[clang] [llvm] [RISCV][llvm] Support fixed-length vector inline assembly constraints (PR #150724)

[Craig Topper via llvm-commits]

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@@ -23146,10 +23152,24 @@ RISCVTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
           &RISCV::VRN2M4NoV0RegClass}) {
       if (TRI->isTypeLegalForClass(*RC, VT.SimpleTy))
         return std::make_pair(0U, RC);
+
+      if (VT.isFixedLengthVector() && Subtarget.useRVVForFixedLengthVectors()) {
+        MVT ContainerVT = getContainerForFixedLengthVector(VT);
+        if (TRI->isTypeLegalForClass(*RC, ContainerVT))
+          return std::make_pair(0U, RC);
+      }
     }
   } else if (Constraint == "vm") {
     if (TRI->isTypeLegalForClass(RISCV::VMV0RegClass, VT.SimpleTy))
       return std::make_pair(0U, &RISCV::VMV0RegClass);
+
+    if (VT.isFixedLengthVector() && Subtarget.useRVVForFixedLengthVectors()) {
+      MVT ContainerVT = getContainerForFixedLengthVector(VT);
+      // VT here is coerced to vector with i8 elements, so we need to check if
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topperc wrote:

I don't understand this comment. Where is it coerced?

https://github.com/llvm/llvm-project/pull/150724