From 2288e15ec669ed852296a8ab2cbda3043866b009 Mon Sep 17 00:00:00 2001
From: Walter Bright <walter@walterbright.com>
Date: Sun, 29 Dec 2024 23:52:39 -0800
Subject: [PATCH] fix #20621 Comparing addresses of rvalue reference parameters
 not correct

---
 compiler/src/dmd/constfold.d     | 13 ++++++++++++-
 compiler/src/dmd/e2ir.d          |  2 +-
 compiler/test/runnable/rvalue1.d |  2 ++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/compiler/src/dmd/constfold.d b/compiler/src/dmd/constfold.d
index 1578ef770a09..9d5aa96416b5 100644
--- a/compiler/src/dmd/constfold.d
+++ b/compiler/src/dmd/constfold.d
@@ -806,6 +806,7 @@ UnionExp Equal(EXP op, const ref Loc loc, Type type, Expression e1, Expression e
 
 UnionExp Identity(EXP op, const ref Loc loc, Type type, Expression e1, Expression e2)
 {
+    //printf("Identity %s %s\n", e1.toChars(), e2.toChars());
     UnionExp ue = void;
     int cmp;
     if (e1.op == EXP.null_)
@@ -820,7 +821,17 @@ UnionExp Identity(EXP op, const ref Loc loc, Type type, Expression e1, Expressio
     {
         SymOffExp es1 = e1.isSymOffExp();
         SymOffExp es2 = e2.isSymOffExp();
-        cmp = (es1.var == es2.var && es1.offset == es2.offset);
+        cmp = es1.offset == es2.offset;
+        if (cmp)
+        {
+            cmp = es1.var == es2.var;
+            if (!cmp && (es1.var.isParameter() || es2.var.isParameter()))
+            {
+                // because of ref's, they may still be the same, we cannot tell
+                cantExp(ue);
+                return ue;
+            }
+        }
     }
     else
     {
diff --git a/compiler/src/dmd/e2ir.d b/compiler/src/dmd/e2ir.d
index e120df28d3a7..c48b7265f545 100644
--- a/compiler/src/dmd/e2ir.d
+++ b/compiler/src/dmd/e2ir.d
@@ -103,7 +103,7 @@ bool ISX64REF(Declaration var)
 
     if (var.isParameter())
     {
-        if (target.os == Target.OS.Windows && target.isX86_64)
+        if (target.os == Target.OS.Windows /*&& target.isX86_64*/)
         {
             /* Use Microsoft C++ ABI
              * https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention?view=msvc-170#parameter-passing
diff --git a/compiler/test/runnable/rvalue1.d b/compiler/test/runnable/rvalue1.d
index 07ea4270b881..f8134f718a9f 100644
--- a/compiler/test/runnable/rvalue1.d
+++ b/compiler/test/runnable/rvalue1.d
@@ -55,6 +55,8 @@ struct S4
 {
     void* p;
 
+    this(ref S4) { }
+
     this(S4 s)
     {
         assert(&s is &x); // confirm the rvalue reference