Teach instCombine to remove malloc+free if malloc's only uses are comparisons

to null.  Patch by Matti Niemenmaa.

llvm-svn: 104871

1 files changed, 16 insertions, 4 deletions

diff --git a/llvm/test/Transforms/InstCombine/malloc-free-delete.ll b/llvm/test/Transforms/InstCombine/malloc-free-delete.ll
index a4b7496ef40..317786fc564 100644
--- a/llvm/test/Transforms/InstCombine/malloc-free-delete.ll
+++ b/llvm/test/Transforms/InstCombine/malloc-free-delete.ll
@@ -1,13 +1,25 @@
-; RUN: opt < %s -instcombine -globaldce -S | FileCheck %s
+; RUN: opt < %s -instcombine -S | FileCheck %s
 ; PR1201
 define i32 @main(i32 %argc, i8** %argv) {
-        %c_19 = alloca i8*              ; <i8**> [#uses=2]
-        %malloc_206 = malloc i8, i32 10         ; <i8*> [#uses=1]
+        %c_19 = alloca i8*
+        %malloc_206 = malloc i8, i32 10
 ; CHECK-NOT: malloc
         store i8* %malloc_206, i8** %c_19
-        %tmp_207 = load i8** %c_19              ; <i8*> [#uses=1]
+        %tmp_207 = load i8** %c_19
         free i8* %tmp_207
 ; CHECK-NOT: free
         ret i32 0
 ; CHECK: ret i32 0
 }
+
+declare i8* @malloc(i32)
+declare void @free(i8*)
+
+define i1 @foo() {
+; CHECK: @foo
+; CHECK-NEXT: ret i1 false
+  %m = call i8* @malloc(i32 1)
+  %z = icmp eq i8* %m, null
+  call void @free(i8* %m)
+  ret i1 %z
+}