commit 87f80c128a9e2bc95829cd1aac2bbc3c44b44ac1
author Andrew Scull <ascull@google.com> Mon Jul 20 10:19:16 2015 -0700
committer Andrew Scull <ascull@google.com> Mon Jul 20 10:19:16 2015 -0700
tree cea1ac72883720f673fc531e6a1b0dab8e03bb59
parent 53483691eba6e23de63afe0579b436002d06d187

Introduction of improved switch lowering.

This includes the high level analysis of switches, the x86 lowering,
the repointing of targets in jump tables and ASM emission of jump
tables.

The technique uses jump tables, range test and binary search with
worst case O(lg n) which improves the previous worst case of O(n)
from a sequential search.

Use is hidden by the --adv-switch flag as the IAS emission still
needs to be implemented.

BUG=None
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/1234803007.

src/IceTypes.cpp

diff --git a/src/IceTypes.cpp b/src/IceTypes.cpp
index 2099cb9..dd06b1e 100644
--- a/src/IceTypes.cpp
+++ b/src/IceTypes.cpp
@@ -30,7 +30,7 @@
 
 // Define a temporary set of enum values based on ICETYPE_TABLE
 enum {
-#define X(tag, size, align, elts, elty, str) _table_tag_##tag,
+#define X(tag, sizeLog2, align, elts, elty, str) _table_tag_##tag,
   ICETYPE_TABLE
 #undef X
       _enum_table_tag_Names
@@ -44,7 +44,7 @@
       _enum_props_table_tag_Names
 };
 // Assert that tags in ICETYPE_TABLE are also in ICETYPE_PROPS_TABLE.
-#define X(tag, size, align, elts, elty, str)                                   \
+#define X(tag, sizeLog2, align, elts, elty, str)                               \
   static_assert(                                                               \
       (unsigned)_table_tag_##tag == (unsigned)_props_table_tag_##tag,          \
       "Inconsistency between ICETYPE_PROPS_TABLE and ICETYPE_TABLE");
@@ -63,7 +63,7 @@
 
 // Define constants for each element size in ICETYPE_TABLE.
 enum {
-#define X(tag, size, align, elts, elty, str) _table_elts_##tag = elts,
+#define X(tag, sizeLog2, align, elts, elty, str) _table_elts_##tag = elts,
   ICETYPE_TABLE
 #undef X
       _enum_table_elts_Elements = 0
@@ -83,7 +83,7 @@
 #undef X
 
 struct TypeAttributeFields {
-  size_t TypeWidthInBytes;
+  int8_t TypeWidthInBytesLog2;
   size_t TypeAlignInBytes;
   size_t TypeNumElements;
   Type TypeElementType;
@@ -91,8 +91,8 @@
 };
 
 const struct TypeAttributeFields TypeAttributes[] = {
-#define X(tag, size, align, elts, elty, str)                                   \
-  { size, align, elts, elty, str }                                             \
+#define X(tag, sizeLog2, align, elts, elty, str)                               \
+  { sizeLog2, align, elts, elty, str }                                         \
   ,
     ICETYPE_TABLE
 #undef X
@@ -133,10 +133,15 @@
 }
 
 size_t typeWidthInBytes(Type Ty) {
+  int8_t Shift = typeWidthInBytesLog2(Ty);
+  return (Shift < 0) ? 0 : 1 << Shift;
+}
+
+int8_t typeWidthInBytesLog2(Type Ty) {
   size_t Index = static_cast<size_t>(Ty);
   if (Index < IceType_NUM)
-    return TypeAttributes[Index].TypeWidthInBytes;
-  llvm_unreachable("Invalid type for typeWidthInBytes()");
+    return TypeAttributes[Index].TypeWidthInBytesLog2;
+  llvm_unreachable("Invalid type for typeWidthInBytesLog2()");
   return 0;
 }