[llvm] [RISCV][TTI] Fix crash of non-built-in vector type cost quering. (PR #167258)

[Elvis Wang via llvm-commits]

https://github.com/ElvisWang123 created https://github.com/llvm/llvm-project/pull/167258

For the non-built-in vector type, the RISCV cost model cannot handle this properly. 
So fall back to the BasicTTI for this situation.

Fixes: #166732

>From 05c8fb9e15c56f4bdb52360f22aae5fdec46ea76 Mon Sep 17 00:00:00 2001
From: Elvis Wang <elvis.wang at sifive.com>
Date: Sun, 9 Nov 2025 16:20:03 -0800
Subject: [PATCH] [RISCV][TTI] Fix crash of non-built-in vector type cost
 quering.

For the non-built-in vector type, the RISCV cost model cannot handle
this propely. So fall back to the BasicTTI for this situation.

Fixes: #166732
---
 llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp |  3 ++-
 llvm/test/Analysis/CostModel/RISCV/cast.ll         | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
index 7bc0b5b394828..73387b4999898 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -1683,7 +1683,8 @@ InstructionCost RISCVTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
       !TypeSize::isKnownLE(DL.getTypeSizeInBits(Src),
                            SrcLT.second.getSizeInBits()) ||
       !TypeSize::isKnownLE(DL.getTypeSizeInBits(Dst),
-                           DstLT.second.getSizeInBits()))
+                           DstLT.second.getSizeInBits()) ||
+      SrcLT.first > 1 || DstLT.first > 1)
     return BaseT::getCastInstrCost(Opcode, Dst, Src, CCH, CostKind, I);
 
   // The split cost is handled by the base getCastInstrCost
diff --git a/llvm/test/Analysis/CostModel/RISCV/cast.ll b/llvm/test/Analysis/CostModel/RISCV/cast.ll
index e64bce2d9c9e5..c67702cf8238f 100644
--- a/llvm/test/Analysis/CostModel/RISCV/cast.ll
+++ b/llvm/test/Analysis/CostModel/RISCV/cast.ll
@@ -6239,3 +6239,13 @@ define void @legalization_crash() {
   fptoui <192 x float> undef to <192 x i1>
   ret void
 }
+
+; Test that BitInt cases won't crash at cost model.
+define void @BitInt_crash() {
+; ZVE64X-LABEL: 'BitInt_crash'
+; ZVE64X-NEXT:  Cost Model: Found an estimated cost of 2043 for instruction: %1 = bitcast <16 x i64> undef to <512 x i2>
+; ZVE64X-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
+;
+  bitcast <16 x i64> undef to <512 x i2>
+  ret void
+}