[WebAssembly] Update function signature mismatch error message

[sbc100]

Summary

We don't start our error messages with capital letters.

Split out from https://reviews.llvm.org/D48394

lld/trunk/test/wasm/fatal-warnings.ll

 ; RUN: llc -filetype=obj %s -o %t.main.o
 ; RUN: llc -filetype=obj %p/Inputs/ret32.ll -o %t.ret32.o
 ; RUN: lld -flavor wasm -o %t.wasm %t.main.o %t.ret32.o 2>&1 | FileCheck %s -check-prefix=CHECK-WARN
 ; RUN: not lld -flavor wasm --fatal-warnings -o %t.wasm %t.main.o %t.ret32.o 2>&1 | FileCheck %s -check-prefix=CHECK-FATAL
 
-; CHECK-WARN: warning: Function type mismatch: ret32
-; CHECK-FATAL: error: Function type mismatch: ret32
+; CHECK-WARN: warning: function signature mismatch: ret32
+; CHECK-FATAL: error: function signature mismatch: ret32
 
 target triple = "wasm32-unknown-unknown"
 
 define hidden void @_start() local_unnamed_addr #0 {
 entry:
   %call = tail call i32 @ret32(i32 1, i64 2, i32 3) #2
   ret void
 }
 
 declare i32 @ret32(i32, i64, i32) local_unnamed_addr #1

lld/trunk/test/wasm/signature-mismatch-weak.ll

 ; RUN: llc -filetype=obj %p/Inputs/weak-symbol1.ll -o %t.weak.o
 ; RUN: llc -filetype=obj %p/Inputs/strong-symbol.ll -o %t.strong.o
 ; RUN: llc -filetype=obj %s -o %t.o
 ; RUN: wasm-ld -o %t.wasm %t.o %t.strong.o %t.weak.o 2>&1 | FileCheck %s
 
 target triple = "wasm32-unknown-unknown"
 
 declare i32 @weakFn() local_unnamed_addr
 
 define void @_start() local_unnamed_addr {
 entry:
   %call = call i32 @weakFn()
   ret void
 }
 
-; CHECK: warning: Function type mismatch: weakFn
+; CHECK: warning: function signature mismatch: weakFn
 ; CHECK-NEXT: >>> defined as () -> I32 in {{.*}}signature-mismatch-weak.ll.tmp.o
 ; CHECK-NEXT: >>> defined as () -> I64 in {{.*}}signature-mismatch-weak.ll.tmp.strong.o

lld/trunk/test/wasm/signature-mismatch.ll

 define hidden void @_start() local_unnamed_addr #0 {
 entry:
   %call = tail call i32 @ret32(i32 1, i64 2, i32 3) #2
   ret void
 }
 
 declare i32 @ret32(i32, i64, i32) local_unnamed_addr #1
 
-; CHECK: error: Function type mismatch: ret32
+; CHECK: error: function signature mismatch: ret32
 ; CHECK-NEXT: >>> defined as (I32, I64, I32) -> I32 in {{.*}}.main.o
 ; CHECK-NEXT: >>> defined as (F32) -> I32 in {{.*}}.ret32.o
 
-; REVERSE: error: Function type mismatch: ret32
+; REVERSE: error: function signature mismatch: ret32
 ; REVERSE-NEXT: >>> defined as (F32) -> I32 in {{.*}}.ret32.o
 ; REVERSE-NEXT: >>> defined as (I32, I64, I32) -> I32 in {{.*}}.main.o

lld/trunk/wasm/SymbolTable.cpp

static void checkFunctionType(const Symbol *Existing, const InputFile *File,
   auto ExistingFunction = dyn_cast<FunctionSymbol>(Existing);
   if (!ExistingFunction) {
     reportTypeError(Existing, File, WASM_SYMBOL_TYPE_FUNCTION);
     return;
   }
 
   const WasmSignature *OldSig = ExistingFunction->getFunctionType();
   if (OldSig && NewSig && *NewSig != *OldSig) {
-    warn("Function type mismatch: " + Existing->getName() +
+    warn("function signature mismatch: " + Existing->getName() +
          "\n>>> defined as " + toString(*OldSig) + " in " +
          toString(Existing->getFile()) + "\n>>> defined as " +
          toString(*NewSig) + " in " + toString(File));
   }
 }
 
 // Check the type of new symbol matches that of the symbol is replacing.
 // For functions this can also involve verifying that the signatures match.