[llvm] r294527 - [ARM/AArch ISel] SwiftCC: First parameters that are marked swiftself are not 'this returns'

[Arnold Schwaighofer via llvm-commits]

Hi Hans, Tim

Can we merged this into the 4.0 branch?

This only effects lowering if there is a swiftself attribute — i.e almost zero risk for code that does not use the swift calling convention.


> On Feb 8, 2017, at 2:30 PM, Arnold Schwaighofer via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> Author: arnolds
> Date: Wed Feb  8 16:30:47 2017
> New Revision: 294527
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=294527&view=rev
> Log:
> [ARM/AArch ISel] SwiftCC: First parameters that are marked swiftself are not 'this returns'
> 
> We mark X0 as preserved by a call that passes the returned parameter.
> 
> x0 = ...
> fun(x0) // no implicit def of x0
> 
> This no longer is valid if we pass the parameter in a different register then
> the returned value as is the case with a swiftself parameter (passed in x20).
> 
> x20 = ...
> fun(x20) // there should be an implict def of x8
> 
> rdar://30425845
> 
> Modified:
>    llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
>    llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
>    llvm/trunk/test/CodeGen/AArch64/swiftself.ll
>    llvm/trunk/test/CodeGen/ARM/swiftself.ll
> 
> Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp?rev=294527&r1=294526&r2=294527&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp (original)
> +++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp Wed Feb  8 16:30:47 2017
> @@ -3156,7 +3156,8 @@ AArch64TargetLowering::LowerCall(CallLow
>     }
> 
>     if (VA.isRegLoc()) {
> -      if (realArgIdx == 0 && Flags.isReturned() && Outs[0].VT == MVT::i64) {
> +      if (realArgIdx == 0 && Flags.isReturned() && !Flags.isSwiftSelf() &&
> +          Outs[0].VT == MVT::i64) {
>         assert(VA.getLocVT() == MVT::i64 &&
>                "unexpected calling convention register assignment");
>         assert(!Ins.empty() && Ins[0].VT == MVT::i64 &&
> 
> Modified: llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp?rev=294527&r1=294526&r2=294527&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp (original)
> +++ llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp Wed Feb  8 16:30:47 2017
> @@ -1826,7 +1826,8 @@ ARMTargetLowering::LowerCall(TargetLower
>                          StackPtr, MemOpChains, Flags);
>       }
>     } else if (VA.isRegLoc()) {
> -      if (realArgIdx == 0 && Flags.isReturned() && Outs[0].VT == MVT::i32) {
> +      if (realArgIdx == 0 && Flags.isReturned() && !Flags.isSwiftSelf() &&
> +          Outs[0].VT == MVT::i32) {
>         assert(VA.getLocVT() == MVT::i32 &&
>                "unexpected calling convention register assignment");
>         assert(!Ins.empty() && Ins[0].VT == MVT::i32 &&
> 
> Modified: llvm/trunk/test/CodeGen/AArch64/swiftself.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/swiftself.ll?rev=294527&r1=294526&r2=294527&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/AArch64/swiftself.ll (original)
> +++ llvm/trunk/test/CodeGen/AArch64/swiftself.ll Wed Feb  8 16:30:47 2017
> @@ -65,3 +65,21 @@ define i8* @swiftself_notail(i8* swiftse
>   %res = tail call i8* @swiftself_param(i8* swiftself %addr1)
>   ret i8* %res
> }
> +
> +; We cannot pretend that 'x0' is alive across the thisreturn_attribute call as
> +; we normally would. We marked the first parameter with swiftself which means it
> +; will no longer be passed in x0.
> +declare swiftcc i8* @thisreturn_attribute(i8* returned swiftself)
> +; OPT-LABEL: swiftself_nothisreturn:
> +; OPT-DAG: ldr  x20, [x20]
> +; OPT-DAG: mov [[CSREG:x[1-9].*]], x8
> +; OPT: bl {{_?}}thisreturn_attribute
> +; OPT: str x0, {{\[}}[[CSREG]]
> +; OPT: ret
> +define hidden swiftcc void @swiftself_nothisreturn(i8** noalias nocapture sret, i8** noalias nocapture readonly swiftself) {
> +entry:
> +  %2 = load i8*, i8** %1, align 8
> +  %3 = tail call swiftcc i8* @thisreturn_attribute(i8* swiftself %2)
> +  store i8* %3, i8** %0, align 8
> +  ret void
> +}
> 
> Modified: llvm/trunk/test/CodeGen/ARM/swiftself.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/swiftself.ll?rev=294527&r1=294526&r2=294527&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/ARM/swiftself.ll (original)
> +++ llvm/trunk/test/CodeGen/ARM/swiftself.ll Wed Feb  8 16:30:47 2017
> @@ -63,3 +63,20 @@ define i8* @swiftself_notail(i8* swiftse
>   %res = tail call i8* @swiftself_param(i8* swiftself %addr1)
>   ret i8* %res
> }
> +
> +; We cannot pretend that 'r0' is alive across the thisreturn_attribute call as
> +; we normally would. We marked the first parameter with swiftself which means it
> +; will no longer be passed in r0.
> +declare swiftcc i8* @thisreturn_attribute(i8* returned swiftself)
> +; OPT-LABEL: swiftself_nothisreturn:
> +; OPT-DAG: mov [[CSREG:r[1-9].*]], r0
> +; OPT-DAG: ldr r10, [r10]
> +; OPT: bl  {{_?}}thisreturn_attribute
> +; OPT: str r0, {{\[}}[[CSREG]]
> +define hidden swiftcc void @swiftself_nothisreturn(i8** noalias nocapture sret, i8** noalias nocapture readonly swiftself) {
> +entry:
> +  %2 = load i8*, i8** %1, align 8
> +  %3 = tail call swiftcc i8* @thisreturn_attribute(i8* swiftself %2)
> +  store i8* %3, i8** %0, align 8
> +  ret void
> +}
> 
> 
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