[Bugpoint redesign] Added Pass to Remove Global Variables

Summary:
This pass tries to remove Global Variables, as well as their derived uses. For example if a variable `@x` is used by `%call1` and `%call2`, both these uses and the definition of `@x` are deleted. Moreover if `%call1` or `%call2` are used elsewhere those uses are also deleted, and so on recursively.

I'm still uncertain if this pass should remove derived uses, I'm open to suggestions.

Subscribers: mgorny, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64176

llvm-svn: 368918

3 files changed, 41 insertions, 1 deletions

diff --git a/llvm/test/Reduce/Inputs/remove-global-vars.py b/llvm/test/Reduce/Inputs/remove-global-vars.py
new file mode 100755
index 00000000000..81fbea937dd
--- /dev/null
+++ b/llvm/test/Reduce/Inputs/remove-global-vars.py
@@ -0,0 +1,10 @@
+#!/usr/bin/env python
+
+import sys
+
+input = open(sys.argv[1], "r")
+for line in input:
+  if "@interesting = global" in line:
+    sys.exit(0)
+
+sys.exit(1) # IR isn't interesting
diff --git a/llvm/test/Reduce/remove-funcs.ll b/llvm/test/Reduce/remove-funcs.ll
index 7d6fba86cc3..a0ce24a7f07 100644
--- a/llvm/test/Reduce/remove-funcs.ll
+++ b/llvm/test/Reduce/remove-funcs.ll
@@ -3,7 +3,7 @@
 ;
 ; RUN: llvm-reduce --test %p/Inputs/remove-funcs.py %s
 ; RUN: cat reduced.ll | FileCheck %s
-; REQUIRES: plugins, shell
+; REQUIRES: plugins
 
 ; CHECK-NOT: uninteresting1()
 define i32 @uninteresting1() {
diff --git a/llvm/test/Reduce/remove-global-vars.ll b/llvm/test/Reduce/remove-global-vars.ll
new file mode 100644
index 00000000000..1241cd2c310
--- /dev/null
+++ b/llvm/test/Reduce/remove-global-vars.ll
@@ -0,0 +1,30 @@
+; Test that llvm-reduce can remove uninteresting Global Variables as well as
+; their direct uses (which in turn are replaced with 'undef').
+;
+; RUN: llvm-reduce --test %p/Inputs/remove-global-vars.py %s
+; RUN: cat reduced.ll | FileCheck %s
+; REQUIRES: plugins
+
+; CHECK: @interesting = global
+@interesting = global i32 0, align 4
+; CHECK-NOT: global
+@uninteresting = global i32 1, align 4
+
+define i32 @main() {
+entry:
+  ; CHECK-NOT: load i32, i32* @uninteresting, align 4
+  %0 = load i32, i32* @uninteresting, align 4
+  ; CHECK: store i32 undef, i32* @interesting, align 4
+  store i32 %0, i32* @interesting, align 4
+
+  ; CHECK: load i32, i32* @interesting, align 4
+  %1 = load i32, i32* @interesting, align 4
+  ; CHECK-NOT: store i32 %1, i32* @uninteresting, align 4
+  store i32 %1, i32* @uninteresting, align 4
+
+  ; CHECK: %inc = add nsw i32 undef, 1
+  %inc = add nsw i32 %0, 1
+  ; CHECK: store i32 %inc, i32* @interesting, align 4
+  store i32 %inc, i32* @interesting, align 4
+  ret i32 0
+}