diff --git a/llvm/lib/Target/X86/X86Subtarget.cpp b/llvm/lib/Target/X86/X86Subtarget.cpp
--- a/llvm/lib/Target/X86/X86Subtarget.cpp
+++ b/llvm/lib/Target/X86/X86Subtarget.cpp
@@ -258,13 +258,16 @@
     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 Solaris (both
-  // 32 and 64 bit) and for all 64-bit targets.
+  // Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD 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() || isTargetSolaris() ||
-           isTargetKFreeBSD() || In64BitMode)
+  else if (isTargetDarwin() || isTargetLinux() || isTargetKFreeBSD() ||
+           In64BitMode)
     stackAlignment = Align(16);
+  else if (isTargetSolaris() && !In64BitMode)
+    stackAlignment = Align(4);
 
   // Consume the vector width attribute or apply any target specific limit.
   if (PreferVectorWidthOverride)