[llvm] [RISCV] Don't look through EXTRACT_ELEMENT in lowerScalarInsert if the element types are different. (PR #78668)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-risc-v

Author: Craig Topper (topperc)

<details>
<summary>Changes</summary>

If the element type of we're extracting doesn't match the type we're inserting into, we can't directly insert or extract the subvector.

---
Full diff: https://github.com/llvm/llvm-project/pull/78668.diff


2 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVISelLowering.cpp (+16-12) 
- (modified) llvm/test/CodeGen/RISCV/rvv/fold-binary-reduce.ll (+23) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 019ea93aac9dc6..b41e2f40dc72f0 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -4040,19 +4040,23 @@ static SDValue lowerScalarInsert(SDValue Scalar, SDValue VL, MVT VT,
   if (Scalar.getOpcode() == ISD::EXTRACT_VECTOR_ELT &&
       isNullConstant(Scalar.getOperand(1))) {
     SDValue ExtractedVal = Scalar.getOperand(0);
-    MVT ExtractedVT = ExtractedVal.getSimpleValueType();
-    MVT ExtractedContainerVT = ExtractedVT;
-    if (ExtractedContainerVT.isFixedLengthVector()) {
-      ExtractedContainerVT = getContainerForFixedLengthVector(
-          DAG, ExtractedContainerVT, Subtarget);
-      ExtractedVal = convertToScalableVector(ExtractedContainerVT, ExtractedVal,
-                                             DAG, Subtarget);
-    }
-    if (ExtractedContainerVT.bitsLE(VT))
-      return DAG.getNode(ISD::INSERT_SUBVECTOR, DL, VT, Passthru, ExtractedVal,
+    // The element types must be the same.
+    if (ExtractedVal.getValueType().getVectorElementType() ==
+        VT.getVectorElementType()) {
+      MVT ExtractedVT = ExtractedVal.getSimpleValueType();
+      MVT ExtractedContainerVT = ExtractedVT;
+      if (ExtractedContainerVT.isFixedLengthVector()) {
+        ExtractedContainerVT = getContainerForFixedLengthVector(
+            DAG, ExtractedContainerVT, Subtarget);
+        ExtractedVal = convertToScalableVector(ExtractedContainerVT,
+                                               ExtractedVal, DAG, Subtarget);
+      }
+      if (ExtractedContainerVT.bitsLE(VT))
+        return DAG.getNode(ISD::INSERT_SUBVECTOR, DL, VT, Passthru,
+                           ExtractedVal, DAG.getConstant(0, DL, XLenVT));
+      return DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, VT, ExtractedVal,
                          DAG.getConstant(0, DL, XLenVT));
-    return DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, VT, ExtractedVal,
-                       DAG.getConstant(0, DL, XLenVT));
+    }
   }
 
 
diff --git a/llvm/test/CodeGen/RISCV/rvv/fold-binary-reduce.ll b/llvm/test/CodeGen/RISCV/rvv/fold-binary-reduce.ll
index 8fd8c2548ff34d..351c0bab9dca89 100644
--- a/llvm/test/CodeGen/RISCV/rvv/fold-binary-reduce.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/fold-binary-reduce.ll
@@ -343,3 +343,26 @@ declare i64 @llvm.smax.i64(i64, i64)
 declare i64 @llvm.smin.i64(i64, i64)
 declare float @llvm.maxnum.f32(float ,float)
 declare float @llvm.minnum.f32(float ,float)
+
+define void @crash(<2 x i32> %0) {
+; CHECK-LABEL: crash:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
+; CHECK-NEXT:    vmv.x.s a0, v8
+; CHECK-NEXT:    vsetivli zero, 4, e16, mf2, ta, ma
+; CHECK-NEXT:    vmv.v.i v8, 0
+; CHECK-NEXT:    vmv.s.x v9, a0
+; CHECK-NEXT:    vredsum.vs v8, v8, v9
+; CHECK-NEXT:    vmv.x.s a0, v8
+; CHECK-NEXT:    sb a0, 0(zero)
+; CHECK-NEXT:    ret
+entry:
+  %1 = extractelement <2 x i32> %0, i64 0
+  %2 = tail call i16 @llvm.vector.reduce.add.v4i16(<4 x i16> zeroinitializer)
+  %3 = zext i16 %2 to i32
+  %op.rdx = add i32 %1, %3
+  %conv18.us = trunc i32 %op.rdx to i8
+  store i8 %conv18.us, ptr null, align 1
+  ret void
+}
+declare i16 @llvm.vector.reduce.add.v4i16(<4 x i16>)

``````````

</details>


https://github.com/llvm/llvm-project/pull/78668