[LLVMbugs] [Bug 8180] New: TD alignment's treatment in struct differs among InstCombine and CodeGen

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=8180

           Summary: TD alignment's treatment in struct differs among
                    InstCombine and CodeGen
           Product: new-bugs
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: geek4civic at gmail.com
                CC: llvmbugs at cs.uiuc.edu


Consider the IR below;

target datalayout =
"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
%st = type {i8, double}
define double* @foo() {
entry:
  %p = getelementptr %st* null,i32 0,i32 1
  ret double* %p
}


$ opt -instcombine | llc (f64:32:64)
_foo:
        movl    $4, %eax

$ opt -instcombine | llc (f64:64:64)
_foo:
        movl    $8, %eax

$ opt | llc (f64:64:64)
_foo:
        movl    $4, %eax


On i686-linux, TD contains "f64:32:64".

On powerpc-linux and cygming, f64 ABI alignment is 64(f64:64:64), thus I saw
different results.

FYI, it seems clang relies on ABI alignments.

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