[asan] Optimize accesses to global arrays with constant index

Summary:
Given a global array G[N], which is declared in this CU and has static initializer
avoid instrumenting accesses like G[i], where 'i' is a constant and 0<=i<N.
Also add a bit of stats.

This eliminates ~1% of instrumentations on SPEC2006
and also partially helps when asan is being run together with coverage.

Reviewers: samsonov

Reviewed By: samsonov

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1947

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192794 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 64 insertions, 3 deletions

diff --git a/test/Instrumentation/AddressSanitizer/asan-vs-gvn.ll b/test/Instrumentation/AddressSanitizer/asan-vs-gvn.ll
index da8f541..1087c9a 100644
--- a/test/Instrumentation/AddressSanitizer/asan-vs-gvn.ll
+++ b/test/Instrumentation/AddressSanitizer/asan-vs-gvn.ll
@@ -9,7 +9,7 @@ target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f3
 
 %struct_of_7_bytes_4_aligned = type { i32, i8, i8, i8}
 
-@f = global %struct_of_7_bytes_4_aligned zeroinitializer, align 4
+@f = external global %struct_of_7_bytes_4_aligned , align 4
 
 ; Accessing bytes 4 and 6, not ok to widen to i32 if sanitize_address is set.
 
diff --git a/test/Instrumentation/AddressSanitizer/instrument_global.ll b/test/Instrumentation/AddressSanitizer/instrument_global.ll
index 2c183f5..4717277 100644
--- a/test/Instrumentation/AddressSanitizer/instrument_global.ll
+++ b/test/Instrumentation/AddressSanitizer/instrument_global.ll
@@ -9,12 +9,73 @@ target triple = "x86_64-unknown-linux-gnu"
 ; CHECK: llvm.global_ctors
 ; CHECK: llvm.global_dtors
 
-; CHECK: define internal void @asan.module_ctor
+; Test that we don't instrument global arrays with static initializer
+; indexed with constants in-bounds. But instrument all other cases.
+
+@GlobSt = global [10 x i32] zeroinitializer, align 16  ; static initializer
+@GlobDy = global [10 x i32] zeroinitializer, align 16  ; dynamic initializer
+@GlobEx = external global [10 x i32] , align 16        ; extern initializer
+
+; GlobSt is declared here, and has static initializer -- ok to optimize.
+define i32 @AccessGlobSt_0_2() sanitize_address {
+entry:
+    %0 = load i32* getelementptr inbounds ([10 x i32]* @GlobSt, i64 0, i64 2), align 8
+    ret i32 %0
+; CHECK-LABEL: define i32 @AccessGlobSt_0_2
+; CHECK-NOT: __asan_report
+; CHECK: ret i32 %0
+}
+
+; GlobSt is accessed out of bounds -- can't optimize
+define i32 @AccessGlobSt_0_12() sanitize_address {
+entry:
+    %0 = load i32* getelementptr inbounds ([10 x i32]* @GlobSt, i64 0, i64 12), align 8
+    ret i32 %0
+; CHECK-LABEL: define i32 @AccessGlobSt_0_12
+; CHECK: __asan_report
+; CHECK: ret i32
+}
+
+; GlobSt is accessed with Gep that has non-0 first index -- can't optimize.
+define i32 @AccessGlobSt_1_2() sanitize_address {
+entry:
+    %0 = load i32* getelementptr inbounds ([10 x i32]* @GlobSt, i64 1, i64 2), align 8
+    ret i32 %0
+; CHECK-LABEL: define i32 @AccessGlobSt_1_2
+; CHECK: __asan_report
+; CHECK: ret i32
+}
+
+; GlobDy is declared with dynamic initializer -- can't optimize.
+define i32 @AccessGlobDy_0_2() sanitize_address {
+entry:
+    %0 = load i32* getelementptr inbounds ([10 x i32]* @GlobDy, i64 0, i64 2), align 8
+    ret i32 %0
+; CHECK-LABEL: define i32 @AccessGlobDy_0_2
+; CHECK: __asan_report
+; CHECK: ret i32
+}
+
+; GlobEx is an external global -- can't optimize.
+define i32 @AccessGlobEx_0_2() sanitize_address {
+entry:
+    %0 = load i32* getelementptr inbounds ([10 x i32]* @GlobEx, i64 0, i64 2), align 8
+    ret i32 %0
+; CHECK-LABEL: define i32 @AccessGlobEx_0_2
+; CHECK: __asan_report
+; CHECK: ret i32
+}
+
+
+!llvm.asan.dynamically_initialized_globals = !{!0}
+!0 = metadata !{[10 x i32]* @GlobDy}
+
+; CHECK-LABEL: define internal void @asan.module_ctor
 ; CHECK-NOT: ret
 ; CHECK: call void @__asan_register_globals
 ; CHECK: ret
 
-; CHECK: define internal void @asan.module_dtor
+; CHECK-LABEL: define internal void @asan.module_dtor
 ; CHECK-NOT: ret
 ; CHECK: call void @__asan_unregister_globals
 ; CHECK: ret