[PATCH] switch ARM modes in inline assembly

[Greg Fitzgerald]

This patch fixes inline assembly that switches between ARM and Thumb
modes.  Please review:

http://llvm-reviews.chandlerc.com/D2255

Thanks,
Greg


commit 868437b6e13961ad36c15a176c4a9caa726e5042
Author: Greg Fitzgerald <gregf at codeaurora.org>
Date:   Thu Nov 21 15:21:26 2013 -0800

    Fix inline assembly that switches between ARM and Thumb modes

    This patch assumes the inline assembly is responsible for
    restoring the mode.

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
b/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
index 4f927f6..c225183 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
 using namespace llvm;

 namespace {
@@ -114,14 +115,11 @@ void AsmPrinter::EmitInlineAsm(StringRef Str,
const MDNode *LocMDNode,
                                                   OutContext, OutStreamer,
                                                   *MAI));

-  // FIXME: It would be nice if we can avoid createing a new instance of
-  // MCSubtargetInfo here given TargetSubtargetInfo is available. However,
-  // we have to watch out for asm directives which can change subtarget
-  // state. e.g. .code 16, .code 32.
-  OwningPtr<MCSubtargetInfo>
-    STI(TM.getTarget().createMCSubtargetInfo(TM.getTargetTriple(),
-                                             TM.getTargetCPU(),
-                                             TM.getTargetFeatureString()));
+  // Reuse the existing Subtarget, because the AsmParser will
+  // modify it.  For example, when switching between ARM and
+  // Thumb mode.
+  const MCSubtargetInfo* STC = TM.getSubtargetImpl();
+  MCSubtargetInfo* STI = const_cast<MCSubtargetInfo*>(STC);
   OwningPtr<MCTargetAsmParser>
     TAP(TM.getTarget().createMCAsmParser(*STI, *Parser, *MII));
   if (!TAP)
diff --git a/test/CodeGen/ARM/2013-11-22-inline-asm-switch-mode.ll
b/test/CodeGen/ARM/2013-11-22-inline-asm-switch-mode.ll
new file mode 100644
index 0000000..47e75e3
--- /dev/null
+++ b/test/CodeGen/ARM/2013-11-22-inline-asm-switch-mode.ll
@@ -0,0 +1,13 @@
+;RUN:  llc -mtriple=thumbv7-linux-gnueabi -filetype=obj < %s |
llvm-objdump -arch=thumb -d - | FileCheck %s
+
+target triple = "thumbv7--linux-gnueabi"
+
+define hidden void @bah(i8* %start) #0 align 2 {
+  %1 = ptrtoint i8* %start to i32
+  %2 = tail call i32 asm sideeffect "@ Enter ARM Mode  \0A\09adr r3,
1f \0A\09bx  r3 \0A\09.align 2 \0A\09.code 32 \0A1:  push {r7}
\0A\09mov r7, $4 \0A\09svc 0x0 \0A
+  ret void
+}
+; CHECK: $a
+; CHECK-NEXT: 04 70
+; CHECK-NEXT: 2d e5
+