SelectionDAGISel doesn't handle illegal vectors of illegal types right

[llvmbot]

Bugzilla Link	1132
Resolution	FIXED
Resolved on	May 05, 2008 11:34
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@lattner,@isanbard,@sunfishcode,@nlewycky

Extended Description

NODE: 0x120b12b80: i16 = Register #​1024
llc: LegalizeDAG.cpp:3089:
llvm::SDOperand::SelectionDAGLegalize::PromoteOp(llvm::SDOperand):
Assertion `0 && "Do not know how to promote this operator!"' failed.

For

; ModuleID = 'bugpoint-reduced-simplified.bc'
target datalayout = "e-p:64:64"
target endian = little
target pointersize = 64
target triple = "alphaev6-unknown-linux-gnu"

implementation ; Functions:

define void %main() {
entry:
br label %bb

bb: ; preds = %bb, %entry
br i1 false, label %bb26, label %bb

bb19: ; preds = %bb26
ret void

bb26: ; preds = %bb
br i1 false, label %bb30, label %bb19

bb30: ; preds = %bb26
br label %bb45

bb45: ; preds = %bb45, %bb30
%V.0 = phi <8 x i16> [ %tmp42, %bb45 ], [ zeroinitializer, %bb30 ]
; <<8 x i16>> [#uses=1]
%tmp42 = mul <8 x i16> zeroinitializer, %V.0 ; <<8 x i16>>
[#uses=1]
br label %bb45
}

[lattner]

The problem is that SDISel sees that the vector isn't legal, so it turns it into a bunch of scalar values.
However, it doesn't do the correct promotion/expansion that it is supposed to do, so the initial dag it
creates has bad copyto/fromreg nodes.

This can be seen on alpha or ppc:

$ llc t2.bc -o - -march=ppc32 -mcpu=g3

Presumably it also affects X86-32 if you use <2 x i64> with an i386 target cpu.

-Chris

[sunfishcode]

I believe this PR is fixed by r37781 and ensuing changes. At least, the testcase
compiles without abort with all of the targets mentioned here.

[sunfishcode]

However, changing the testcase to use <2 x i64> on i386 as suggested above
still gets abort. It gets the following abort:

NODE: 0x8b3f180: i64 = extract_vector_elt 0x8b3eaa8, 0x8b3f118
llc: /.AUTO/bwraid/usr.people/djg/svn/test/official.llvm/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:4801: void::SelectionDAGLegalize::ExpandOp(llvm::SDOperand, llvm::SDOperand&, llvm::SDOperand&): Assertion `0 && "Do not know how to expand this operator!"' failed.

[sunfishcode]

The support for copying to/from virtual registers is now more
flexible, and this testcase now works even on i386 with <2 x i64>.