diff --git a/llvm/include/llvm/CodeGen/BasicTTIImpl.h b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
index 61f6564e8cd79..478c228755813 100644
--- a/llvm/include/llvm/CodeGen/BasicTTIImpl.h
+++ b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
@@ -1104,16 +1104,22 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
     auto *SrcVTy = dyn_cast<VectorType>(Src);
     auto *DstVTy = dyn_cast<VectorType>(Dst);
 
+    // The SINT_TO_FP and UINT_TO_FP operations check the legality
+    // based on the src type, not dst type (see SelectionDAGLegalize::LegalizeOp).
+    const bool useSrcType =
+        Opcode == Instruction::SIToFP || Opcode == Instruction::UIToFP;
+    MVT TLIOperationType = useSrcType ? SrcLT.second : DstLT.second;
+
     // If the cast is marked as legal (or promote) then assume low cost.
     if (SrcLT.first == DstLT.first &&
-        TLI->isOperationLegalOrPromote(ISD, DstLT.second))
+        TLI->isOperationLegalOrPromote(ISD, TLIOperationType))
       return SrcLT.first;
 
     // Handle scalar conversions.
     if (!SrcVTy && !DstVTy) {
       // Just check the op cost. If the operation is legal then assume it costs
       // 1.
-      if (!TLI->isOperationExpand(ISD, DstLT.second))
+      if (!TLI->isOperationExpand(ISD, TLIOperationType))
         return 1;
 
       // Assume that illegal scalar instruction are expensive.
@@ -1136,7 +1142,7 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
         // Just check the op cost. If the operation is legal then assume it
         // costs
         // 1 and multiply by the type-legalization overhead.
-        if (!TLI->isOperationExpand(ISD, DstLT.second))
+        if (!TLI->isOperationExpand(ISD, TLIOperationType))
           return SrcLT.first * 1;
       }
 
diff --git a/llvm/test/Analysis/CostModel/AMDGPU/cast.ll b/llvm/test/Analysis/CostModel/AMDGPU/cast.ll
index fc8f5fc393396..da3b01ac54116 100644
--- a/llvm/test/Analysis/CostModel/AMDGPU/cast.ll
+++ b/llvm/test/Analysis/CostModel/AMDGPU/cast.ll
@@ -248,9 +248,9 @@ define void @sitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %A2 = sitofp <4 x i1> %a to <4 x double>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B1 = sitofp <4 x i8> %b to <4 x float>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = sitofp <4 x i8> %b to <4 x double>
-; FAST-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %C1 = sitofp <4 x i16> %c to <4 x float>
+; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = sitofp <4 x i16> %c to <4 x float>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = sitofp <4 x i16> %c to <4 x double>
-; FAST-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
+; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = sitofp <4 x i32> %d to <4 x double>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: ret void
 ;
@@ -261,7 +261,7 @@ define void @sitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = sitofp <4 x i8> %b to <4 x double>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = sitofp <4 x i16> %c to <4 x float>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = sitofp <4 x i16> %c to <4 x double>
-; SLOW-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
+; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = sitofp <4 x i32> %d to <4 x double>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: ret void
 ;
@@ -270,9 +270,9 @@ define void @sitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %A2 = sitofp <4 x i1> %a to <4 x double>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B1 = sitofp <4 x i8> %b to <4 x float>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = sitofp <4 x i8> %b to <4 x double>
-; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %C1 = sitofp <4 x i16> %c to <4 x float>
+; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = sitofp <4 x i16> %c to <4 x float>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = sitofp <4 x i16> %c to <4 x double>
-; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
+; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = sitofp <4 x i32> %d to <4 x double>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
@@ -283,7 +283,7 @@ define void @sitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = sitofp <4 x i8> %b to <4 x double>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = sitofp <4 x i16> %c to <4 x float>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = sitofp <4 x i16> %c to <4 x double>
-; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
+; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = sitofp <4 x i32> %d to <4 x float>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = sitofp <4 x i32> %d to <4 x double>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
@@ -326,9 +326,9 @@ define void @uitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %A2 = uitofp <4 x i1> %a to <4 x double>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B1 = uitofp <4 x i8> %b to <4 x float>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = uitofp <4 x i8> %b to <4 x double>
-; FAST-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %C1 = uitofp <4 x i16> %c to <4 x float>
+; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = uitofp <4 x i16> %c to <4 x float>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = uitofp <4 x i16> %c to <4 x double>
-; FAST-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
+; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = uitofp <4 x i32> %d to <4 x double>
 ; FAST-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: ret void
 ;
@@ -339,7 +339,7 @@ define void @uitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = uitofp <4 x i8> %b to <4 x double>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = uitofp <4 x i16> %c to <4 x float>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = uitofp <4 x i16> %c to <4 x double>
-; SLOW-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
+; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = uitofp <4 x i32> %d to <4 x double>
 ; SLOW-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: ret void
 ;
@@ -348,9 +348,9 @@ define void @uitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %A2 = uitofp <4 x i1> %a to <4 x double>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B1 = uitofp <4 x i8> %b to <4 x float>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = uitofp <4 x i8> %b to <4 x double>
-; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %C1 = uitofp <4 x i16> %c to <4 x float>
+; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = uitofp <4 x i16> %c to <4 x float>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = uitofp <4 x i16> %c to <4 x double>
-; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
+; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = uitofp <4 x i32> %d to <4 x double>
 ; FAST-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
@@ -361,7 +361,7 @@ define void @uitofp4(<4 x i1> %a, <4 x i8> %b, <4 x i16> %c, <4 x i32> %d) {
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %B2 = uitofp <4 x i8> %b to <4 x double>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C1 = uitofp <4 x i16> %c to <4 x float>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %C2 = uitofp <4 x i16> %c to <4 x double>
-; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
+; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D1 = uitofp <4 x i32> %d to <4 x float>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %D2 = uitofp <4 x i32> %d to <4 x double>
 ; SLOW-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;