Use range metadata instead of introducing selects.

When GlobalOpt has determined that a GlobalVariable only ever has two values,
it would convert the GlobalVariable to a boolean, and introduce SelectInsts
at every load, to choose between the two possible values. These SelectInsts
introduce overhead and other unpleasantness.

This patch makes GlobalOpt just add range metadata to loads from such
GlobalVariables instead. This enables the same main optimization (as seen in
test/Transforms/GlobalOpt/integer-bool.ll), without introducing selects.

The main downside is that it doesn't get the memory savings of shrinking such
GlobalVariables, but this is expected to be negligible.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204076 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 57 insertions, 4 deletions

diff --git a/test/Transforms/GlobalOpt/integer-bool.ll b/test/Transforms/GlobalOpt/integer-bool.ll
index abf5fdd2ef..fc45c82935 100644
--- a/test/Transforms/GlobalOpt/integer-bool.ll
+++ b/test/Transforms/GlobalOpt/integer-bool.ll
@@ -1,20 +1,21 @@
 ; RUN: opt < %s -S -globalopt -instcombine | FileCheck %s
-;; check that global opt turns integers that only hold 0 or 1 into bools.
+;; check that global opt annotates loads from global variales that only hold 0 or 1
+;; such that instcombine can optimize accordingly.
 
 @G = internal addrspace(1) global i32 0
 ; CHECK: @G
 ; CHECK: addrspace(1)
-; CHECK: global i1 false
+; CHECK: global i32 0
 
 define void @set1() {
   store i32 0, i32 addrspace(1)* @G
-; CHECK: store i1 false
+; CHECK: store i32 0
   ret void
 }
 
 define void @set2() {
   store i32 1, i32 addrspace(1)* @G
-; CHECK: store i1 true
+; CHECK: store i32 1
   ret void
 }
 
diff --git a/test/Transforms/GlobalOpt/twostore-gv-range.ll b/test/Transforms/GlobalOpt/twostore-gv-range.ll
new file mode 100644
index 0000000000..84629ddb71
--- /dev/null
+++ b/test/Transforms/GlobalOpt/twostore-gv-range.ll
@@ -0,0 +1,52 @@
+; RUN: opt < %s -S -globalopt | FileCheck %s
+;; check that global opt annotates loads from global variales that have
+;; constant values stored to them.
+
+@G = internal global i32 5
+@H = internal global i32 7
+@I = internal global i32 17
+@J = internal global i32 29
+@K = internal global i32 31
+
+define void @set() {
+  store i32 6, i32* @G
+  store i32 13, i32* @H
+  store i32 16, i32* @I
+  store i32 29, i32* @J
+  store i32 -37, i32* @K
+  ret void
+}
+
+define i32 @getG() {
+; CHECK: %t = load i32* @G, !range [[G:![0-9]+]]
+  %t = load i32* @G
+  ret i32 %t
+}
+define i32 @getH() {
+; CHECK: %t = load i32* @H, !range [[H:![0-9]+]]
+  %t = load i32* @H
+  ret i32 %t
+}
+
+define i32 @getI() {
+; CHECK: %t = load i32* @I, !range [[I:![0-9]+]]
+  %t = load i32* @I
+  ret i32 %t
+}
+
+define i32 @getJ() {
+; CHECK: ret i32 29
+  %t = load i32* @J
+  ret i32 %t
+}
+
+define i32 @getK() {
+; CHECK: %t = load i32* @K, !range [[K:![0-9]+]]
+  %t = load i32* @K
+  ret i32 %t
+}
+
+; CHECK: [[G]] = metadata !{i32 5, i32 7}
+; CHECK: [[H]] = metadata !{i32 7, i32 8, i32 13, i32 14}
+; CHECK: [[I]] = metadata !{i32 16, i32 18}
+; CHECK: [[K]] = metadata !{i32 -37, i32 -36, i32 31, i32 32}