Subzero: Make sure alloca with align=0 is handled correctly.

1. Modify dump() to match LLVM.

2. If it weren't for minimum stack alignment, the alignment code would be broken, so add a test in case the alignment code changes.

BUG= none
R=jvoung@chromium.org, kschimpf@google.com

Review URL: https://codereview.chromium.org/557533003

src/IceTargetLoweringX8632.cpp

diff --git a/src/IceTargetLoweringX8632.cpp b/src/IceTargetLoweringX8632.cpp
index 756508e..c3a6e4d 100644
--- a/src/IceTargetLoweringX8632.cpp
+++ b/src/IceTargetLoweringX8632.cpp
@@ -1118,6 +1118,9 @@
   Operand *TotalSize = legalize(Inst->getSizeInBytes());
   Variable *Dest = Inst->getDest();
   uint32_t AlignmentParam = Inst->getAlignInBytes();
+  // For default align=0, set it to the real value 1, to avoid any
+  // bit-manipulation problems below.
+  AlignmentParam = std::max(AlignmentParam, 1u);
 
   // LLVM enforces power of 2 alignment.
   assert((AlignmentParam & (AlignmentParam - 1)) == 0);