i8*), i32 76, i32 4, i1 false)
ret i8 0
}
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind