Support case-insensitive DMD-style inline assembly. (#4629)

Author: just-harry

gen/asm-x86.h

@@ -25,6 +25,7 @@
 #include "dmd/mangle.h"
 #include "gen/llvmhelpers.h" // printLabelName
 #include <cctype>
+#include "llvm/ADT/StringRef.h"
 
 #ifndef ASM_X86_64
 namespace AsmParserx8632 {
@@ -3703,7 +3704,15 @@ struct AsmProcessor {
       // check for reg first then dotexp is an error?
       if (e->op == EXP::identifier) {
         for (int i = 0; i < N_Regs; i++) {
-          if (ident == regInfo[i].ident) {
+          const auto reg = regInfo[i].ident;
+          const auto matchesRegister = stmt->caseSensitive ?
+            ident == reg :
+#if LDC_LLVM_VER >= 1300
+            reg && llvm::StringRef(ident->toChars()).equals_insensitive(reg->toChars());
+#else
+            reg && llvm::StringRef(ident->toChars()).equals_lower(reg->toChars());
+#endif
+          if (matchesRegister) {
             if (static_cast<Reg>(i) == Reg_ST &&
                 token->value == TOK::leftParenthesis) {
               nextToken();

gen/asmstmt.cpp

@@ -114,8 +114,11 @@ Statement *asmSemantic(AsmStatement *s, Scope *sc) {
   // this is DMD-style asm
   sc->func->hasReturnExp |= 32;
 
+  const auto caseSensitive = s->caseSensitive;
+
   auto ias = createInlineAsmStatement(s->loc, s->tokens);
   s = ias;
+  s->caseSensitive = caseSensitive;
 
   bool err = false;
   llvm::Triple const &t = *global.params.targetTriple;

tests/compilable/c_masm.c

@@ -0,0 +1,13 @@
+// DMD supports case-insensitive register operands for x86 assembly in C files, when targeting Windows.
+// Additionally, a new-line can be used to terminate an instruction.
+
+// REQUIRES: Windows && target_X86
+// RUN: %ldc -mtriple=i686-pc-windows-msvc -c %s
+
+unsigned int subtract(unsigned int a, unsigned int b) {
+    __asm {
+        mov eax, dword ptr [a]
+        mov eDX, dword ptr [b]
+        sub Eax, edx
+    }
+}