[llvm] r277749 - GlobalISel: also add G_TRUNC to IRTranslator.

[Quentin Colombet via llvm-commits]

Hi Tim,

We were discussing this offline and came to the conclusion that G_TRUNC is a special case of G_EXTRACT.
In other words, we wouldn’t need that instruction.

I understand that for readability that may not be ideal and enum value are cheap, but still I’d like your thoughts on this.

Cheers,
-Quentin

> On Aug 4, 2016, at 11:35 AM, Tim Northover via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> Author: tnorthover
> Date: Thu Aug  4 13:35:17 2016
> New Revision: 277749
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=277749&view=rev
> Log:
> GlobalISel: also add G_TRUNC to IRTranslator.
> 
> Modified:
>    llvm/trunk/lib/CodeGen/GlobalISel/IRTranslator.cpp
>    llvm/trunk/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
> 
> Modified: llvm/trunk/lib/CodeGen/GlobalISel/IRTranslator.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalISel/IRTranslator.cpp?rev=277749&r1=277748&r2=277749&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/GlobalISel/IRTranslator.cpp (original)
> +++ llvm/trunk/lib/CodeGen/GlobalISel/IRTranslator.cpp Thu Aug  4 13:35:17 2016
> @@ -252,13 +252,15 @@ bool IRTranslator::translate(const Instr
>   case Instruction::Call:
>     return translateCall(cast<CallInst>(Inst));
> 
> -  // Casts
> +  // Casts and allied operations
>   case Instruction::BitCast:
>     return translateBitCast(cast<CastInst>(Inst));
>   case Instruction::IntToPtr:
>     return translateCast(TargetOpcode::G_INTTOPTR, cast<CastInst>(Inst));
>   case Instruction::PtrToInt:
>     return translateCast(TargetOpcode::G_PTRTOINT, cast<CastInst>(Inst));
> +  case Instruction::Trunc:
> +    return translateCast(TargetOpcode::G_TRUNC, cast<CastInst>(Inst));
> 
>   // Memory ops.
>   case Instruction::Load:
> 
> Modified: llvm/trunk/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll?rev=277749&r1=277748&r2=277749&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll (original)
> +++ llvm/trunk/test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll Thu Aug  4 13:35:17 2016
> @@ -223,6 +223,19 @@ define i64 @bitcast(i64 %a) {
>   ret i64 %res2
> }
> 
> +; CHECK-LABEL: name: trunc
> +; CHECK: [[ARG1:%[0-9]+]](64) = COPY %x0
> +; CHECK: [[VEC:%[0-9]+]](128) = G_LOAD { <4 x s32>, p0 }
> +; CHECK: [[RES1:%[0-9]+]](8) = G_TRUNC { s8, s64 } [[ARG1]]
> +; CHECK: [[RES2:%[0-9]+]](64) = G_TRUNC { <4 x s16>, <4 x s32> } [[VEC]]
> +define void @trunc(i64 %a) {
> +  %vecptr = alloca <4 x i32>
> +  %vec = load <4 x i32>, <4 x i32>* %vecptr
> +  %res1 = trunc i64 %a to i8
> +  %res2 = trunc <4 x i32> %vec to <4 x i16>
> +  ret void
> +}
> +
> ; CHECK-LABEL: name: load
> ; CHECK: [[ADDR:%[0-9]+]](64) = COPY %x0
> ; CHECK: [[ADDR42:%[0-9]+]](64) = COPY %x1
> 
> 
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