diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -547,9 +547,19 @@
   uint64_t Size = 0;
 
   const MCExpr *ESize = MSD.Symbol->getSize();
-  if (!ESize && Base)
+  if (!ESize && Base) {
+    // For expressions like .set y, x+1, if y's size is unset, inherit from x.
     ESize = Base->getSize();
 
+    // For `.size x, 2; y = x; .size y, 1; z = y; .symver y, y@v1`, z and y@v1's
+    // st_size equals y's. However, `Base` is `x` which will give us 2. Just
+    // detect the SymbolRef case which cover most needs. We'd still get wrong
+    // st_size for `z1 = z` but such chained assignments are rare.
+    if (Symbol.isVariable())
+      if (auto *Sym = dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue(false)))
+        ESize = cast<MCSymbolELF>(Sym->getSymbol()).getSize();
+  }
+
   if (ESize) {
     int64_t Res;
     if (!ESize->evaluateKnownAbsolute(Res, Layout))
diff --git a/llvm/test/MC/ELF/offset.s b/llvm/test/MC/ELF/offset.s
--- a/llvm/test/MC/ELF/offset.s
+++ b/llvm/test/MC/ELF/offset.s
@@ -2,12 +2,13 @@
 
 // Test that a variable declared with "var = other_var + cst" is in the same
 // section as other_var and its value is the value of other_var + cst.
+// In addition, its st_size inherits from other_var.
 
         .data
         .globl	sym_a
-        .size sym_a, 42
         .byte 42
         .type sym_a, @object
+        .size sym_a, 42
 sym_a:
 
 // CHECK:       Symbol {
@@ -62,16 +63,42 @@
 
         .globl sym_f
 sym_f = sym_a + (1 - 1)
+.size sym_f, 41
 // CHECK:       Symbol {
 // CHECK:         Name: sym_f
 // CHECK-NEXT:    Value: 0x1
-// CHECK-NEXT:    Size: 42
+// CHECK-NEXT:    Size: 41
 // CHECK-NEXT:    Binding: Global
 // CHECK-NEXT:    Type: Object
 // CHECK-NEXT:    Other: 0
 // CHECK-NEXT:    Section: .data
 // CHECK-NEXT:  }
 
+/// sym_g's st_size equals sym_f's st_size instead of sym_a's.
+.globl sym_g
+.set sym_g, sym_f
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym_g
+// CHECK-NEXT:    Value: 0x1
+// CHECK-NEXT:    Size: 41
+// CHECK-NEXT:    Binding: Global
+// CHECK-NEXT:    Type: Object
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .data
+// CHECK-NEXT:  }
+
+/// FIXME sym_g's st_size should be 41. This long chained assignments are uncommon.
+.globl sym_h
+.set sym_h, sym_g
+// CHECK-NEXT:  Symbol {
+// CHECK-NEXT:    Name: sym_h
+// CHECK-NEXT:    Value: 0x1
+// CHECK-NEXT:    Size: 0
+// CHECK-NEXT:    Binding: Global
+// CHECK-NEXT:    Type: Object
+// CHECK-NEXT:    Other: 0
+// CHECK-NEXT:    Section: .data
+// CHECK-NEXT:  }
 
         .globl test2_a
         .globl test2_b
@@ -85,6 +112,10 @@
     .long 0
 test2_d = test2_c
 test2_e = test2_d - test2_b
+
+/// sym_f@v1's st_size equals sym_f's st_size.
+.symver sym_f, sym_f@v1
+
 // CHECK:      Symbol {
 // CHECK:        Name: test2_a
 // CHECK-NEXT:   Value: 0x5
@@ -130,3 +161,12 @@
 // CHECK-NEXT:   Other: 0
 // CHECK-NEXT:   Section: Absolute
 // CHECK-NEXT: }
+// CHECK-NEXT: Symbol {
+// CHECK-NEXT:   Name: sym_f@v1
+// CHECK-NEXT:   Value: 0x1
+// CHECK-NEXT:   Size: 41
+// CHECK-NEXT:   Binding: Global
+// CHECK-NEXT:   Type: Object
+// CHECK-NEXT:   Other: 0
+// CHECK-NEXT:   Section: .data
+// CHECK-NEXT: }