[WebAssembly] Call signExtend to get sign extended register [NFCI]

[jbhateja]

Summary

While analyzing Bug 35064 - Crash in WebAssembly register allocation.
observed this incorrect call.

[sunfish]

Good catch; this change is obviously correct. Would you mind adding a testcase?

[jbhateja]

• Adding a test for signext of function arguments.

lib/Target/WebAssembly/WebAssemblyFastISel.cpp

unsigned WebAssemblyFastISel::getRegForUnsignedValue(const Value *V) {
   MVT::SimpleValueType From = getSimpleType(V->getType());
   MVT::SimpleValueType To = getLegalType(From);
   return zeroExtend(getRegForValue(V), V, From, To);
 }
 
 unsigned WebAssemblyFastISel::getRegForSignedValue(const Value *V) {
   MVT::SimpleValueType From = getSimpleType(V->getType());
   MVT::SimpleValueType To = getLegalType(From);
-  return zeroExtend(getRegForValue(V), V, From, To);
+  return signExtend(getRegForValue(V), V, From, To);
 }
 
 unsigned WebAssemblyFastISel::getRegForPromotedValue(const Value *V,
                                                      bool IsSigned) {
   return IsSigned ? getRegForSignedValue(V) :
                     getRegForUnsignedValue(V);
 }
 

test/CodeGen/WebAssembly/signext-arg.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -march=wasm32 | FileCheck %s
+
+declare i32 @get_int(i16 %arg)
+
+define i32 @func_1(i16 %arg1 , i32 %arg2) #0 {
+; CHECK-LABEL: func_1:
+; CHECK:       # BB#0: # %entry
+; CHECK-NEXT:    i32.const $push1=, 16
+; CHECK-NEXT:    i32.shl $push2=, $0, $pop1
+; CHECK-NEXT:    i32.const $push4=, 16
+; CHECK-NEXT:    i32.shr_s $push3=, $pop2, $pop4
+; CHECK-NEXT:    i32.call $push0=, get_int@FUNCTION, $pop3
+; CHECK-NEXT:    # fallthrough-return: $pop0
+; CHECK-NEXT:    .endfunc
+entry:
+  %retval = call i32 @get_int(i16 signext %arg1)
+  ret i32 %retval
+}
+
+attributes #0 = {noinline nounwind optnone}
+