Default stack alignment of x86 NaCl to 16 bytes

[fabiansommer]

Summary

X86 NaCl generally requires the stack to be aligned to 16 bytes.
This change was already implemented in two downstream NaCl compilers
based on llvm.

[dschuff]

(do you want me to land this?)

[fabiansommer]

That would be great, thanks!

llvm/lib/Target/X86/X86Subtarget.cpp

void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
 
   LLVM_DEBUG(dbgs() << "Subtarget features: SSELevel " << X86SSELevel
                     << ", 3DNowLevel " << X863DNowLevel << ", 64bit "
                     << HasX86_64 << "\n");
   if (In64BitMode && !HasX86_64)
     report_fatal_error("64-bit code requested on a subtarget that doesn't "
                        "support it!");
 
-  // Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD and for all
+  // Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD, NaCl, and for all
   // 64-bit targets.  On Solaris (32-bit), stack alignment is 4 bytes
   // following the i386 psABI, while on Illumos it is always 16 bytes.
   if (StackAlignOverride)
     stackAlignment = *StackAlignOverride;
   else if (isTargetDarwin() || isTargetLinux() || isTargetKFreeBSD() ||
-           In64BitMode)
+           isTargetNaCl() || In64BitMode)
     stackAlignment = Align(16);
 
   // Consume the vector width attribute or apply any target specific limit.
   if (PreferVectorWidthOverride)
     PreferVectorWidth = PreferVectorWidthOverride;
   else if (Prefer128Bit)
     PreferVectorWidth = 128;
   else if (Prefer256Bit)

llvm/test/CodeGen/X86/stack-align2.ll

 ; RUN: llc < %s -mcpu=generic -mtriple=i386-linux | FileCheck %s -check-prefix=LINUX-I386
 ; RUN: llc < %s -mcpu=generic -mtriple=i386-kfreebsd | FileCheck %s -check-prefix=KFREEBSD-I386
 ; RUN: llc < %s -mcpu=generic -mtriple=i386-netbsd | FileCheck %s -check-prefix=NETBSD-I386
 ; RUN: llc < %s -mcpu=generic -mtriple=i686-apple-darwin8 | FileCheck %s -check-prefix=DARWIN-I386
 ; RUN: llc < %s -mcpu=generic -mtriple=i386-pc-solaris2.11 | FileCheck %s -check-prefix=SOLARIS-I386
+; RUN: llc < %s -mcpu=generic -mtriple=i386-nacl | FileCheck %s -check-prefix=NACL-I386
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux | FileCheck %s -check-prefix=LINUX-X86_64
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-kfreebsd | FileCheck %s -check-prefix=KFREEBSD-X86_64
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-netbsd | FileCheck %s -check-prefix=NETBSD-X86_64
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-apple-darwin8 | FileCheck %s -check-prefix=DARWIN-X86_64
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-pc-solaris2.11 | FileCheck %s -check-prefix=SOLARIS-X86_64
+; RUN: llc < %s -mcpu=generic -mtriple=x86_64-nacl | FileCheck %s -check-prefix=NACL-X86_64
 
 define i32 @test() nounwind {
 entry:
   call void @test2()
   ret i32 0
 
 ; LINUX-I386:     subl  $12, %esp
 ; KFREEBSD-I386:  subl  $12, %esp
 ; DARWIN-I386:    subl  $12, %esp
+; NACL-I386:      subl  $12, %esp
 ; NETBSD-I386-NOT:  subl  {{.*}}, %esp
 ; SOLARIS-I386-NOT: subl  {{.*}}, %esp
 
 ; LINUX-X86_64:      pushq %{{.*}}
 ; LINUX-X86_64-NOT:  subq {{.*}}, %rsp
 ; DARWIN-X86_64:     pushq %{{.*}}
 ; DARWIN-X86_64-NOT: subq {{.*}}, %rsp
+; NACL-X86_64:       pushq %{{.*}}
+; NACL-X86_64-NOT:   subq {{.*}}, %rsp
 ; NETBSD-X86_64:     pushq %{{.*}}
 ; NETBSD-X86_64-NOT: subq {{.*}}, %rsp
 ; SOLARIS-X86_64:     pushq %{{.*}}
 ; SOLARIS-X86_64-NOT: subq  {{.*}}, %rsp
 ; KFREEBSD-X86_64:     pushq %{{.*}}
 ; KFREEBSD-X86_64-NOT: subq {{.*}}, %rsp
 }
 
 declare void @test2()