xcore backend: bug when calling countLeadingZeros()

[Robert Lytton]

Hi Duncan,

I've looked through LLVM and clang code.
All other calls to countLeadingZeros(VALUE) are correct - from reasoning the code.

robert

________________________________________
From: llvm-commits-bounces at cs.uiuc.edu [llvm-commits-bounces at cs.uiuc.edu] on behalf of Robert Lytton [robert at xmos.com]
Sent: 02 July 2013 16:08
To: Duncan Sands; llvm-commits at cs.uiuc.edu
Subject: RE: xcore backend: bug when calling countLeadingZeros()

Hi Duncan,

I've not audited the entire code base - sorry.
I'll take a look this evening and let you know....

Robert

________________________________________
From: llvm-commits-bounces at cs.uiuc.edu [llvm-commits-bounces at cs.uiuc.edu] on behalf of Duncan Sands [duncan.sands at gmail.com]
Sent: 02 July 2013 14:45
To: llvm-commits at cs.uiuc.edu
Subject: Re: xcore backend: bug when calling countLeadingZeros()

Hi Robert,

On 02/07/13 14:51, Robert Lytton wrote:
> Hi,
>
> commit b955b0de : "Replace Count{Leading,Trailing}Zeros_{32,64} with
> count{Leading,Trailing}Zeros"
> Added bug to XCore backend.
>
> The type past to countLeadingZeros() now needs to be explicitly cast to 32bit

are other uses of these routines OK?  Did you audit the entire codebase?

Thanks, Duncan.

>
> Below is the patch:
>      llvm/lib/Target/XCore/XCoreISelDAGToDAG.cpp
>      llvm/lib/Target/XCore/XCoreInstrInfo.td
> and test:
>      llvm/test/CodeGen/XCore/zext.ll
>
> robert
>
>
> --- llvm/lib/Target/XCore/XCoreISelDAGToDAG.cpp
> +++ llvm/lib/Target/XCore/XCoreISelDAGToDAG.cpp
> @@ -115,7 +115,7 @@ SDNode *XCoreDAGToDAGISel::Select(SDNode *N) {
>       if (immMskBitp(N)) {
>         // Transformation function: get the size of a mask
>         // Look for the first non-zero bit
> -      SDValue MskSize = getI32Imm(32 - countLeadingZeros(Val));
> +      SDValue MskSize = getI32Imm(32 - countLeadingZeros((uint32_t)Val));
>         return CurDAG->getMachineNode(XCore::MKMSK_rus, dl,
>                                       MVT::i32, MskSize);
>       }
>
>
> --- llvm/lib/Target/XCore/XCoreInstrInfo.td
> +++ llvm/lib/Target/XCore/XCoreInstrInfo.td
> @@ -84,7 +84,7 @@ def msksize_xform : SDNodeXForm<imm, [{
>     // Transformation function: get the size of a mask
>     assert(isMask_32(N->getZExtValue()));
>     // look for the first non-zero bit
> -  return getI32Imm(32 - countLeadingZeros(N->getZExtValue()));
> +  return getI32Imm(32 - countLeadingZeros((uint32_t)N->getZExtValue()));
>   }]>;
>
>   def neg_xform : SDNodeXForm<imm, [{
>
>
> --- /dev/null
> +++ llvm/test/CodeGen/XCore/zext.ll
> @@ -0,0 +1,17 @@
> +; RUN: llc -march=xcore < %s | FileCheck %s
> +;; countLeadingZeros() must be past 32bit types
> +
> +define i32 @f(i1 %a) {
> +entry:
> +; CHECK: zext r0, 1
> +; CHECK: retsp 0
> +  %b= zext i1 %a to i32
> +  ret i32 %b
> +}
> +
> +define i32 @g() {
> +entry:
> +; CHECK: mkmsk r0, 1
> +; CHECK: retsp 0
> +  ret i32 1;
> +}
>
>
>
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