[PATCH] D89449: [RISCV] Initial infrastructure for code generation of the RISC-V V-extension

Craig Topper via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Nov 24 11:09:29 PST 2020

craig.topper added inline comments.

Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:131
+    addRegisterClass(RISCVVMVTs::vfloat64m1_t, &RISCV::VRRegClass);
+    addRegisterClass(RISCVVMVTs::vfloat64m2_t, &RISCV::VRM2RegClass);
evandro wrote:
> jrtc27 wrote:
> > HsiangKai wrote:
> > > craig.topper wrote:
> > > > Should the types be qualified with hasStdExtD()?  I have the same question for F but it looks like V extension currently implicitly enables the F extension.
> > > I am curious about V should imply F or not. It is vague in the V specification.
> > Currently I read it as no, in that V+Zfinx is a valid combination and would have the FP vector-scalar instructions reading the FP scalar from the "integer' register file.
> V does not imply Zfh, F, D or Zfinx.  However, V supports `half`, `float` and `double` types regardless of F or D or Zfinx.  The V instructions which specify scalar `half`, `float` or `double` operands do require the respective extensions.  At least as I read the spec.  
This doesn't sound like it is just talking about the scalar operands, but maybe I'm reading it wrong.

Vector floating-point instructions require the presence of base scalar floating-point extensions corresponding to the supported vector floating-point element widths.

Profiles supporting 16-bit half-precision floating-point values will also have to implement scalar half-precision floating-point support in the f registers.



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