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[ARM64EC] Fix thunks for C++ methods returning structs. (llvm#95876)
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For C++ methods, the first argument is "this", and the second is the
sret argument, which needs to be returned indirectly. Add handling for
this case.
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@efriedma-quic
efriedma-quic committed Jun 18, 2024
1 parent b932da1 commit b1477eb
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Showing 2 changed files with 64 additions and 8 deletions.
25 changes: 17 additions & 8 deletions llvm/lib/Target/AArch64/AArch64Arm64ECCallLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -209,27 +209,36 @@ void AArch64Arm64ECCallLowering::getThunkRetType(
#endif
if (T->isVoidTy()) {
if (FT->getNumParams()) {
auto SRetAttr = AttrList.getParamAttr(0, Attribute::StructRet);
auto InRegAttr = AttrList.getParamAttr(0, Attribute::InReg);
if (SRetAttr.isValid() && InRegAttr.isValid()) {
Attribute SRetAttr0 = AttrList.getParamAttr(0, Attribute::StructRet);
Attribute InRegAttr0 = AttrList.getParamAttr(0, Attribute::InReg);
Attribute SRetAttr1, InRegAttr1;
if (FT->getNumParams() > 1) {
// Also check the second parameter (for class methods, the first
// parameter is "this", and the second parameter is the sret pointer.)
// It doesn't matter which one is sret.
SRetAttr1 = AttrList.getParamAttr(1, Attribute::StructRet);
InRegAttr1 = AttrList.getParamAttr(1, Attribute::InReg);
}
if ((SRetAttr0.isValid() && InRegAttr0.isValid()) ||
(SRetAttr1.isValid() && InRegAttr1.isValid())) {
// sret+inreg indicates a call that returns a C++ class value. This is
// actually equivalent to just passing and returning a void* pointer
// as the first argument. Translate it that way, instead of trying
// to model "inreg" in the thunk's calling convention, to simplify
// the rest of the code.
// as the first or second argument. Translate it that way, instead of
// trying to model "inreg" in the thunk's calling convention; this
// simplfies the rest of the code, and matches MSVC mangling.
Out << "i8";
Arm64RetTy = I64Ty;
X64RetTy = I64Ty;
return;
}
if (SRetAttr.isValid()) {
if (SRetAttr0.isValid()) {
// FIXME: Sanity-check the sret type; if it's an integer or pointer,
// we'll get screwy mangling/codegen.
// FIXME: For large struct types, mangle as an integer argument and
// integer return, so we can reuse more thunks, instead of "m" syntax.
// (MSVC mangles this case as an integer return with no argument, but
// that's a miscompile.)
Type *SRetType = SRetAttr.getValueAsType();
Type *SRetType = SRetAttr0.getValueAsType();
Align SRetAlign = AttrList.getParamAlignment(0).valueOrOne();
Type *Arm64Ty, *X64Ty;
canonicalizeThunkType(SRetType, SRetAlign, /*Ret*/ true, ArgSizeBytes,
Expand Down
47 changes: 47 additions & 0 deletions llvm/test/CodeGen/AArch64/arm64ec-entry-thunks.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -444,6 +444,50 @@ define %T2 @simple_struct(%T1 %0, %T2 %1, %T3, %T4) nounwind {
ret %T2 %1
}

define void @cxx_method(ptr noundef nonnull align 8 dereferenceable(8) %0, ptr dead_on_unwind inreg noalias writable sret(i64) align 8 %1) {
; CHECK-LABEL: .def $ientry_thunk$cdecl$i8$i8i8;
; CHECK: .section .wowthk$aa,"xr",discard,$ientry_thunk$cdecl$i8$i8i8
; CHECK: // %bb.0:
; CHECK-NEXT: stp q6, q7, [sp, #-176]! // 32-byte Folded Spill
; CHECK-NEXT: .seh_save_any_reg_px q6, 176
; CHECK-NEXT: stp q8, q9, [sp, #32] // 32-byte Folded Spill
; CHECK-NEXT: .seh_save_any_reg_p q8, 32
; CHECK-NEXT: stp q10, q11, [sp, #64] // 32-byte Folded Spill
; CHECK-NEXT: .seh_save_any_reg_p q10, 64
; CHECK-NEXT: stp q12, q13, [sp, #96] // 32-byte Folded Spill
; CHECK-NEXT: .seh_save_any_reg_p q12, 96
; CHECK-NEXT: stp q14, q15, [sp, #128] // 32-byte Folded Spill
; CHECK-NEXT: .seh_save_any_reg_p q14, 128
; CHECK-NEXT: stp x29, x30, [sp, #160] // 16-byte Folded Spill
; CHECK-NEXT: .seh_save_fplr 160
; CHECK-NEXT: add x29, sp, #160
; CHECK-NEXT: .seh_add_fp 160
; CHECK-NEXT: .seh_endprologue
; CHECK-NEXT: blr x9
; CHECK-NEXT: adrp x8, __os_arm64x_dispatch_ret
; CHECK-NEXT: ldr x1, [x8, :lo12:__os_arm64x_dispatch_ret]
; CHECK-NEXT: mov x8, x0
; CHECK-NEXT: .seh_startepilogue
; CHECK-NEXT: ldp x29, x30, [sp, #160] // 16-byte Folded Reload
; CHECK-NEXT: .seh_save_fplr 160
; CHECK-NEXT: ldp q14, q15, [sp, #128] // 32-byte Folded Reload
; CHECK-NEXT: .seh_save_any_reg_p q14, 128
; CHECK-NEXT: ldp q12, q13, [sp, #96] // 32-byte Folded Reload
; CHECK-NEXT: .seh_save_any_reg_p q12, 96
; CHECK-NEXT: ldp q10, q11, [sp, #64] // 32-byte Folded Reload
; CHECK-NEXT: .seh_save_any_reg_p q10, 64
; CHECK-NEXT: ldp q8, q9, [sp, #32] // 32-byte Folded Reload
; CHECK-NEXT: .seh_save_any_reg_p q8, 32
; CHECK-NEXT: ldp q6, q7, [sp], #176 // 32-byte Folded Reload
; CHECK-NEXT: .seh_save_any_reg_px q6, 176
; CHECK-NEXT: .seh_endepilogue
; CHECK-NEXT: br x1
; CHECK-NEXT: .seh_endfunclet
; CHECK-NEXT: .seh_endproc
ret void
}


; Verify the hybrid bitmap
; CHECK-LABEL: .section .hybmp$x,"yi"
; CHECK-NEXT: .symidx "#no_op"
Expand Down Expand Up @@ -476,3 +520,6 @@ define %T2 @simple_struct(%T1 %0, %T2 %1, %T3, %T4) nounwind {
; CHECK-NEXT: .symidx "#simple_struct"
; CHECK-NEXT: .symidx $ientry_thunk$cdecl$m8$i8m8m16m24
; CHECK-NEXT: .word 1
; CHECK-NEXT: .symidx "#cxx_method"
; CHECK-NEXT: .symidx $ientry_thunk$cdecl$i8$i8i8
; CHECK-NEXT: .word 1

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