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| author | Dan Gohman <gohman@apple.com> | 2009-03-24 01:04:34 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2009-03-24 01:04:34 +0000 |
| commit | a96dc14968ded9d4cff2382696cfdb6e40173e8a (patch) | |
| tree | ec3900e32c0df1cbfb88dcbb2cf4e57409d7de49 /lib/Target/X86/X86CallingConv.td | |
| parent | 8f4aa333d02d0f48f90f4604d894a73ee53edcb5 (diff) | |
| download | llvm-a96dc14968ded9d4cff2382696cfdb6e40173e8a.tar.gz llvm-a96dc14968ded9d4cff2382696cfdb6e40173e8a.tar.bz2 llvm-a96dc14968ded9d4cff2382696cfdb6e40173e8a.tar.xz | |
I was convinced that it's ok to allow a second i8 return value
to be returned in DL. LLVM's multiple-return-value support is
not ABI-conforming; front-ends that wish to have code emitted
that conforms to an ABI are currently expected to make
arrangements for this on their own rather than assuming that
multiple-return-values will automatically do the right thing.
This commit doesn't fundamentally change this situation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67588 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/X86/X86CallingConv.td')
| -rw-r--r-- | lib/Target/X86/X86CallingConv.td | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td index 6924520ab8..7f99203a83 100644 --- a/lib/Target/X86/X86CallingConv.td +++ b/lib/Target/X86/X86CallingConv.td @@ -22,13 +22,14 @@ class CCIfSubtarget<string F, CCAction A> // Return-value conventions common to all X86 CC's. def RetCC_X86Common : CallingConv<[ - // Scalar values are returned in AX first, then DX, except for i8 where - // the convention is to return values in AL and AH. However, using AL and - // AH is problematic -- a return of {i16,i8} would end up using AX and AH, - // and one value would clobber the other. C front-ends are currently expected - // to pack two i8 values into an i16 in the rare situations where this - // is necessary. - CCIfType<[i8] , CCAssignToReg<[AL]>>, + // Scalar values are returned in AX first, then DX. For i8, the ABI + // requires the values to be in AL and AH, however this code uses AL and DL + // instead. This is because using AH for the second register conflicts with + // the way LLVM does multiple return values -- a return of {i16,i8} would end + // up in AX and AH, which overlap. Front-ends wishing to conform to the ABI + // for functions that return two i8 values are currently expected to pack the + // values into an i16 (which uses AX, and thus AL:AH). + CCIfType<[i8] , CCAssignToReg<[AL, DL]>>, CCIfType<[i16], CCAssignToReg<[AX, DX]>>, CCIfType<[i32], CCAssignToReg<[EAX, EDX]>>, CCIfType<[i64], CCAssignToReg<[RAX, RDX]>>, |